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Step by Step

Vitrectomy

Step by Step

Vitrectomy Second Edition

José J Martinez-Toldos md phd

Chief Service of Ophthalmology Hospital General Universitario de Elche Alicante, Spain

Jairo E Hoyos md phd

Physician of Ophthalmology Instituto Oftalmologico Hoyos Sabadell, Barcelona, Spain

Foreword Borja Corcóstegui

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD New Delhi • London • Philadelphia • Panama

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Website: www.jaypeebrothers.com Website: www.jaypeedigital.com © 2013, Jaypee Brothers Medical Publishers All rights reserved. No part of this book may be reproduced in any form or by any means without the prior permission of the publisher. Inquiries for bulk sales may be solicited at: [email protected] This book has been published in good faith that the contents provided by the contributors contained herein are original, and is intended for educational purposes only. While every effort is made to ensure accuracy of information, the publisher and the editors specifically disclaim any damage, liability, or loss incurred, directly or indirectly, from the use or application of any of the contents of this work. If not specifically stated, all figures and tables are courtesy of the editors. Where appropriate, the readers should consult with a specialist or contact the manufacturer of the drug or device. Step By Step Vitrectomy First Edition: 2006 Second Edition: 2013 ISBN 978-93-5090-354-4 Printed at

Dedicated to All vitreoretinal surgeons

Contributors

Amparo Navea Tejerina MD PhD Chairman of Vitreoretinal Division Fundación Oftalmologíca del Meditarraneo Valencia, Spain Ana Boixadera MD PhD Department of Ophthalmology Hospital Vall d´Hebron Barcelona, Spain Ana Orive MD Physician of Ophthalmology Hospital Alcorcon Madrid, Spain Anna Grabowoska MD Resident of Ophthalmology Hospital Universitario la Paz Madrid, Spain Anniken Burés MD Physician of Ophthalmology Instituto de Microcirugía Ocular Barcelona, Spain Beatriz Manzano MD Physician of Ophthalmology Hospital Universitario la Paz Madrid, Spain Carlos Mateo MD PhD Vitreoretinal Surgery Instituto Microcirugía Ocular Barcelona, Spain

Carme Guardia MD Physician of Ophthalmology in the Vitreoretinal Section Parc Taulí Hospital Sabadell, Barcelona Vitreoretinal Surgeon in the Instituto Oftalmologico Hoyos Sabadell, Barcelona, Spain Carmen Desco MD Physician of Ophthalmology in the Vitreoretinal Section Fundación Oftalmologíca del Meditarraneo Valencia, Spain Cristian Fernández-Martínez MD Vitreoretinal Surgery Physician Hospital General Universitario de Elche Alicante, Spain David Salom MD Vitreoretinal Surgery Physician of Ophthalmology Hospital Universitario y Politécnico la Fe Valencia, Spain Elena palacios MD Physician of Ophthalmology in the Vitreoretinal Section Fundación Oftalmologíca del Meditarraneo Valencia, Spain

Step by Step Vitrectomy

viii Enrique López-Sánchez Vitreoretinal Surgery Hospital Arnau de Vilanova Valencia, Spain

Javier Orduña MD Physician of Ophthalmology Hospital Alcorcon Madrid, Spain

Fernando M penha MD Vitreoretinal Diseases Sector Vision Institute Department of Ophthalmology Federal University of São Paulo São Paulo, Brazil

Jorge Mataix MD Physician of Ophthalmology in the Vitreoretinal Section Fundación Oftalmologíca del Meditarraneo Valencia, Spain

Félix Armadá Maresca MD PhD Head of Section Vitreoretinal Surgery Hospital Universitario la Paz Madrid, Spain

Josefina Bañuelos Bañuelos MD PhD Vitreoretinal Surgery Hospital Alcorcon Madrid, Spain

J Fernando Arevalo MD FACS Executive Vice-President of the Pan-American Association of Ophthalmology Chief of Vitreoretinal Division The King Khaled Eye Specialist Hospital, Riyadh, Kingdom of Saudi Arabia, KKESH/WEI Adjunct Professor of Ophthalmology Wilmer Eye Institute The Johns Hopkins University Baltimore, MD, USA Jairo E Hoyos MD Physician of Ophthalmology Instituto Oftalmologico Hoyos Sabadell, Barcelona, Spain Jaume Catalá MD Physician of Ophthalmology Instituto Oftalmologico HoyosSabadell Barcelona, Spain Javier Montero Moreno MD Ophthalmology Unit Pio del Rio Hortega University Valladolid, Spain

José García-Arumí MD PhD Professor of Ophthalmology, UAB Head of Ophthalmology Hospital Valle Hebrón, Barcelona, Spain Instituto de microcirugía Ocular Barcelona, Spain José J Martínez-Toldos MD PhD Chief Service of Ophthalmology Hospital General Universitario de Elche Alicante, Spain José María Ruiz Moreno MD PhD Professor of Ophthalmology Castilla la Mancha University Albacete Medical School Vissum, Alicante Institute of Ophthalmology Alicante, Spain Juan Carlos Elvira MD PhD Chief of Ophthalmology Hospital del Vilanolopo Elche Alicante, Spain Laura Distefano MD Department of Ophthalmology Hospital Vall d´Hebron Barcelona, Spain

Contributors

ix Manuel Diaz-Llopís MD PhD Professor of Ophthalmology University of Valencia Hospital Universitario y Politécnico la Fe de Valencia Valencia, Spain María Granados MD Physician of Ophthalmology Hospital Universitario la Paz Madrid, Spain Mauricio Maia MD PhD Vitreoretinal Disease Unit Brazilian Institute of Fighting against Blindess and Hospital de Olhos Oeste Paulista Assis and Presidente Prundente Sao Paulo, Brazil Melania Cigales MD PhD Physician of Ophthalmology Instituto Oftalmologico Hoyos Sabadell, Barcelona, Spain Miguel Angel Zapata MD Department of Ophthalmology Hospital Vall d´Hebron Barcelona, Spain Natalia pastora MD Physician of Ophthalmology Hospital Universitario la Paz, Madrid, Spain patricia Martínez-García MD Physician of Ophthalmology Hospital Alcorcon Madrid, Spain

patricia Udaondo MD Physician of Ophthalmology Vitreoretinal Surgery Hospital Universitarioy Politécnico la Fe Valencia, Spain Reinardo A García MD Vitreoretinal Section Clínica Oftalmológica Centro Caracas Caracas, Venezuela Salvador Garcia-Delpech MD Physician of Ophthalmology Hospital Universitarioy Politécnico la Fe Valencia, Spain Verónica Oria MD Vitreoretinal Section Clínica Oftalmológica Centro Caracas Caracas, Venezuela Vicente Chaqués Alepuz MD PhD Head of Ophthalmology Hospital Arnau de Vilanova Valencia, Spain Vicente Martinez-Castillo MD PhD Vitreoretinal Surgery Hospital Vall d´Hebron Barcelona, Spain

Foreword

Once again, José Juan Martinez-Toldos provides us with a book on vitreoretinal surgery, which is a compilation of the experience of several authors under his supervision in an effort to unify criteria. This edition covers all aspects of vitreoretinal surgery, from anatomy of the interior eye, the presurgery examination of the patient, complementary tests, passing through an exhaustive analysis of instrumentation and its different uses, to the treatment of commonly-faced problems, such as diabetic retinopathy, retinal detachment with or without proliferative vitreoretinopathy (PVR) and macular disease. New to this edition, we find chapters on 27 gauge vitrectomy instruments, enzyme lysis or new products that are still under investigation or development. The chapter on the organization of the surgical area will be of interest to those freshly starting out in this discipline. Although theoretical aspects are key to this work, the photographs and footage of surgery provided will be of great practical use to the surgeon who wishes to analyze and improve on given surgical steps or procedures. Only by examining images of a surgical intervention will we be able to discover how a surgeon resolves a given situation or observe the finer details of his/her maneuver, the risks assumed, in other words, the quality of surgery. Personally, I am a great believer in watching surgery in action since it enables us to observe the capacity to resolve the different cases at each moment, in which some have surprisingly made fundamental errors. Jose Juan has been a good friend of mine since his beginnings in ophthalmology. His capacity for work and study, his fight until the end with each case, and his limitless honesty makes him the ideal person for such an ambitious venture. We hope that it will help young surgeons acquire an indepth knowledge of their profession without getting caught up in the current search for ever smaller instruments as the only pursuit of this type of surgery. Borja Corcóstegui md phD Professor of Ophthalmology ESASO (European School for Advanced Studies in Ophthalmology) Lugano, Switzerland Chairman Instituto de Microcirugia Ocular Barcelona, Spain

Foreword

More than six years have passed since the first edition of Step by Step Basic Vitrectomy. As expected, vitrectomy has continued its fast development and it is at this point that an update of its techniques an understanding is required. In this edition, we discuss the new high-speed vitreotomes with duty cycles that provide good control of eye tissues and thus avoid retinal damage. We describe the new techniques that have appeared on the scene such as 27 gauge vitrectomy. This approach allows a 0.4 mm incision, minimizing ocular pain and along with the use of valved trocars, enables a vitrectomy with little fluid and scarce turbulence within the eye. Also discussed are the new 23, 25 and 27 gauge instruments and the new illumination systems that allow the surgeon to more safely work inside the ocular globe fulfilling the prerequisite of good vision needed for a good vitrectomy. The new chapters introduced in this update include one on vitrectomy for eye trauma and another on the knowledge needed to efficiently treat patients with myopia. Besides these, the reader will find chapters dealing with new drugs, such as antiangiogenic compounds, sustained-release agents, and with current trends in enzymatic vitrectomy. As in its first edition, rather than an extensive review of the art state, the objective of this book is to provide a descriptive reference of all the necessary procedures and how these should be used in basic vitreoretinal surgery along with our opinions and personal preferences. We have also prepared a video showing the different surgical procedures featuring experts who describe the techniques of tissue staining, removing epiretinal and internal limiting membranes, treating the various forms of proliferative retinopathy, lensectomy procedures, how to manage myopic maculoschisis and the use of new medications. Finally, we would like to remind all vitreoretinal surgeons of the need to constantly improve our knowledge of the technique, which day-by-day is becoming safer and offers better outcomes to our patients. José J Martinez-Toldos Jairo E Hoyos

Preface to the Second Edition

The topic of vitrectomy includes both diagnostic and therapeutic approaches and requires a profound understanding of the anatomy and physiology of the eye. The vitreoretinal surgeon needs to master classic diagnostic tools, such as indirect ophthalmoscopy and examination of the retina and vitreous through contact and noncontact biomicroscopy. More recent developments have also led to a need for a sound knowledge of ultrasonography, and optical coherence tomography, especially its prognostic use for macular problems. Any specialist new to the technique will be certainly overwhelmed by the speed at which the field advances to constantly generate new visualization systems, microscopes, vitrectomy machines, minimum incision approaches (23, 25 gauges), hand-held instruments, and tissue stains and drugs. Embarking on a vitrectomy without the appropriate prior knowledge is the road to disaster, since the most simple of cases may become complicated and could lead to the loss of vision with all the legal implications this entails. This book offers to the reader descriptions of all the procedures of basic vitreoretinal surgery and how they should be used. These step-by-step descriptions are related from our own experience and include our opinion about which methods should be preferentially used for each step. Apart from its illustrations and photographs, several video recordings are provided on two DVDs in which the reader will be able to see the most frequently used procedures, such as those performed to treat cataract surgery complications, retinal detachment, problems related to diabetic retinopathy and macular disease, along with the use of tissue dyes, such as brilliant blue, trypan blue and triamcinolone, to visualize the eye structures during surgery. Finally, we recommend continuing education through the different specialist journals and Internet sites offering information and videos on novel surgeries as the best way to refine and improve this extraordinary surgical technique. José J Martinez-Toldos Jairo E Hoyos

Preface to the First Edition

Vitrectomy is a wide subject that includes diagnostic and therapeutic approaches as well as the need for an in-depth understanding of the anatomical and physiological features of the eye. The vitreoretinal specialist needs to be able to dominate classic diagnostic tools such as indirect ophthalmoscopy and explore the vitreous and retina through contact lens and noncontact biomicroscopy. Developments in the last few years have also meant a need to be adequately handle the use of ocular ultrasonography and optical coherence tomography. Any surgeon embarking on the technique of vitrectomy will certainly be overwhelmed by the staggering recent advances made in the field, along with the vast array of approaches offered by the different visualization systems, high cutting speed vitrectomy machines, minimal incision procedures (23–25 gauge), new manual instruments, tissue stains and intraocular drugs. This everincreasing surge of information, besides being difficult to assimilate, requires the appropriate ordering of all these new concepts to tackle this challenging and extraordinary technique. In preparing this book, we have tried to provide descriptions of all the elements needed for basic vitreoretinal surgery. These descriptions are presented according to our own experience and from the perspective of our personal thoughts on which procedure should be used in each step undertaken. In no case would we recommend initiating a vitrectomy without first completing all the preceding requisites, since the simplest of cases can in theory become complicated and lead to vision loss with all the legal implications this entails. Apart from the images and photographs obtained during surgery, we also include several video recordings on a CD, in which the reader may directly observe the most common maneuvers performed, such as those undertaken to rescue complications arising from cataract surgery, treating different types of detached retina, diabetic retinopathy, macular disease, the use of tissue stains, such as indocyanine green and trypan blue, and the use of triamcinolone in vitreoretinal surgery. Finally, we would like to point out to the vitreoretinal surgeon, the importance of an open mind to keep up with the speed of developments in this field.

José J Martinez-Toldos Jairo E Hoyos

Contents

1. Surgical Anatomy

1

Cristian Fernández-Martinez, José Juan Martinez-Toldos

Introduction 1 Anatomy of the Vitreous 1

Vitreous Base and Vitreoretinal Interface 2

Anatomical Distances in Vitrectomy 4 Crystalline Lens 4;

Extraocular Muscles 4;

Ciliary Body 5;

Blood Vessels 5

2. presurgery Examination

9

Manolo Baeza Diaz, José Juan Martinez-Toldos

Medical History 9 Visual Acuity 9

Pupil Reflexes 9; Color Perception 10; Microscopy 10; Tonometry 10

Examining the Fundus 11

Indirect Ophthalmoscopy 11;

Vascular Entoptic Test 10;

Slit Lamp

Biomicroscopy of the Retina 11

Ultrasonography 11 Vitreous Disorder 12

Fluorescein Angiography 16 Electrophysiology 17 Electroretinography 17;

Evoked Visual Potentials 17

3. Vitrectomy and Optical Coherence Tomography

19

David Salom, Patricia Udaondo, Manuel Díaz Llopis, José Juan Martínez-Toldos

Introduction 19 Optical Coherence Tomography in Macular Holes 20 Optical Coherence Tomography in Epiretinal Membranes 21 Optical Coherence Tomography in Vitreoretinal Traction Syndrome 22 Intraoperative 25

4. Anesthesia

28

Manuel Baeza, José Juan Martínez-Toldos

Introduction 28 Types of Anesthesia 29

General Anesthesia 29; Local Anesthesia 30; Retrobulbar Block 33; Peribulbar Anesthesia 35; Sub-Tenon’s Anesthesia 36

5. Instrumentation

43

José Juan Martínez-Toldos, Cristian Fernández-Martínez

5.1. Operating Room José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 43

43

Step by Step Vitrectomy

xx Requirements 43

Ophthalmologic Surgery Table 43; Instrument Column 45; Integrated Vitrectomy Systems 45; Image Recorder 45; Operating Microscope 46

5.2. Visualization Systems

49

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 49 Upright Image Contact Lenses 50 Landers Biconcave Lens 50; Machemer Magnifying Lens 51; Peyman Wide-angle Lens 52; Machemer Plano-concave Lens 52; Tolentino Twenty Degree Prism Lens 52; Tolentino Thirty Degree Prism Lens 52; Woldoff Biconcave Prism Lens 52

Wide-Angle-Viewing Systems 52 Use of the Erect Indirect Binocular Ophthalmic System 56

Other Visualization Systems 58 Combined Procedures 61

5.3. Endoillumination Systems

65

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 65 External Systems 65 Internal Systems 65 Chandelier System 67

5.4. Infusion pressure Systems

71

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 71 Hydrostatic Pressure 71 Infusion Pump or Gas Forced Infusion 72 Pressure Control 75 Low Intraocular Pressure 75;

High Intraocular Pressure 75

5.5. Infusion Devices Systems

76

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Twenty-Gauge Incisions 76 Opening the Conjunctiva 76

Twenty-Gauge Transconjunctival Vitrectomy 78

5.6. Suction and Cutter Systems

79

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 79 Active Aspiration 79 Passive Aspiration 83 Vitrectomy Probes 84 Constellation Vision System 85;

Stellaris PC Vision Enhancement System 88

5.7. Diathermy

90

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 90

5.8. Retinopexy José Juan Martínez-Toldos, Cristian Fernández-Martínez

93

Contents

xxi Introduction 93 Laser Endophotocoagulation 93 Argon Laser 96; Diode Laser (810 nm) 96; Yellow Laser (577 nm) 97

Green Diode Laser (532 nm) 96;

5.9 phacoemulsification

99

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 99

5.10 Ultrasonic Fragmentation

102

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 102

5.11 Forceps and Scissors

104

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 104

5.12 Vitreous Substitutes: Manipulators of Tissues

109

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 109 Hyaluronic Acid 109 Perfluorocarbon Liquids 109

5.13 Vitreous Substitutes: Tamponades

113

José Juan Martínez-Toldos, Cristian Fernández-Martínez

Introduction 113 Intraocular Gases 113 Silicone Oil 115

Silicone Solvent 116;

Heavy Silicone Oil 117;

Densiron 119

6. Basic Vitrectomy

121

Cristian Fernández-Martínez, José Juan Martínez-Toldos

Check List 121 Positioning the Patient 122 Visualization Systems 122 Contact Systems 122;

Noncontact Systems 122

Conjunctival Incisions 123 Sclerotomy 124 Pupil Management 127 Phacoemulsification 128 Surgical Technique 128;

Special Cases 129

Removing The Vitreous Humor: Basic Concepts 129 Aspiration Systems 131 Active Aspiration 131;

Passive Aspiration 132

Peeling Membranes in Vitrectomy 132 Segmenting Membranes 134; Membranes 136

Delaminating Membranes 135;

Staining

Perfluorocarbon Liquids 140 Uses of Perfluorocarbon Liquids 141; Intraoperative Management of Perfluorocarbon Liquids 142; Potential Problems during the Use of Perfluorocarbon 146

Fluid-Air Exchange 146

Step by Step Vitrectomy

xxii Use of Gas in Vitrectomy 147 Nonexpanding Gas 147; Expanding Gas 148; Clinical Indications of Gases 148; Air–Gas Exchange 148; Postoperative Management of Patients Receiving Intraocular Gas 149

Silicone Oil in Vitrectomy 149 Injection of Silicone Oil 149; Emulsification of the Silicone Oil 150; Indications of Silicone Oil Tamponade 150; Inferior Peripheral Iridectomy 151; Removal of Silicone Oil 151

Closure After Surgery 152

7. pars plana Lensectomy

156

Carlos Mateo, Anniken Burés

Introduction 156 Surgical Technique 156 Advantages of Pars Plana Lensectomy 158 Pars Plana Lensectomy Indications 159

Vitreoretinal Proliferation 159; Perforating Ocular Trauma with or without Intraocular Foreign Body 160; Proliferative Diabetic Retinopathy 162

8. Basic Endoscopic Vitrectomy

164

Vicente J Chaqués-Alepuz, Enrique V López-Sánchez

Basic Equipment for Endoscopy 164 Technical Aspects: Visualization 166 Image Rotation 167; the Beginners 169

Image Artifacts 168;

Technical Tips for

Endoscopic Posterior Vitrectomy: Basic Concepts and Indications 170 Surgeon’s Position 170;

Image Size and Lighting 171;

Blurred Image 171

Complications of Vitreoretinal Surgery that can be Avoided by Endoscopy 171 Vitreous Incarceration 171;

Controlling Intraoperative Bleeding 172

Techniques and Maneuvers of Vitrectomy and Endoscopy 173

Vitrectomy 173; Membranectomy 174; Fluid-Air Exchange 174; Endophotocoagulation 174; Pars Plana Lensectomy 175 Capsulectomy 175; Introducing Silicone Oil 175; Introducing Perfluorocarbon Liquid 176; Diabetic Retinopathy and Endoscopic Vitrectomy 176; Vitreous Hemorrhage 177; Neovascularization of the Iris with Opacity of the Media 177; Retinal Detachment Surgery 177; Proliferative Vitreoretinopathy 178; Endoscopic Vitrectomy for Crystalline Lens Fragments Luxated in the Vitreous Cavity 180; Endoscopic Vitrectomy in Endophthalmitis 181

9.

Minimal Incision Vitrectomy Surgery: Twenty-Three, Twenty-Five and Twenty-Seven Gauge

184

José Juan Martínez-Toldos, Javier A. Montero-Moreno, José M Ruiz-Moreno, Félix Armadá-Maresca, Natalia Pastora-Salvador, Anna Grabowoska, María Granados-Fernandez, Beatriz Manzano Muñoz

9.1 Twenty-Three Gauge Vitrectomy José Juan Martínez-Toldos

Introduction 184 Incision Construction 185 Vitrectomy 186 Closing the Incision 187

184

Contents

xxiii Benefits of Twenty-Three Gauge Surgery 187 Complications 187

9.2 Twenty-Five Gauge Vitrectomy

189

Javier A Montero-Moreno, José M Ruiz-Moreno

Introduction 189 Benefits of Microincision Vitrectomy 192 Drawbacks of Microincision Vitrectomy 192 Complications 192 Future Perspectives 193

9.3 Twenty-Seven Gauge Vitrectomy

196

Armadá Maresca Félix, Natalia Pastora-Salvador, Anna Grabowoska, María Granados-Fernandez, Beatriz Manzano Muñoz

Introduction 196 Instrumentation 196 Indications 199

10. Vitrectomy in Anterior Segment Surgery Complications

202

José Juan Martínez-Toldos, Juan Carlos Elvira-Cruañes

Introduction 202 Ocular Perforation in Retrobulbar Anesthesia 202 Transconjunctival Sub-Tenon’s Anesthesia 203; Perforation 203; Treatment 204

Retrobulbar Hemorrhage Anterior Vitrectomy 205

Ocular

205

Vitrectomy Following Vitreous Loss 206

Retained Lens Fragments 209

Surgical Indications 211; Associating Surgery at the Time of Lens Dislocation 211; Surgical Technique 212

Intraocular Lens Dislocation 216

Surgical Technique 219; Late Intraocular Lens Dislocation with the Capsular Bag 222; Mechanisms 223; Prevention 223; Treatment 224

Endophthalmitis 225

Etiology 226; Treatment 227; Endophthalmitis 229

Vitrectomy 228; Late-Onset

11. Eye Trauma Vitrectomy

235

Joséfina Bañuelos Bañuelos, Patricia Martínez-García, Javier Orduña-Azcona, Ana Orive-Bañuelos

Introduction 235 Vitrectomy in Open Traumatisms 235

Clinical History and Initial Examination 235; Presurgical Considerations 236; Surgical Technique 237

Special Situations 240

Trauma and Dense Vitreous Hemorrhage 240; Trauma and Retinal Detachment 241; Trauma and Intraocular Foreign Body 241; Trauma and Endophthalmitis 244

Vitrectomy and Compliactions of the Ocular Trauma 246 Macular Hole 246; Ocular Hypotony and Bulb Phthisis 247

12. Basic Vitrectomy in Diabetic Retinopathy Jose Garcia-Arumi, Anna Boixadera, Laura Distefano, Vicente Martinez-Castillo, Miguel Angel Zapata

250

Step by Step Vitrectomy

xxiv Introduction 250

Surgical Approach 251

Vitrectomy for Diabetic Macular Edema 257

13. Macular Surgery

261

Amparo Navea, Elena Palacios, Carmen Desco, Jorge Mataix

Surgery on the Surface of the Macula 261 Preliminary Considerations 261 Interview with the Patient 262 Surgery Preparation 263 Technical Requirements 263; Human Requirements 263; Preparation 263; Surgeon Preparation 263

Patient

Vitrectomy 264 Specific Technical Points in Macular Hole 265

Surgery in the Subretinal Macular Space 267 Severe Submacular Hemorrhage Located into the Macular Area 267 Masive Subretinal Hemorrhage that also Affects the Macula 269 Subfoveal Perfluorocarbon Bubbles 270

14. Vitrectomy for Retinal Detachment with and without proliferative Vitreoretinipathy J Fernando Arevalo, Reinaldo A Garcia, Veronica Oria

Introduction 272 Combined Vitrectomy and Scleral Buckling 273 Scleral Buckling Technique 273;

Encircling Exoplants 275

Scleral Suture Technique 277 Primary Vitrectomy 277

Basic Operative Steps in Primary Vitrectomy 277

Intraocular Tamponade 283 Small-Gauge Pars Plana Vitrectomy 283

Sclerotomies with 23-Gauge Vitrectomy 284; Vitrectomy 284

Sclerotomies with 25-Gauge

New Considerations in Fluid Dynamics During Small-Gauge Vitrectomy 285 Increasing Safety 286; Wound Closure 286; Retinal Tears 287; Hypotony 288; Endophthalmitis 288

Vitrectomy for Retinal Detachment with Proliferative Vitreoretinopathy 288 Risk Factors for the Development of Proliferative Vitreoretinopathy 289 Diagnosis of Proliferative Vitreoretinopathy 290 Classification of Proliferative Vitreoretinopathy 290 Type 1 291; Type 2 293;

Type 3 293;

Type 4 293;

Type 5 295

Surgery for Proliferative Vitreoretinopathy 295

Timing of Surgery 295; Scleral Buckling in Proliferative Vitreoretinopathy 296; Lensectomy and Intraocular Lens 296

Vitrectomy for Proliferative Vitreoretinopathy 297

Removal of Posterior Epiretinal Proliferation 298; Removal of Anterior Epiretinal Proliferation 298; Removal of Subretinal Proliferation 298; Relaxing Retinotomies and Retinectomies 299; Creating a Chorioretinal Adhesion 302; Intraocular Tamponade 302; Removal of Silicone Oil 303; Reoperations for Recurrent Retinal Detachment from Proliferative Vitreoretinopathy 304

Adjunctive Treatment in Proliferative Vitreoretinopathy 304

272

Contents

xxv Giant Retinal Tears 305 Postoperative Complications 306 Summary 306

15. Current Indications of Antiangiogenics in Vitrectomy

313

Mauricio Maia, Fernando M Penha, J Fernando Arevalo

Antiangiogenics: Overview 313

Introduction: Vascular Endothelium Growth Factor 313; Role of Bevacizumab and Ranibizumab in the Angiogenesis Process 313

Intraoperative Bleeding During Pars Plana Vitrectomy In Proliferative Diabetic Retinopathy 315 Introduction 315;

Vitreoretinal Bleeding 315

Preoperative Procedures to Minimize the Possibility of Intraoperative bLeeding 316 Blood Pressure Control 316; Antiplatelet and Anticoagulants—Is it Necessary to Discontinue Them before Surgery? 316; Intravitreal Injection of Anti-VEGF Inhibitors in Proliferative Diabetic Retinopathy 317

Intravitreal Injection of Anti-Vegf Before Surgery in Proliferative Diabetic Retinopathy 317

Rationale 317; Intravitreal Bevacizumab Before Pars Plana Vitrectomy in Proliferative Diabetic Retinopathy 317; Intravitreal Ranibizumab before Pars Plana Vitrectomy in Proliferative Diabetic Retinopathy 319; Technique of Preoperative Intravitreal Anti-VEGF Injection 319; Care During Preoperative Intravitreal Anti-VEGF Injection Before Pars Plana Vitrectomy in Proliferative Diabetic Retinopathy 320 Conclusion of Intravitreal Injection of Anti-VEGF Before Proliferative Diabetic Retinopathy 320

Techniques of Intraoperative Posterior Segment Bleeding Control 320

Rising the Intraocular Pressure 321; Fluid-Air Exchange 322; Perfluorocarbon Liquids 323; Endodiathermy and Cauterization 323; Laser Photocoagulation 325; Combination of Techniques 326

16. Use of Sustained Drug Release Implants in Vitrectomized Eyes

331

Jose Maria Ruiz-Moreno, Javier A Montero

Introduction 331 Clinical Case 334

17. Enzymatic Vitrectomy

337

Patricia Udaondo, David Salom, Salvador Garcia-Delpech, Manuel Díaz-Llopis

Introduction 337 Concept of Enzymatic Vitrectomy 339 Methods and Mechanism of Action 339

18. posterior Vitrectomy Complications Carme Guardia, Jaume Catalá, Jairo Hoyos-Chacón

Introduction 343 Intraoperative Complications 343 Sclerotomy Complications 343

Visualization Problems 346 Retinal Tears 352;

Retinopexy Complications 354

Postoperative Complications 354

Corneal Complications 354; Ocular Hypertension and Glaucoma 355; Vitreous Hemorrhage 357; Retinal Detachment 358; Proliferative Vitreoretinopathy 359; Intraocular Inflammation and Fibrinoid Reaction 360; Tamponade and Manipulator Agents Complications 360; Endophthalmitis 364; Cataract 364

To Prevent Vitroretinal Surgery Complications 365

343

Introduction

Evidence that the eye could tolerate, practically, complete removal of the vitreous was provided in 1962, when Kasner1, 2 introduced the concept of open vitrectomy by removing the vitreous using a cellulose sponge and scissors. Almost a decade later in 1971, Machemer3-5 reported the first closed vitrectomy, conducted through the pars plana, using a multipurpose instrument capable of cutting, infusing and producing enough suction to grasp, cut, and extract the vitreous. With the introduction in 1972 of a fiber optics illumination system, the method was able to achieve the four basic functions of aspiration, cutting, infusion and endoillumination. The set up used by Machemer was later adapted by O’Malley and Heintz6 to separate the cutting and aspiration functions from endoillumination. Infusion was also separately achieved by a cannula sutured to the sclera, thus transforming the technique into a more precise and controllable bimanual procedure. Subsequent developments served to further improve these instruments to enable better control of suction power during vitrectomy. Among these developments, we should also mention endophotocoagulation systems, wideangle contact and noncontact visualization systems, intraocular pressure control pumps, substances for manipulating the retina (liquid perfluorocarbons) and gases or silicone oils used for tamponade; introduced using fluid injection pumps. The last two years have seen the introduction of vitrectomy machines showing improved flow control through the possibility of varying the duty cycle. The cutting speeds achieved using this system are some 5000–7000 cuts per minute and reports exist of even 10,000 cuts per minute. These developments add safety to the technique. For more than 10 years, 25-gauge instruments have been available that permit surgery through a 0.5 mm incision and avoid the need for any scleral or conjunctival sutures.7 For more complex cases, the 23-gauge instrument vitrectomy procedure, developed by Eckart, has been widely accepted and is today amongst the most frequently used systems by surgeons worldwide.8 Tano recently described a membrane peeling procedure based on the use of 27-gauge instruments and currently we have 27-gauge instruments available that allow a surgeon to conduct a complete vitrectomy in selective cases.9 Today’s therapeutic armamentarium has also been expanded by the introduction of dyes, to stain the epiretinal membranes and the internal limiting membranes, such as trypan blue, indocyanine green and brilliant blue, the later being the most notable.

Step by Step Vitrectomy

xxviii Finally, nonstaining agents aiming at improving a surgeon’s visualization of the vitreous and other membranes include the synthetic corticosteroid triamcinolone, whose crystals are deposited on these structures thus facilitating their removal. Other new medications worthy of mention are sustained drug delivery systems, such as dexamethasone or fluocinolone implants, that treat inflammatory diseases and macular edema. However, the greatest stars of all have been antiangiogenic or antivascular endothelium growth factor agents used initially to treat the wet form of age-related macular degeneration but that are today used to treat any vessel proliferation process, mainly diabetic retinopathy. Special mention should also be made of the use of enzymes, such as plasmin, to detach the posterior hyaloid, resolving certain macular problems. Research efforts in improving instrumentation and measurement devices continue to grow and so do the number of indications for surgery.10 This rapid pace has been set by the significant improvement in data communication so that changes produced can be transmitted to the scientific community on an almost daily basis. Continuing education programs have also forced the constant training of the vitreoretinal experts. Finally, we should also mention the emergence of new computer simulators, which are proving extremely useful for surgeons embarking on this technique.11,12

REFERENCES 1. Kasner D. Vitrectomy a new approach to the management of vitreous (Interview) Highlights Ophthalmol. 1969;11:304. 2. Kasner D, Miller GR, Taylor WH, et al. Surgical treatment of amyloidosis of the vitreous. Trans Am Acad Ophthalmol Otolaryngol. 1968;72(3):410-8. 3. Machemer R, Buettner H, Norton EW, et al. Vitrectomy: a pars plana approach. Trans Am Acad Ophthalmol Otolaryngol. 1971;75(4):813-20. 4. Machemer R, Parel JM, Buettner H. A new concept for vitreous surgery. I. Instrumentation. Am J Ophthalmol. 1972;73(1):1-7. 5. Machemer R. A new concept for vitreous surgery. 7. Two instrument techniques in pars plana vitrectomy. Arch Ophthalmol. 1974;92(5):407-12. 6. O’Malley C, Heintz RM. Vitrectomy with an alternative instrument system. Ann Ophthalmol. 1975;7(4):585-8, 591-4. 7. Fugii GY, De Juan E, Humayun MS, et al. A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology. 2002;109(10):1807-12. 8. Eckardt C. Transconjunctival sutureless 23-gauge vitrectomy. Retina. 2005;25(2):208-11. 9. Oshima Y, Wakabayashi T, Sato T, et al. A 27-gauge instrument system for transconjunctival sutureless microincision vitrectomy surgery. Ophthalmology. 2010;117(1):93-102. 10. Verma D, Wills D, Verma M. Virtual reality simulator for vitreoretinal surgery. Eye (Lond). 2003;17(1):71-3. 11. Hikichi T, Yoshida A, Igarashi S, et al. Vitreous surgery simulator. Arch Ophthalmol. 2000;118(12):1679-81. 12. Rossi JV, Verma D, Fujii GY, et al. Virtual vitreoretinal surgical simulator as a training tool. Retina. 2004;24(2):231-6.

chapter 1

Surgical Anatomy Cristian Fernández-Martínez, José Juan Martínez-Toldos

INTRODUCTION The anatomy of the ocular globe essentially determines the surgical approach to vitreoretinal diseases. Hence, a good knowledge of the different anatomical relations will help the vitreoretinal surgeons perform many of the maneuvers and procedures described in this book. In this chapter, we review the anatomical features that are most relevant for a vitrectomy.

ANATOMY OF THE VITREOUS The vitreous humor (4 ml by volume) occupies 80% of the ocular volume and is really a connective tissue, whose most important functions are to confer optical transparency to the larger globe cavity, to act as a nutrition source for the crystalline lens and probably to take part in the retinal metabolic processes. Its gel-like consistency is the result of its composition—98% water and 0.15% macromolecules such as hyaluronic acid, collagen and soluble proteins. The rest of the vitreous humor is made up of ions and low molecular weight solutes. Recently, the presence of other noncollagen soluble proteins has been described such as fibronectin, fibulin, opticin and VIT1, which likely plays a key role at the vitreoretinal interface.1, 2 Vitreous collagen is organized as fibrils comprised of collagen type II mostly but also of collagen types IX, V and XI. To form each vitreous fibril, these three collagen types need to be assembled. Collagen fibrils aggregate to form numerous fibers of greater diameter. These fibers are randomly distributed and interwoven to form a large collagen network or mesh, which constitutes the vitreous scaffold (Fig. 1).3 The density of these fibers varies among the different vitreous zones, being lower in the central vitreous zone, and greater in the anterior (zonule, posterior capsule of the crystalline lens) and posterior

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2 (adjacent to the retina) vitreous cortex. The region with the highest density of fibers is the vitreous base (anterior and posterior to the ora serrata).2, 3 This density gradient has important implications during vitrectomy since a great concentration of fibers will mean greater adhesion among these fibers and their greater attachment to the underlying retina, thus offering greater resistance to aspiration, with the consequent risk that the vitreotome will produce traction on the retina leading to its iatrogenic rupture. The anterior vitreous surface, or anterior hyaloid is inserted in the posterior capsule of the crystalline lens forming a circular zone 8–9 mm in diameter known as Wieger’s hyaloidocapsular ligament. This ligament constitutes the union between the anterior hyaloid and the anterior-most portion of the Cloquet’s canal, leaving a space between the two, called Berger’s space. The Cloquet’s canal is the embryonic remnant of the hyaloid artery, which runs from the optic nerve, where it originates in the shape of a funnel and creates the prepapillary space of Martegiani, and narrows as it passes through the central vitreous until it reaches the retrocrystalline lens zone as described above (Fig. 2).4

Vitreous Base and Vitreoretinal Interface The vitreous base accommodates the insertion of collagen fibers on both sides of the ora serrata along 360° of the ocular circumference. It is the region with

Figure 1  Meshwork of collagen fibers or filaments interspersed with large molecules of hyaluronic acid, which absorb large quantities of water to give the vitreous humor a gel-like consistency

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Figure 2  Anatomy of the vitreous humor

the highest concentration and density of vitreous fibers. Its most anterior edge occurs 2 mm in front of the ora in all four quadrants; its most posterior margin appears some 2–3 mm behind the ora in the temporal quadrants and at some 3–4 mm in the nasal quadrants. The vitreous base is contained within a 5–10 mm zone behind the limbus in the temporal quadrants and occurs 5–12 mm behind the limbus in the nasal quadrants.3,4 This needs to be taken into account specially when using a scleral indentation device whose main objective is to relax the base of the vitreous and bring it toward the underlying retina. The so-called vitreoretinal interface refers to the existing connections between vitreous cortex and underlying retina. The collagen fibers of the vitreous cortex run parallel to the inner surface of the retina across all but one region of the interface, the vitreous base. While at the rest of the interface, the stability of the vitreoretinal junction is attributed to chemical bonds between the collagen type II of the cortex and collagen type IV of the internal limiting membrane, at the vitreous base, the cortex fibers do not run parallel to the inner retina, rather they appear at right angles to it, directly inserting in the retinal tissue and intermixing with the basement membranes of the Müller cells without any apparent chemical bonds.2,3 This real anatomical binding explains why the vitreous base is surgically nonresectable and inseparable from the retina, even after severe eye trauma (Fig. 3). The most posterior vitreous is firmly attached to the adventitia of the retinal blood vessels, and to the margins of the optic nerve and macula. This firm posterior adhesion is responsible for the different vitreoretinal traction syndromes described in subsequent chapters.

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4

Figure 3  Diagram showing the arrangement of collagen fibers at the vitreous base. Note the direct contact between these collagen fibers and the Müller cell layer

ANATOMICAL DISTANCES IN VITRECTOMY Knowing the distances of the different anatomical structures relative to the limbus is essential for most vitrectomy procedures.

Crystalline Lens The crystalline lens, a biconvex structure located in the posterior chamber of the ocular globe, has a spherical power of 20D in an average adult. Since surgical access during vitrectomy is often conducted in the presence of the crystalline lens, it is important for the surgeon to be aware of its diameter. The equatorial diameter of the crystalline lens is 6.5 mm in newborns and 9–10 mm in adults, while its anteroposterior diameter is 3 mm at birth, increasing with age from the third decade of life to around 6 mm in elderly subjects.4,5 The crystalline lens should be avoided from the time the initial sclerotomies are placed until the end of surgery, since any slight damage will lead to its complete or partial opacification.

Extraocular Muscles The distance between the limbus and the anterior insertion of the four rectus muscles increases as follows: medial rectus (5.5 mm) → inferior rectus (6.5 mm) → lateral rectus (6.9 mm) → superior rectus (7.7 mm). The “spiral of Tillaux” is the name given to an imaginary line that passes in this order through the anterior insertion points of each rectus muscle and this line marks the position of the ora serrata with respect to the corneal limbus (Fig. 4)5.

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5

Figure 4  The spiral of Tillaux marks the position of the anterior insertions of the rectus muscles and ora serrata with respect to the corneal limbus

Ciliary Body The ciliary body is 6–7 mm long and is made up of two anatomically and functionally differentiated parts: pars plicata and pars plana. The pars plicata occupies some 2.5 mm posterior to its insertion at the scleral spur, is highly vascularized and formed by some 70 radial folds or ciliary processes, with a role in the production of aqueous humor and as an attachment structure for the zonule fibers of the lens. The pars plana extends some 3–4 mm from the pars plicata to the ora serrata. It is pigmented, completely smooth, relatively avascular and, as such, is the ideal zone for surgical access at some 3–4 mm from the corneal limbus6,7 (Figs 5 and 6). In children, the position of a sclerotomy needs to be corrected due to the different sizes of the ciliary body during eye development. Several morphometric studies6,8,9 have shown that the ciliary body grows from birth until 18 years of age. Based on these findings, different authors propose distances from the limbus for a sclerotomy in pediatric vitrectomy10 which are given in Table 1.

Blood Vessels In some surgical procedures, the extraocular muscles need to be manipulated and other procedures have to do with the blood vessels that supply these muscles. The muscular branches of the ophthalmic artery supply most of the extraocular muscles since they give rise to the anterior ciliary arteries. Each

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6

Figure 5  Position of the ciliary body in relation to the sclerocorneal limbus.

B

A

Figures 6A and B  (A) Inserting the microvitreoretinal blade 4 mm from the limbus; (B) Sclerotomy and its relation to the ora serrata and lens

Table 1 Distances from the limbus for a sclerotomy in pediatric vitrectomy Age group

Distance from limbus

1–6 months

1.5 mm

6–12 months

2 mm

1–2 years

2.5 mm

2–6 years

3 mm

6–18 years

3.5 mm

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7

Figure 7  Vortex veins and their anatomical relations

muscle contains 1–3 anterior ciliary arteries. During their journey toward the anterior pole, these arteries enter the globe’s episclera and irrigate the whole anterior segment. Maneuvers that compress, segment, or modify the anatomy of the extraocular muscles and sclera can compromise the arterial blood supply of the anterior segment.4,5 The venous system that runs parallel to the arterial network merits a special attention. In general, there are four vortex or vorticose veins located posteriorly to the equator (at some 14–18 mm from the limbus). These are usually observed close to the nasal and temporal margins of the inferior and superior rectus muscles.4,5 Their compression should be especially avoided during the circumferential placement of episcleral implants (Fig. 7).

REFERENCES 1. Bishop PN. Structural macromolecules and supramolecular organization of the vitreous gel. Prog Retin Eye Res. 2000;19(3):323-44. 2. Le Goff MM, Bishop PN. Adult vitreous structure and postnatal changes. Eye (Lond). 2008;22(10):1214-22. 3. Olsen BR. New insights into the function of collagens from genetic analysis. Curr Opin Cell Biol. 1995;7(5):720-7. 4. Spaide RF, Miller-Rivero NE. Anatomy. In: Spaide RF (Ed). Diseases of the Retina and Vitreous. Philadelphia: Saunders; 1999. 5. Greve MD. Vitreoretinal surgical anatomy. In: Peyman GA, Meffert S, Conway M, Chou F (Eds). Vitreoretinal Surgical Techniques. United Kingdom: Martin Dunitz; 2001. pp. 2-6.

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8 6. Bron AJ, Tripathi RC, Tripathi BJ (Eds). Wolff’s Anatomy of the Eye and Orbit, 8th edition. London: Chapman & Hall; 1997. 7. Hairston RJ, Maguire AM, Vitale S, et al. Morphometric analysis of pars plana development in humans. Retina 1997;17(2):135-8. 8. Streeten BW. Ciliary body. In: Duane TD, Jaeger EA (Eds). Biomedical Foundations of Ophthalmology. Philadelphia: Lippincott; 1995. 9. Aiello AL, Tran VT, Rao NA. Postnatal development of the ciliary body and pars plana. A morphometric study in childhood. Arch Ophthalmol. 1992;110(6):802-5. 10. Lemley CA, Han DP. An age-based method for planning sclerotomy placement during pediatric vitrectomy: a 12-year experience. Retina. 2007:27(7);974-7.

chapter 2

Presurgery Examination Manolo Baeza Diaz, José Juan Martínez-Toldos

MEDICAL HISTORY The medical history of the patient should be established, paying particular attention to the onset of symptoms, previous eye surgery and complications, current eye or systemic medication, possible allergies, and whether the patient is taking anticoagulants. The surgeon should clearly inform the patient of the possible risks and benefits of surgery, and the expected visual outcome of the procedure. The patient should also be informed about the possibility of needing more than one operation and the need to adopt a certain head position after surgery if the use of gas or silicone oil is planned.

VISUAL ACUITY Best corrected visual acuity should be determined for the patient and if possible should be confirmed by another clinician. The patient’s light perception and projection capacity should also be checked using light from the indirect ophthalmoscope in an opaque medium by asking the patient whether the light is on or off. Patients unable to perceive light should not undergo intraocular surgery.

Pupil Reflexes The patient should show normal pupil reflexes when tested even in the presence of markedly opaque media or dense vitreous hemorrhage. Loss of the pupil reflex generally indicates optic nerve damage but can also occur in severe cases of retinal detachment or a large macular lesion.

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Color Perception The results of this test are affected by the presence of blood. A positive result suggests the macula is not detached but negative results are inconclusive.

Vascular Entoptic Test A transilluminator light probe is applied to the closed eye with the patient looking downward. When the light source is removed, a patient with a normal retina should be able to see a negative image of the retinal blood vessels. A positive result suggests that posterior retina is not detached in 30°. However, some patients with a normal retina show a negative response to this test, diminishing its value.

Slit Lamp Microscopy This is used to check the transparency of ocular media such as the cornea and crystalline lens. Patients with cornea guttata and a low endothelial cell count have an increased risk of postsurgical edema. Epithelial erosions are common in diabetic patients. The need for crystalline lens surgery should be assessed. Subcapsular lens opacities interfere most with intraoperative visualization and are the opacities that most often progress following surgery, especially if gas is used. If the patient is phakic, biometry will in any case be needed to calculate the power of the intraocular lens, whether combined cataract/vitreous surgery is programmed or not, since the crystalline lens could be damaged and need to be extracted. In patients who have undergone previous cataract surgery, the type of intraocular lens present and its stability will need to be assessed especially if the use of intraocular gas or silicone is anticipated and if opacity of the posterior capsule or synechiae that could hinder mydriasis exists. In patients subjected to trabeculectomy, the filtration bleb will have to be avoided during surgical access for the vitrectomy. During surgery, muscle retroinsertion should be considered in case a scleral buckle needs to be used. Rubeosis iridis should be ruled out by examining the patient through the undilated eye with magnification. Rubeosis in a patient with vitreous hemorrhage requires an emergency vitrectomy and panretinal photocoagulation.

Tonometry Indentation tonometry is the most adequate procedure but in the case of an irregular cornea, it is easier to use the Tonopen (applanation tonometry). A low intraocular pressure does not cause phthisis bulbi; rather it is the phthisis that causes hypotony. Erythroclastic and closed-angle glaucoma should be ruled out (if a scleral buckle is to be used, the need for previous laser treatment will have to be evaluated).

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11

EXAMINING THE FUNDUS Indirect Ophthalmoscopy Compared to direct ophthalmoscopy, indirect ophthalmoscopy provides a better, more peripheral view of the retina, even when the ocular media is semi opaque. The procedure may be accompanied by scleral indentation, which allows the surgeon to reach the ora serrata. The image produced of the retina is steroscopic, inverted and for the examination a 20D or 28D lens is needed. The greater diopter this lens has the greater will be its angle of vision but the lower will be its magnification. These lenses also provide better vision when looking through small pupils and gas bubbles. The morphology of the retina is observed in such a way that if the detached retina is concave, this indicates a traction retinal detachment, while a convex detached retina would suggest rhegmatogenous retinal detachment. Indirect ophthalmoscopy also serves to detect a detached macula.

Biomicroscopy of the Retina Even using a 20D lens, the magnification power offered by the indirect fundoscope is insufficient to detect subtle retinal changes or vitreous modifications. This is best done with a retinal slit lamp through a Goldmann contact lens, Mainster lens, panfundoscopic lens or a noncontact 60D, 78D or 90D lens. These provide a more magnified image of the retina. Newer more specialized lenses also exist such as the SuperField, and in general lower powers offer greater magnification, better axial resolution and better stereoscopic vision accompanied nevertheless by a smaller field of view. Besides its use for examining the posterior pole, the Goldmann lens allows observation of the retinal periphery so that we can check for small tears that cannot be seen by indirect ophthalmoscopy. Retinal biomicroscopy allows the surgeon to check for epiretinal membranes, macular holes, macular edema, vitreous turbidity and floaters, traction epicenters of diabetic fibrovascular proliferations, vascular occlusions, neovascularizations, and the presence of neurosensory detachment. In summary, this procedure enables us to examine the retina with special reference to macular disease and the vitreous-retinal interface.

ULTRASONOGRAPHY The term ultrasound applies to all sound waves with a frequency greater than 20 kHz. When an ultrasound wave crosses a tissue, part of the wave is reflected back toward the probe. This reflected wave is known as an echo. Echos are produced by acoustic contact zones that form at the junction between the media, where different velocities of sound occur; the greater the difference between two media the greater will be the echo generated. The transducer at the tip of

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12 the probe emits ultrasound pulses and receives the reflected echos. The echos detected are processed in the instrument and represented on the screen in the form of a scan. The types of scans most frequently used are A-and B-scans. An A-scan is a unidimensional acoustic representation, in which echos appear as vertical spikes emerging from a baseline. The space between these peaks provides information on the measurements of ocular structures and the height of the peaks indicates the amplitude of the echo. A B-scan ultrasonography produces a two-dimensional acoustic cross section, whereby echos appear on the screen as points of different intensity. The coalescence of multiple points on the screen creates a two-dimensional cross section of the tissue being examined. The following characteristics of a tissue can be assessed: ƒƒ Reflectivity: this is given by the height of the wave peak in mode A. Depending on this height, brightness will change such that we can distinguish a more reflective lesion, such as a detached retina, from a detached posterior vitreous. ƒƒ The internal structure of a tissue: this gives an idea of the histological architecture of a lesion. Thus, a homogeneous image will show similar A-mode echos indicating a regular internal structure such as the structure of a tumor. ƒƒ The density of a tissue: as the ultrasound beam crosses a tissue the waves that appear on the A-scan produce less sound. If echos are greatly attenuated, this means a high tissue density and waves rapidly decrease. If we draw a line joining the different waves until the isoelectric line, this will give us an angle called the kappa angle, which is more marked the greater the attenuation is. In mode B, attenuation corresponds to the acoustic shadow, a vacuum of echos that occurs when a lesion is highly reflective such as in the case of a melanoma. ƒƒ Aftermovement: the patient is asked to move the eye and the echo is then recorded. This helps distinguish highly mobile lesions, such as detachment of the posterior vitreous, from those that are static such as a detached retina. An ultrasound examination would be indicated to detect and diagnose an ocular disorder in which a direct biomicroscopy examination is not possible or impaired by the opacity of the ocular media. Ultrasound is also used to diagnose and measure the size of a tumor. The ultrasonography should be conducted by the operating surgeon to gain as much information as possible before surgery. Below we describe the main findings we would expect in a vitreous, retinal or choroid disorder.

Vitreous Disorder In a healthy patient, the vitreous is very homogeneous. A B-scan will show an acoustically black space, and in an A-scan no echos are visible between the crystalline lens and retina. Possible findings are:

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13

Vitreous Hemorrhage The configuration of the vitreous and its density is revealed by peaks of different amplitude in the A-mode and spotting or an increase in density in the B mode. It should be checked if the retina is detached or in place and it will have to be distinguished from a detached posterior hyaloid. ƒƒ In a B-scan ultrasonography, posterior vitreous detachment appears as a fine undulating strand which may be completely separated from the retina or shows zones of adhesion in the papilla or in areas of retinal neovascularization. In an A-scan, echos are not usually high. The lesion’s aftermovement is generally mobile. ƒƒ Retinal detachment always appears as a more continuous, less mobile image. Often folds will be seen and when the detachment is total or extensive the detached retina always inserts in the optic disk and ora serrata. The subretinal space appears as an empty space. In mode A, retinal detachment appears as a peak of similar size as the scleral peak (Table 1). A detachment can be flat, bullous or funnel-shaped. Recent and bullous detachments may show a marked aftermovement, though less marked than a detached posterior vitreous. In contrast, long duration retinal detachments remain highly rigid.

Endophthalmitis The severity and extension of endophthalmitis can be assessed along with the presence of a foreign body or a detached retina. We may observe thickening of the retinochoroid layer and in advanced cases retinal detachment.

Table 1 Differential diagnosis of detachment of the posterior vitreous, retina or choroid Posterior vitreous

Retina

Choroid

Topography/ Structure /Characteristics

Smooth, open funnel-shaped; with or without insertion in papilla; inserted in ora

Smooth or folded, open or closed funnel-shaped; inserted in papilla and ora

Small, domed or flat; not inserted in papilla; insertion in ora or ciliary body

Quantitative

Peaks of variable amplitude < 100% in ora

Peaks of 100% even in ora

Spiky trace with wide double peaks; amplitude 100%

Aftermovement

Marked/moderate

Moderate/null

Mild/null

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Intraocular Foreign Body and Luxated or Subluxated Intraocular Lenses Ultrasonography enables us to better locate and quantify intraocular damage. In B-mode, a brilliant signal is produced with a shadow posterior to the foreign body. In A mode, high reflectivity peaks appear.

Proliferating Diabetic Retinopathy This condition produces a great variety of images such as vitreous hemorrhage, fibrovascular membranes or traction retinal detachment. The latter are usually located around the papilla or in vascular arcades (Fig. 1). Continuous traction at a given point leads to a tent-shape detachment; however, if affecting several points a hammock-shaped detachment is produced. When traction is more extensive the detachment is a table-top detachment and if there is a massive contraction of the vitreous a funnel-shaped detachment may occur.

Retinoschisis This condition generally affects the inferotemporal quadrants. A smooth membrane that does not affect the optic nerve disk can be seen; it is more focal, smooth and thinner than a detached retina.

Scleral Buckles Being dense materials, in mode A, these show a high internal reflectivity that generates an orbit shadow.

Figure 1  Retina appears as a highly reflective membrane protruding into the vitreous cavity with vitreous gel at its extreme ends

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15

Tumor Masses Ultrasonography is the most important diagnostic tool for intraocular tumors. According to the echogenic features of a lesion, we can differentially diagnose different tumors or other lesions such as neovascular membranes with subretinal hemorrhage. Through ultrasonography, we can also determine tumor size and its progression or remission. Hemorrhagic Choroid Detachment (expulsive hemorrhage) ƒƒ B-scan: elevated detached choroid of rounded appearance. Note the choroid space is opaque (coagulated blood). ƒƒ A-scan: double peak with low peaks in the choroid space (Figs 2 and 3). Through ultrasonographic imaging we can: ƒƒ determine the location and extension of a hemorrhage; ƒƒ examine the state of the retina and detect whether there is retinal detachment; ƒƒ distinguish between a hemorrhage or choroid effusion; and ƒƒ monitor the coagulate lysis process to decide upon the best moment for drainage surgery which is usually from 7 days to 14 days (Fig. 4).

Figure 2  Ultrasound image of hemorrhagic choroid detachment

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Figure 3  A detached choroid appears as highly echogenic convex lines in a B-scan

Figure 4  Progressive lysis of the coagulate in choroid hemorrhage

FLUORESCEIN ANGIOGRAPHY Fluorescein angiography offers information on blood flow through the retina, structural features of blood vessels and changes in the retinal pigment epithelium that affects its capacity to block the fluorescence of the dye or to allow the passage of fluorescein to the deeper layers of the retina. Fluorescein angiography can be used to diagnose a majority of retinal diseases although

Chapter 2    Presurgery Examination

17 with the advent of optical coherence tomography and other more precise imaging tools, the technique is rapidly being abandoned for the diagnosis and follow-up of many of these conditions especially at the macular level. For a surgical vitreoretinal indication, angiography is mostly used today to detect fibrovascular proliferations and traction retinal detachments produced as a consequence of vascular ischemia in diseases such as diabetic retinopathy, vascular occlusions or vasculitis. It is also useful to distinguish an exudative from a rhegmatogenous retinal detachment in which there is no tear in the retina or if one or more zones of exudation from the choroids to the subretinal space exist.

ELECTROPHYSIOLOGY Electroretinography This method uses electrodes to measure the response of the retina to stimulation using a light source of appropriate intensity. It is used to assess the functional integrity of the retina, specifically of the rods, cones, and both photoreceptor systems along with Müller and bipolar cells but it is not suitable for detecting abnormalities in ganglion cells and therefore the optic nerve.

Evoked Visual Potentials This technique records electric potentials produced in response to a standardized light stimulus and represents the combined response of the different visual cortex areas. It is used to assess macular function and the functional integrity of the visual pathway. It enables us to identify a dysfunction in the visual pathway and gives an idea of the extent of demyelination if potentials are delayed (latency increased) or the presence of impaired axon activation in the pathway (potentials reduced). Electrophysiological tests are especially useful to diagnose retinal degenerative diseases or for a differential diagnosis of macular disease, optic nerve disorders and mimicking symptoms. In diseases that induce opaque media such as vitreous hemorrhage, these tests serve to assess potential retinal function or possible optic nerve involvement.

Bibliography 1. American Academy of Ophthalmology. Retina y vítreo 2008-2009. Barcelona: Elsevier España. 2009. p. 424 (ISBN: 978-84-8086-359-9). 2. Chu TG, Green RL. Suprachoroidal hemorrhage. Surv Ophthalmol. 1999;43(6): 471-86. 3. Friberg TR. Examination of the retina: ophthalmoscopy and fundus biomicroscopy. In: Albert DM, Miller JW, Azar DT, Blodi BA (Eds). Albert

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18 Jackobiec’s Principles and Practice of Ophthalmology, 3rd edition. Philadelphia: W.B. Saunders. 2008. 4. Kanski J. Oftalmología Clínica, 6th edition. Barcelona: Elsevier España. 2009. p. 907 (ISBN: 978-84-8086-441-1). 5. Mascaró F, Mascaró F, Caminal JM. Atlas de ecografía ocular. Barcelona: Editorial Glosa SL. 2007. p. 94 (ISBN: 978-84-7429-360-9). 6. Ryan SJ. Retina. Enfermedades hereditarias y retina, 4a edition. Madrid: MARBAN libros SL. 2009. p. 789 (ISBN: TD: 978-84-7101-616-4).

chapter 3

Vitrectomy and Optical Coherence Tomography David Salom, Patricia Udaondo, Manuel Díaz Llopis, José Juan Martínez-Toldos

INTRODUCTION The optical coherence tomography (OCT) is a diagnostic technique that generates transversal cuts (tomographies) off the retina with a resolution, which allows differentiation of the retinal and subretinal histological structures. This is achieved with an optical measurement technique called “low coherence interferometry”, similar to that used in B echography but instead of using ultrasounds this technique uses a beam of light with an 830 nm wavelength, optimal for visualization of the retina. The first commercially available OCT machine was the Stratus OCT launched in 1995 by Carl Zeiss Meditec (Dublin, California). To generate the images of the retina, the Stratus OCT used a technology called “time domain OCT” (TD-OCT) with an axial resolution of 10 mm and with a speed of 400 A-scans per second. The TD-OCT allowed, for the first time, the visualization of histological cuts off the retina in vivo. During the last years a new technology has been developed for obtaining the retinal images, called “spectral domain OCT” (SD-OCT) that eliminates the necessity of the reference mirror movement, mandatory in the TD-OCT. The SD-OCT machines can obtain images of the retina with an axial resolution of 5 mm and a speed of 20,000 A-scans per second. This technology has enabled, for the first time, not only to better distinguish histological retinal structures but also to generate tridimensional reconstructions of complete areas of the macula and the optic nerve. The SD-OCT made possible the reporting of many anatomical alterations in a great variety of retinal pathologies, the early detection of glaucomatous damage progression1 and visualization of histological alterations of everyday more anterior segment pathologies.2 Today, OCT is considered an essential clinical tool for the diagnosis and evaluation of therapeutic response in numerous ophthalmological pathologies.

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20 More than explaining the role of OCT developed in medical retinal pathologies; in this chapter we will concentrate on surgical retinal pathologies in which the OCT is essential in the diagnostic process and surgical planning. We will also increase our knowledge in the postoperative healing process and in the everyday nearest possibility of the intraoperative OCT.

OPTICAL COHERENCE TOMOGRAPHY IN MACULAR HOLES The OCT has become the gold standard for the preoperative identification of macular holes (MH) and is particularly useful in the differentiation between complete MH and lamellar or pseudoholes,3 as shown in Figures 1 and 2. In the postoperative analysis of the MH, the OCT has established parameters for better prognosis, specifically, those patients with higher retinal thickness at the borders of the hole had a better visual prognosis after the surgery, indicating that the MH with thin borders were less likely to close after the surgery.4 Another predictive factor for the visual restoration and surgical success in the MH was the distance between the hole margins measured by OCT. The prognosis was better in those holes with less distance between the margins, it was observed in the same study that the duration of the visual symptoms did not correlate with the diameter of the MH, proposing that the time of evolution of the MH

Figure 1  Complete macular hole associated to an epiretinal membrane

Figure 2  Lamellar macular hole associated an epiretinal membrane

Chapter 3    Vitrectomy and Optical Coherence Tomography

21 was not so determinant in the surgical success as it is the distance between the margins.5 Other authors had combined these two factors, establishing the macular hole index (MHI) easily calculated from the ratio between the heights of the MH borders and its diameter, if the MHI is greater than or equal to 0.5 the visual prognosis after the surgery is better.6 In the postoperative convalescence, the OCT has allowed us to monitor the closing procedure of the MH. It was observed that the MH close during the first month after the surgery and that the holes persisting for more than one month were more likely to never close.7 A fundamental parameter for being able to predict good visual results, in the early postoperative period after MH surgery, is the visualization at the fovea of normal external limiting membrane, because this fact can predict an adequate restoration of the photoreceptor layer.8 The OCT has also been able to show that the facedown position after the MH surgery was only useful in those MH with a diameter greater than 400 mm.9 On the other hand, OCT has allowed establish that the presence of subretinal fluid at the MH margins is a good predictive factor of successful closing of the hole after a first surgical failure. The hole dimensions, the type of tamponade, the duration of MH after the first surgery or the preoperative visual acuity did not correlate with the anatomic result after the reintervention.10

OPTICAL COHERENCE TOMOGRAPHY IN EPIRETINAL MEMBRANES Optical coherence tomography is a diagnostic tool more sensitive than the clinical evaluation when diagnosing epiretinal membranes (ERM).11 It has also allowed demonstrate the presence of a thickening of all the retinal layers in cases with idiopathic ERM; the internal nuclear layer (INL) is the one that has the highest degree of enlargement. The OCT has demonstrated that the INL is the retinal layer that contributes the most to changes in visual acuity in patients with ERM.12 If an INL thickness map is performed in patients with ERM, the areas with higher thickening correlates with the metamorphopsia areas of these patients; therefore the OCT could be considered an objective method to determine the localization of the metamorphopsias.13 In ERM and in vitreomacular traction syndrome (VTS), OCT is characteristic of the presence of a high reflectivity area between the junction line of the inner and outer segments (IS/OS) of the photoreceptors, and the line of the external segment of the cones at the center of the fovea by its round shape, has been named “cotton ball sign” and reflects the presence of an inward traction over the fovea. It can also be considered a good predictor of visual disturbances in the short term.14 In Figure 3, can be seen, an example of the cotton ball sign. These are clear examples of how the better resolution of SD-OCT is allowing us to better understand the functional alterations that are suffered by our patients. The OCT has given the surgeons a possibility to establish histological correlations with functional alterations, determining new times for

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22

Figure 3  Epiretinal membranes with the subfoveal cotton ball sign represented by a high reflectivity area between the junction line of the internal and external segments of the photoreceptors and the line of the external segment of the cones

surgery and even contraindicating procedures because of the low possibility of functional visual restoration after surgery. The OCT has also been able to establish predictive factors of the possible difficulty when peeling an ERM. The extension of adhesions and the presence of fibrillar changes determined by SD-OCT tridimensional reconstructions are a reliable preoperative assessment for the surgical removal of the ERM.15 In Figure 4, we can observe the spatial distribution of an ERM with a tridimensional reconstruction. With this general vision of how the ERM is affecting the retina, it is easier to localize areas of detachment that could be used to establish a correct surgical removal strategy of the ERM. In Figure 5 we can observe a much attached ERM to the retinal surface, representing a higher difficulty when performing the surgical procedure. Other than the preoperative visual acuity, the tomographic findings that determine better visual results after the surgical removal of an ERM are: the presence of normal IS/OS line, a smooth internal limiting membrane (ILM) profile, and the restoration of the normal foveal shape three months before surgery.16 These findings explain why there are patients with an unsatisfactory final visual acuity with a complete anatomic recuperation.

OPTICAL COHERENCE TOMOGRAPHY IN VITREORETINAL TRACTION SYNDROME Without any doubt, VTS is one of the pathologies in which OCT has become an indispensable tool for its diagnosis and postoperative evaluation. OCT is more sensitive than biomicroscopy in the detection of VTS that could benefit from surgery.17 The posterior hyaloid is represented by a thin line of middle reflectivity, opposed to ERM that is represented by a thicker, high reflectivity line with more evident attachments to the retinal surface as shown in Figure 6.

Chapter 3    Vitrectomy and Optical Coherence Tomography

23

Figure 4  Tridimensional reconstruction of an epiretinal membrane

Figure 5  Epiretinal membrane well attached to the retinal surface

Figure 6  Posterior hyaloid over an epiretinal membrane

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24 The OCT is useful in establishing the tridimensional configuration of the vitreomacular attachments to the posterior pole, playing an important role in the planning of the best way to access the subhyaloid space during vitrectomy.18 Thanks to the SD-OCT, it has been able to define two distinct patterns of the vitreous traction over the retina in patients with VTS. The first is represented by an incomplete posterior vitreous detachment in a “V” shape associated to the detachment of the fovea (Fig. 7). In these cases the surgical prognosis is favorable. The second is represented by a partial temporal posterior vitreous detachment associated to a prominent cystoid macular edema (Fig. 8). In these cases, a greater incidence of MH or macular atrophies have been observed after the surgery.19 A particular situation is the diffuse diabetic macular edema (DME), characterized by generalized areas of leakage in the central macula in which pathogenesis is not that well known. The treatment with grid laser photocoagulation or with intravitreal drugs administration is the only temporarily efficacy in many cases.20,21 Ophir et al described an important series of patients with diffuse DME in which only 24% did not have any associated signs of vitreomacular traction or ERM.22 A tridimensional reconstruction showing how the posterior hyaloid is attached to the retinal surface of a patient with diffuse DME is shown in Figure 9.

Figure 7  Vitreomacular traction syndrome in “V” shape

Figure 8  Temporal vitreomacular traction syndrome associated to a cystoid macular edema

Chapter 3    Vitrectomy and Optical Coherence Tomography

25

Figure 9  This picture shows, in a tridimensional reconstruction, the attachment of the posterior hyaloids to the inner surface of the retina in a patient with a diffuse diabetic macular edema

INTRAOPERATIVE Without any doubt, OCT has revolutionized the ophthalmology consultation generating important surgical changes in the patients with macular pathologies. The logical evolution of the OCT is to get incorporated in the surgical procedure itself. At this moment it is commercially available as a portable SD-OCT (Bioptigen, Inc., Research Triangle Park, NC, USA) that obtains images of the retina with the patient in supine position, as it happens with echography. The first clinical application of this device was in pediatric patients with good results.23 There are several publications of its intraoperative use in patients with MH, ERM and VTS. Images of the retina were obtained before and immediately after the vitrectomy or ILM, allowing the surgeon the correct result of the surgery before closing the eye.24,25 The portable Bioptigen OCT has also been used in complex retinal detachment surgeries, showing the presence of subfoveal fluid at the end of the surgery which is invisible through the surgical microscope.26 The weakness of this device is the necessity of stopping the surgical procedure in order to obtain the images, limiting the intraoperative applicability of this technology. Actually there are efforts trying to incorporate the OCT to the surgical microscope and creating “microscope-mounted OCT” (MM-OCT).27 The MM-OCT can obtain images of the retina simultaneously with the surgery; this technology has a clear practical applicability because it can give useful information to the surgeon in real time. The MM-OCT can obviously revolutionize the vitreoretinal surgery in the years ahead.

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26

REFERENCES 1. Schuman JS, Hee MR, Arya AV, et al. Optical coherence tomography: a new tool for glaucoma diagnosis. Curr Opin Ophthalmol. 1995;6(2):89-95. 2. Hoerauf H, Gordes RS, Scholz C, et al. First experimental and clinical results with transscleral optical coherence tomography. Ophthalmic Surg Lasers. 2000;31(3):218-22. 3. Hee MR, Puliafito CA, Wong C, et al. Optical coherence tomography of macular holes. Ophthalmology. 1995;102(5):748-56. 4. Hirneiss C, Neubauer AS, Gass CA, et al. Visual quality of life after macular hole surgery: outcome and predictive factors. Br J Ophthalmol. 2007;91(4):481-4. 5. Ullrich S, Haritoglou C, Gass CA, et al. Macular hole size as a prognostic factor in macular hole surgery. Br J Ophthalmol. 2002;86(4):390-3. 6. Kusuhara S, Teraoka Escaño MF, Fujii S, et al. Prediction of postoperative visual outcome based on hole configuration by optical coherence tomography in eyes with idiopathic macular holes. Am J Ophthalmol. 2004;138(5):709-16. 7. Jumper JM, Gallemore RP, McCuen BW, et al. Features of macular hole closure in the early postoperative period using optical coherence tomography. Retina. 2000;20(3):232-7. 8. Wakabayashi T, Fujiwara M, Sakaguchi H, et al. Foveal microstructure and visual acuity in surgically closed macular holes: spectral-domain optical coherence tomographic analysis. Ophthalmology. 2010;117(9):1815-24. 9. Solebo AL, Lange CA, Bunce C, et al. Facedown positioning or posturing after macular hole surgery. Cochrane Database Syst Rev. 2011;12:CD008228. 10. Hillenkamp J, Kraus J, Framme C, et al. Retreatment of fullthickness macular hole: predictive value of optical coherence tomography. Br J Ophthalmol. 2007;91(11):1445-9. 11. Do DV, Cho M, Nguyen QD, et al. Impact of optical coherence tomography on surgical decision making for epiretinal membranes and vitreomacular traction. Retina. 2007;27(5):552-6. 12. Koo HC, Rhim WI, Lee EK. Morphologic and functional association of retinal layers beneath the epiretinal membrane with spectral-domain optical coherence tomography in eyes without photoreceptor abnormality. Graefes Arch Clin Exp Ophthalmol. 2012;250(4):491-8. 13. Watanabe A, Arimoto S, Nishi O. Correlation between metamorphopsia and epiretinal membrane optical coherence tomography findings. Ophthalmology. 2009;116(9):1788-93. 14. Tsunoda K, Watanabe K, Akiyama K, et al. Highly reflective foveal region in optical coherence tomography in eyes with vitreomacular traction or epiretinal membrane. Ophthalmology. 2012;119(3):581-7. 15. Kim JS, Chhablani J, Chan CK, et al. Retinal adherence and fibrillary surface changes correlate with surgical difficulty of epiretinal membrane removal. Am J Ophthalmol. 2011;153(4):692-7. 16. Falkner-Radler CI, Glittenberg C, Hagen S, et al. Spectral-domain optical coherence tomography for monitoring epiretinal membrane surgery. Ophthalmology. 2010;117(4):798-805. 17. Gallemore RP, Jumper JM, McCuen BW, et al. Diagnosis of vitreoretinal adhesions in macular disease with optical coherence tomography. Retina. 2000;20(2):115-20.

Chapter 3    Vitrectomy and Optical Coherence Tomography

27 18. Chung EJ, Lew YJ, Lee H, et al. OCT-guided hyaloid release for vitreomacular traction syndrome. Korean J Ophthalmol. 2008;22(3):169-73. 19. Yamada N, Kishi S. Tomographic features and surgical outcomes of vitreomacular traction syndrome. Am J Ophthalmol. 2005;139(1):112-7. 20. Focal photocoagulation treatment of diabetic macular edema. Relationship of treatment effect to fluorescein angiographic and other retinal characteristics at baseline: ETDRS report no. 19. Early Treatment Diabetic Retinopathy Study Research Group. Arch Ophthalmol. 1995;113(9):1144-55. 21. Shimura M, Nakazawa T, Yasuda K, et al. Comparative therapy evaluation of intravitreal bevacizumab and triamcinolone acetonide on persistent diffuse diabetic macular edema. Am J Ophthalmol. 2008;145(5):854-61. 22. Ophir A, Martinez MR, Mosqueda P, et al. Vitreous traction and epiretinal membranes in diabetic macular oedema using spectral-domain optical coherence tomography. Eye (Lond). 2010;24(10):1545-53. 23. Muni RH, Kohly RP, Charonis AC, et al. Retinoschisis detected with handheld spectral-domain optical coherence tomography in neonates with advanced retinopathy of prematurity. Arch Ophthalmol. 2010;128(1):57-62. 24. Dayani PN, Maldonado R, Farsiu S, et al. Intraoperative use of handheld spectral domain optical coherence tomography imaging in macular surgery. Retina. 2009;29(10):1457-68. 25. Wykoff CC, Berrocal AM, Schefler AC, et al. Intraoperative OCT of a full-thickness macular hole before and after internal limiting membrane peeling. Ophthalmic Surg Lasers Imaging. 2010;41(1):7-11. 26. Lee LB, Srivastava SK. Intraoperative spectral-domain optical coherence tomography during complex retinal detachment repair. Ophthalmic Surg Lasers Imaging. 2011;42 Online:e71-4. 27. Ehlers JP, Tao YK, Farsiu S, et al. Integration of a spectral-domain optical coherence tomography system into a surgical microscope for intraoperative imaging. Invest Ophthalmol Vis Sci. 2011;52(6):3153-9.

chapter 4

Anesthesia Manuel Baeza, José Juan Martínez-Toldos

INTRODUCTION During surgery, handling the iris, ciliary body and sclera can be painful, and heat stimulation can also be uncomfortable. In addition, cryotherapy is known to be very painful, more so than the laser or cauterization. Thus, it is important that the patient is given the most appropriate form of anesthesia.1 The form of anesthesia to use in patients under anticoagulant/antiaggregant treatment is a controversial topic. For cataract surgery, this type of treatment need not be suspended. However, the risk of hemorrhage during vitreoretinal surgery dictates that anticoagulant treatment should be interrupted. The disease requiring anticoagulation treatment and the patient’s risk of thromboembolism should be known, since sometimes withdrawing an antiaggregant puts a patient at great unnecessary risk. Thus, a valve disease or stroke with arrhythmia and history of embolism is not the same as a stroke or myocardial infarction without cardiac arrhythmia. Also, the antiaggregant used should be known since not all show the same risk of inducing hemorrhage nor require the same duration of replacement therapy (Table 1). The reason for surgery is also important; for instance, a technique in which scleral bands are needed is associated with a greater risk of hemorrhage than a macular surgery procedure. The surgeon should assess the least invasive anesthesia method and select the replacement anticoagulant/antiaggregant with sufficient time before surgery. Also, a blood test will be needed to determine the international normalized ratio (INR), which should be within the recommended limits for the disease under anticoagulation therapy.1,2 The latest published recommendations propose personalized treatment prescribed by the patient’s internist and anesthetist. The current trend is to try

Chapter 4   Anesthesia

29 Table 1 Characteristics of some of the antiaggregants used for vitreoretinal surgery Antiaggregant

Mechanism

Safety margin for suspension

Risks

Aspirin, Adiro, AAS

Inhibits thromboxane A2 synthesis

7 days

-

Dipyridamole, Persantine

Inhibits phosphodiesterase

24 hours

-

Triflusal, Disgren

Inhibits cyclooxygenase

7 days

-

Ticlopidine, Ticlid

Blocks ADP receptor

10 days

Severe risk of hemorrhage

Clopidogrel, Iscover, Plavix

Blocks ADP receptor

7 days

Severe risk of hemorrhage

Abbreviations: AAS: Acetylsalicylic acid; ADP: Adenosine diphosphate

not to suspend antiaggregant and/or anticoagulant treatment by assessing the risk/benefits in each case.3,4 A recommended strategy would be: ƒƒ Patients with low emboligenic risk: suspend antiaggregant treatment ƒƒ Patients with high emboligenic risk: replace anticoagulants with lowmolecular-weight heparin treatment 3–5 days before surgery ƒƒ Patients with a very high emboligenic risk: assess the risks of maintaining treatment or replace antiaggregant with one of lower hemorrhage risk (e.g. Adiro 100 mg) besides the use of sub-Tenon’s or subconjunctival anesthesia and an atraumatic surgical technique.

TYPES OF ANESTHESIA The anesthesia options available are: ƒƒ General ƒƒ Topical: not recommended for vitreoretinal surgery ƒƒ Retrobulbar ƒƒ Peribulbar ƒƒ Sub-Tenon’s ƒƒ Subconjunctival: Introduced through sclerotomies in quick posterior pole procedures.

General Anesthesia The benefits of general anesthesia over local anesthesia are: noncooperative patients can be controlled and intraocular pressure can be reduced if needed;

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30 either by reducing CO2 through hyperventilation or reducing arterial pressure. General anesthesia may also help in controlling intraoperative hemorrhage by lowering arterial blood pressure. It is indicated in children, poorly cooperative patients because of phobias, hyperkinesia or mental impairment, in patients with a neurological disease (Parkinson’s or cerebral palsy) that prevents them from remaining still during surgery or subjects with tics or tremors. The use of a general anesthetic is also recommended in deaf patients, in perforating trauma patients and when surgery duration of more than 2–3 hours is anticipated. It should be noted that when a general anesthetic mixture containing nitrous oxide is used; its administration should be interrupted 10 minutes before injecting SF6 or C3F8 into the globe, to avoid the gas bubble rapidly expanding due to the entry of nitrous oxide from adjacent tissues because of the partial pressure gradient generated. This could cause a considerable intraocular pressure rise.5-7 With general anesthesia, the risk of oculocardiac reflex (OCR) is increased. However, OCR is usually transient since repeated stimuli will block the response. Generally, OCR will spontaneously stop a few seconds after the stimulus ceases. If OCR occurs, the maneuver triggering the reflex will have to be interrupted. This is usually muscle traction. In the case of a continued OCR, 0.5–1 ml of atropine should be given. In children, atropine is sometimes prophylactically administered. The medications mostly used for sedation to accompany both, a local and general anesthetic are: ƒƒ Anxiolytic agents –– Diazepam (Valium): has the drawback that active metabolites are released at the time it is administered. –– Midazolam: onset: 30–60 seconds; half-life: 3 hours; dose: 0.1–0.2 mg/ kg (anxiolytic of choice, anxiolysis, hypnosis, amnesia) ƒƒ Opioids –– Fentanyl: onset: 5 minutes; duration: 30–45 minutes; dose: 0.025–0.05 mg (analgesic of choice) ƒƒ Hypnotic agents –– Propofol: onset: 30–45 seconds; half-life: 2.5 minutes; dose: 1–2.5 mg/ kg (immediate hypnotic effect, lowers arterial and intraocular pressure, antiemetic). The agents mostly used prior to local anesthesia, to achieve adequate hypnosis and amnesia at the time of administration, are propofol or midazolam.8-10

Local Anesthesia The advantage of local anesthesia is that the patient can communicate and collaborate with the surgeon, along with 4–6 hours of pain relief following

Chapter 4   Anesthesia

31 Table 2 Most commonly used local anesthetics Drug

Concentration

Onset

Duration

Vascular effects

Lidocaine

0.5–4 mg/kg

Rapid (2–3 minutes)

1–2 hours

Vasodilation

Mepivacaine

0.5–2 mg/kg

Rapid (2–3 minutes)

1.5–3 hours

No

Bupivacaine

0.5–0.75 mg/kg

Slow (10 minutes)

3–8 hours

No

Ropivacaine

1 mg/kg

Medium (6–7 minutes)

3–8 hours

Vasoconstriction

surgery. Moreover, local anesthesia avoids the systemic complications of general anesthesia as well as coughs or vomiting, which sometimes occur after extubation. These could provoke hemorrhages or suture dehiscence. In addition, the use of a local anesthetic will eliminate the risk of OCR, avoiding hospitalization and the cost this entails. The most commonly used local anesthetics can be classified into two categories that are presented in Table 2. In one category, there are lidocaine and mepivacaine, which are rapidly acting (2–3 minutes) but have a short-lived effect, approximately 2 hours. In the other group, bupivacaine and ropivacaine have a slow onset of action; some 10 minutes, but a more prolonged effect of 6–8 hours. The ideal is, thus, to combine one from each group to achieve the benefits of both. Local anesthetics are usually given with hyaluronidase, an enzyme that hydrolyses glucosamine-glucuronic acid bonds, to improve their diffusion, achieve a more rapid effect, lower intraocular pressure and reduce proptosis. In contrast to hyaluronidase, adrenaline does not improve the efficacy or prolong the duration of a local anesthetic. A Honan balloon is also recommended to increase diffusion and reduce intraocular pressure and chemosis (Fig. 1).

Anatomy Applied to Anesthesia For the sensory innervation of the eye, signals are transmitted via the first branch of the trigeminal nerve, the optic nerve, which is in turn divided into three branches, of which the nasociliary branch comprises the innervation of the cornea, iris, ciliary body and sclera. The nasociliary nerve divides into one branch, which passes through the ciliary ganglion from where the short ciliary nerves emerge and other branches that accompany the optic nerve, the long ciliary nerves.11,12 In theory, we can divide the orbit into two compartments, intracone and extracone, bounded by the four rectus muscles that run from the annulus of

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32

Figure 1  Patient with a Honan balloon after injection of the anesthetic

Zinn, at the orbit’s apex, to the Tenon’s capsule at the ocular globe. The space between the rectus muscles contains connective tissue and fat but there is no defined intermuscular septum to isolate the two compartments (Fig. 2). Thus, any anesthetic introduced in the extracone space for peribulbar anesthesia can diffuse to the intracone space.13 We should remind ourselves of some of the measurements between the structures of the orbit. Thus, the mean distance from the apex to the inferior margin of the orbit is 48 mm (42–54 mm), the distance to the optic nerve from the inferior orbital edge is 33 mm and the ciliary ganglion occurs 10 mm from the apex.14

Figure 2  Orbit anatomy

Chapter 4   Anesthesia

33 The central retinal artery penetrates the optic nerve close to the ciliary ganglion. Its long intraorbitary course is susceptible to damage by puncture. In the inferior half of the orbit are the ophthalmic vein, ciliary ganglion and cranial nerve pairs, while through the superior and posterior zones run the ciliary arteries. For this reason, anesthesia at the inferior level is of greatest interest since this will block sensory-motor nerves and even signals transmitted along the optic nerve with a lower risk.12

Retrobulbar Block This mode of anesthesia consists of the intracone injection of the anesthetic targeted at achieving akinesia through blockage of the cranial nerve pairs and achieving anesthesia through blockage of the ciliary nerves by actions on the ciliary ganglion. Sympathetic and parasympathetic stimuli are also blocked, inducing intraocular pressure lowering and pupil dilation. The technique was first described by Knapp15 and was then popularized by Atkinson.16

Technique ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

Patient in a supine position looking straight ahead Retrobulbar 25 gauge needle, maximum length 35 mm Transconjunctival or transpalpebral approach Single point of access For a transpalpebral approach, the needle is slowly introduced through the lower eyelid at the junction of the middle third and outer third of the lower orbital rim (Fig. 3) passing through the orbital septum, and its direction changed by 25° as the equator of the eye is passed and then advanced into the muscular cone.

Figure 3  Initiating the transpalpebral retrobulbar injection process at the junction between the middle and outer thirds of the orbital rim

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34 ƒƒ The transconjunctival technique involves:

–– Introducing the needle (30 mm maximum length) with the slanted tip facing upward –– Aspiration and injection of 3–5 ml –– Subdermal injection. Honan balloon If we wish to achieve complete akinesia, it is sometimes useful to perform an infiltration at the inner third of the superior orbital rim given the superior oblique muscle is located in the extracone area. For akinesia of the orbicular muscle, an inferotemporal subdermal infiltration may be conducted before withdrawing the needle, or the facial muscle may be specifically blocked, using the Van Lint technique whereby infiltration is performed at the outer orbital rim, and extended inferiorly and exteriorly. Several complications of this technique have been described17,18 such as retrobulbar hemorrhage,19,20 puncture of the globe,21-23 optic nerve trauma or puncture, 24 subarachnoid injection causing central nervous system depression,25,26 ptosis and strabismus.27,28 Each of these complications and the preventive measures are described below. ƒƒ Retrobulbar hemorrhage –– Induces proptosis with or without subconjunctival hemorrhage, restricted extrinsic ocular motility and increased intraocular pressure. –– Incidence: 0.1–1.7% –– It can be resolved by applying pressure with the Honan balloon, although sometimes surgery needs to be rescheduled and rarely a lateral canthotomy is needed if central retinal ischemia occurs. ƒƒ Increased intraocular pressure –– Secondary to a retrobulbar hemorrhage or excess anesthetic –– Apply pressure with the Honan balloon ƒƒ Optic nerve damage –– It can lead to optical atrophy –– Needle may cause damage to the optic nerve or arteries or compress the optic canal –– Prevention: -- The patient should adopt a primary viewing position so that the optic nerve is further from the inferior muscles.29 -- Do not advance the needle more than 31 mm. ƒƒ Ocular perforation is a serious complication of retrobulbar anesthesia that needs to be prevented. A useful strategy is to move the needle sideways before injecting the anesthetic, to make sure this movement is not accompanied by the globe. –– It occurs more frequently in an elongated eye in myopic patients or when scleral bands are used. –– If the anesthetic is injected inside the globe, an abrupt intraocular pressure increase may be produced causing irreversible damage. In this case an anterior chamber paracentesis would have to be performed.

Chapter 4   Anesthesia

35 –– Puncturing the globe could cause a vitreous hemorrhage or retinal detachment, which would determine the need for vitrectomy and endophotocoagulation rather than puncture. Sometimes, retinal incarcerations dictate the need for a retinotomy. ƒƒ Subarachnoid diffusion of the anesthetic –– May lead to convulsions and respiratory arrest –– Passage of local anesthetic to central nervous system (CNS) –– A 2–3 hours support treatment is needed with intubation of the patient ƒƒ Muscular complications –– Ptosis and strabismus –– Due to the effects on the inferior rectus and most often the inferior oblique. Frequently due to toxicity of the anesthetic or trauma to the muscle. Less commonly due to cranial nerve pair damage.

Peribulbar Anesthesia Peribulbar anesthesia was described by Davis and Mandel30 and modified by Bloomberg.31 It consists of injecting the anesthetic into the extracone space and its diffusion between the intra-and extracone compartments achieving the anesthetic effect.  

Technique ƒƒ ƒƒ ƒƒ ƒƒ

Straight ahead viewing position Percutaneous delivery Needle, maximum 25 gauge, 25 mm Two points of delivery: one at the inferoexternal quadrant (Fig. 4) and the other at the superointernal quadrant beneath the supraorbital notch; injection of 8–10 ml of anesthetic.

Figure 4  Peribulbar anesthesia

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36 ƒƒ Injection of 1 ml subdermal, inferotemporal ƒƒ Compression with Honan balloon

Benefits ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

High safety profile Less pain during injection Lowered risk of optic nerve damage Method of choice in myopes Avoids facial block due to diffusion of the anesthetic to the eyelids

Drawbacks ƒƒ ƒƒ ƒƒ ƒƒ

Slow diffusion, takes 10 minutes to take effect Greater volume of anesthetic needed Greater risk of chemosis and ecchymosis Hyaluronidase needed

Sub-Tenon’s Anesthesia Described by Swan in 1956,32 the sub-Tenon’s procedure is gaining popularity since its efficacy matches that of the aforementioned techniques33,34 and it is recommended for vitreoretinal surgery.35,36 Its main features are: ƒƒ Diffusion of the anesthetic in the subtenonian space and its posterior diffusion from here to block the ciliary nerves ƒƒ Simple technique ƒƒ Reduced pain, rapid effect ƒƒ May be intraoperatively repeated. Useful for peritomy in retinal detachment

Technique ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

Administered as eye drops Conjunctival button hole 4 mm from the nasal limbus or inferior-temporal Blunt dissection of Tenon’s capsule Introduction of 2–4 ml of anesthetic A curved Greenbaum 25 mm cannula is used which adapts to the convexity of the ocular globe (Fig. 5).

Complications ƒƒ ƒƒ ƒƒ ƒƒ

Conjunctival chemosis Incomplete akinesia Risk of conjunctival bleeding Risk of damaging vorticose veins

Chapter 4   Anesthesia

37

Figure 5  Greenbaum cannula used to deliver a peribulbar anesthetic

Our technique: transconjunctival retrobulbar anesthesia Given its unquestionable benefits, we prefer to use local anesthesia for routine vitreoretinal surgery. We use intravenous propofol as an adjuvant (Fig. 6), which is a short-acting, rapid-recovery hypnotic agent. The half-life of propofol in the blood system is around 2.5 minutes, after which it is processed in the liver and is fully eliminated within 55 minutes. Propofol rapidly induces a loss of consciousness, some 30–45 seconds after administration. The recommended intravenous dose of propofol is 1–2.5 mg/kg. This dose should be decreased if propofol is given concomitantly with anxiolytics, opioids or in elderly or hemodynamically compromised patients. Propofol seems to have a protective effect against postoperative nausea and vomiting.8-10

Figure 6  Ampoule of the hypnotic agent propofol administered intravenously along with the local anesthesia

Step by Step Vitrectomy

38 The local anesthetic we use is a 50:50 mixture of 2% mepivacaine (of rapid onset) and 0.75% bupivacaine (of prolonged duration) administered with hyaluronidase to improve diffusion (Fig. 7). Patient monitoring: before surgery, the patient’s level of consciousness is assessed according to his/her verbal capacity and temporal-spatial orientation. Adequate lung ventilation is ensured using nasal spectacles: oxygenation is controlled by pulse oximetry (a noninvasive method of monitoring oxygenhemoglobin saturation). Blood pressure is also monitored using a digital pressure gauge (stress causes the release of catecholamines with the subsequent risk of tachycardia and hypertension) that takes readings every 15 minutes. Possible arrhythmia and ischemia are also verified in a continuous ECG. An intracone retrobulbar injection is given through the conjunctiva as follows: ƒƒ First, a few drops of tetracaine are instilled in the conjunctiva. 1–2 ml of propofol is then given intravenously followed by a 30–40 seconds waiting period. The patient is asked to look directly ahead. ƒƒ A 30 mm long, 25-gauge retrobulbar needle is introduced in the inferotemporal quadrant through the conjunctiva (Fig. 8). ƒƒ The needle is slid along the globe wall with the slanted tip facing the wall to avoid perforations. ƒƒ The needle is advanced through the septum, which is barely perceivable, especially in older subjects, until we reach the muscle cone wall between the inferior and lateral recti, pushing softly (Fig. 9). ƒƒ The possibility of vessel puncture is ruled out by slight aspiration before introducing 2–4 ml of anesthetic in the muscle cone. As the syringe is withdrawn, further anesthetic is injected, checking orbital pressure to avoid

Figure 7  Ampoules containing mepivacaine 2%, bupivacaine 0.75% and hyaluronidase. A 10 ml syringe and 25 gauge, 30 mm long retrobulbar needle

Chapter 4   Anesthesia

39

Figure 8  To initiate the transconjunctival injection process, the surgeon pulls the eyelids apart with the index and thumb

Figure 9  Sliding the needle along the globe wall and introducing it in the transconjunctival muscle cone

inducing high pressure. In this maneuver we usually introduce around 6–8 ml, which is sufficient for surgery (Fig. 10). ƒƒ The eye is gently massaged, and intraocular and intraorbital pressures are manually checked. This procedure gives rise to a slightly protruding, or exophthalmic, globe facilitating subsequent surgical access. It also gives direct access to the muscle cone in a more controlled manner than through the eyelid. So far, we have not experienced any of the complications associated with Atkinson’s retrobulbar anesthesia such as intraocular perforation, retrobulbar hemorrhage, intravascular injection or subarachnoid injection. Surgery is always conducted

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40

Figure 10  Transconjunctival retrobulbar anesthesia. First, the needle is slid along the globe wall to cross the septum. Next, the needle is pointed downwards into the muscle cone. Overcoming the resistance of the muscle cone, the anesthetic is introduced after aspiration

slowly, carefully traversing the orbital septum and muscular cone followed by aspiration. When operating on young patients who require placement of a scleral graft, a further injection of the intracone mixture can be given while manipulating the muscles or the anesthetic can be directly instilled at the insertion points of the rectus muscles.

REFERENCES 1. Charles S, Fanning GL. Anesthesia considerations for vitreoretinal surgery. Ophthalmol Clin North Am. 2006;19(2):239-43. 2. Local Anesthesia for Intraocular Surgery. London: Royal College of Anesthetists and Royal College of Ophthalmologists; 2001. 3. Oh J, Smiddy WE, Kim SS. Antiplatelet and anticoagulation therapy in vitreoretinal surgery. Am J Ophthalmol. 2011;151(6):934-9. 4. Kallio H, Paloheimo M, Maunuksela EL. Haemorrhage and risk factors associated with retrobulbar/peribulbar block: a prospective study in 1383 patients. Br J Anaesth. 2000;85(5):708-11. 5. Wolf GL, Capuano C, Hartung J. Nitrous oxide increases intraocular pressure after intravitreal sulfur hexafluoride injection. Anesthesiology. 1983;59(6):547-9. 6. Stinson TW, Donlon JV. Interaction of intraocular air and sulphur hexafluoride with nitrous oxide: a computer simulation. Anesthesiology. 1982;56(5):385-8. 7. Smith RB, Carl B, Linn JG, et al. Effect of nitrous oxide on air in vitreous. Am J Ophthalmol. 1974;78(2):314-7. 8. Vann MA, Ogunnaike BO, Joshi GP. Sedation and anesthesia care for ophthalmologic surgery during local/regional anesthesia. Anesthesiology. 2007;107(3):502-8. 9. Morley HR, Karagiannis A, Schultz DJ, et al. Sedation for vitreoretinal surgery: a comparison of anesthetist-administered midazolam and patient controlled sedation with propofol. Anaesth Intensive Care. 2000;28(1):37-42.

Chapter 4   Anesthesia

41 10. Habib NE, Balmer HG, Hocking G. Efficacy and safety of sedation with propofol in peribulbar anaesthesia. Eye (Lond). 2002;16(1):60-2. 11. Johnson RW. Anatomy for ophthalmic anesthesia. Br J Anaesth. 1995;75(1):80-7. 12. Dutton JJ, Hasan SA, Edelhauser HF, et al. Anesthesia for intraocular surgery. Surv Ophthalmol. 2001;46(2):172-84. 13. Ripart J, Lefrant JY, de la Cussaye JE, et al. Peribulbar versus retrobulbar anesthesia for ophthalmic surgery: an anatomical comparison of extraconal and intraconal injections. Anesthesiology. 2001;94(1):56-62. 14. Karampatakis V, Natsis K, Gigis P, et al. Orbital depth measurements of human skulls in relation to retrobulbar anesthesia. Eur J Ophthalmol. 1998;8(2):118-20. 15. Knapp H. On cocaine and its use in ophthalmic surgery. Arch Ophthalmol. 1884;13:402-8. 16. Atkinson WS. The development of ophthalmic anesthesia. Am J Ophthalmol. 1961;51:1-14. 17. Morgan CM, Schatz H, Vine AK, et al. Ocular complications associated with retrobulbar injections. Ophthalmology. 1988;95(5):660-5. 18. Hamilton RC, Grizzard WS. Complications. In: Gills JP, Hustead RF, Sanders DR (Eds). Ophthalmic Anesthesia. New Jersey: Slack Incorporated; 1993. pp. 187-202. 19. Edge KR, Nicoll JM. Retrobulbar hemorrhage after 12,500 retrobulbar blocks. Anesth Analg. 1993;76(5):1019-22. 20. Cionni RJ, Osher RH. Retrobulbar hemorrhage. Ophthalmology. 1991;98(8):1153-5. 21. Schneider ME, Milstein DE, Oyakawa RT. Ocular perforation from a retrobulbar injection. Am J Ophthalmol. 1988;106(1):35-40. 22. Edge R, Navon S. Scleral perforation during retrobulbar and peribulbar anesthesia: risk factors and outcome in 50,000 consecutive injections. J Cataract Refract Surg. 1999;25(9):1237-44. 23. Mount AM, Seward HC. Scleral perforations during peribulbar anaesthesia Eye (Lond). 1993;7(Pt 6):766-7. 24. Pautler SE, Grizzard WS, Thompson LN, et al. Blindness from retrobulbar injection into the optic nerve. Ophthalmic Surg. 1986;17(6):334-7. 25. Rosenblatt RM, May DR, Barsoumian K. Cardiopulmonary arrest after retrobulbar block. Am J Ophthalmol. 1980;90(3):425-7. 26. Hamilton RC. Brain-stem anesthesia as a complication of regional anesthesia for ophthalmic surgery. Can J Ophthalmol. 1992;27(7):323-5. 27. Capó H, Roth E, Johnson T, et al. Vertical strabismus after cataract surgery. Ophthalmology. 1996;103(6):918-21. 28. Nayak H, Kersey JP, Oystreck DT, et al. Diplopia following cataract surgery: a review of 150 patients. Eye (Lond). 2008;22(8):1057-64. 29. Liu C, Youl B, Moseley I. Magnetic resonance imaging of the optic nerve in extremes of gaze. Implications for the positioning of the globe for retrobulbar anaesthesia. Br J Ophthalmol. 1992;76(12):728-33. 30. Davis DB, Mandel MR. Posterior peribulbar anesthesia: an alternative to retrobulbar anesthesia. J Cataract Refract Surg. 1986;12(2):182-4. 31. Bloomberg LB. Administration of periocular anesthesia. J Cataract Refract Surg. 1986;12(6):677-9. 32. Swan KC. New drugs and techniques for ocular anesthesia. Trans Am Acad Ophthalmol Otolaryngol. 1956;60(3):368-75. 33. Stevens JD. A new local anesthesia technique for cataract extraction by one quadrant sub-Tenon’s infiltration. Br J Ophthalmol. 1992;76(11):670-4.

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42 34. Friedman DS, Bass EB, Lubomski LH, et al. Synthesis of the literature on the effectiveness of regional anesthesia for cataract surgery. Ophthalmology. 2001;108(3):519-29. 35. Li HK, Abouleish A, Grady J, et al. Sub-Tenon’s injection for local anesthesia in posterior segment surgery. Ophthalmology. 2000;107(1):41-6. 36. Calenda E, Olle P, Muraine M, et al. Peribulbar anesthesia and sub-Tenon injection for vitreoretinal surgery: 300 cases. Acta Ophthalmol Scand. 2000;78(2):196-9.

Chapter 5

Instrumentation José Juan Martínez-Toldos, Cristian Fernández-Martínez

5.1  OPERATING ROOM INTRODUCTION In the operating room, the surgeon seeks maximal independence. This means having systems that the surgeon and assisting nurses can control without the need for third parties.1 The personnel needed are: surgeon, nurse, instrument technician, circulating nurse and anesthetist. Each member of the operating team should know his/ her site of action in the room. The surgeon usually stands nearby the patient with the technician to his/her right where he/she can control the instrument tray and ensure the equipment is functioning correctly. The anesthetist usually stands/sits at the foot of the operating table and controls the monitoring of electrocardiogram (ECG), arterial blood pressure and partial pressure of oxygen in the blood. Finally, the nurses provide the equipment needed for each stage of surgery and ensure the correct functioning of the machines.2

REQUIREMENTS Ophthalmologic Surgery Table The operating table or stretcher is used for both transport and surgery so that the patient does not have to be transferred to another operating bench. It should be articulated with an adjustable headrest to comfortably change the patient’s head position. The eye-plane should be parallel to the ceiling as a downward or upward inclination will impair the surgeon’s vision and hinder the surgery. The

Step by Step Vitrectomy

44 upholstery should be comfortable since we are dealing with elderly patients under local anesthesia. When surgery lasts for more than an hour, common complaints have more to do with the patient becoming restless and uncomfortable than the intraocular surgery itself; an uncomfortable patient is less willing to cooperate (Fig. 1). In addition, the operating table should easily convert into a reclining chair to help incorporate and position the patient after surgery. Electrical stretchers also exist with batteries to power the articulation and movement of the main body and headrest. This means the patient’s position can be adjusted without physical help required. Before starting the surgery, it should be checked that the batteries are fully charged to avoid surprises during an intervention (Fig. 2).

Figure 1  Stryker stretcher for ophthalmology surgery. The table is articulated and has a hydraulic up/down movement system allowing adjustment of the headrest so that the patient’s head can be correctly positioned horizontally leaving sufficient room for the surgeon’s feet and control pedals

Figure 2  Electrical stretcher powered by batteries. Its main articulated body can be remote-controlled without the need to touch the stretcher

Chapter 5   Instrumentation

45

Instrument Column There should be a single instrument column to accommodate the vitrectomy system, endolaser, cryotherapy device, infusion fluids and anything else needed for the surgery. The column is positioned at the foot of the operating table (Fig. 3).

Integrated Vitrectomy Systems The improved flow control of the new high-speed vitrectomy systems helps regulate tissue aspiration towards the vitreotome tip. These systems include their own lasers, filters, various illumination devices, intraocular pressure-controlling pumps and dense fluid or gas injection/removal pumps. They do not include a cryotherapy system since their use is becoming less frequent (Figs 4A and B).

Image Recorder This allows direct real-time viewing of the microsurgery procedure and has become indispensable for the members of the operating team, such as the anesthetist and circulating nurses, who have no access to the microscope. The monitor should be positioned such that the surgeon can easily center the image during surgery. The use of a recording system also provides footage of the different surgery procedures for training medical staff or students. Recordings can also be used for presentations. Nowadays, available are the new high-definition digital recording systems. These allow the recordings to be divided into 5, 10 or 15 minutes files. Photographs can also be captured during the intervention.

Figure 3  Instrument column housing the vitreotome equipped with cutter, aspirator, diathermy system, infusion pump, illumination system, an endolaser, infusion fluid support system, etc.

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46

A

B

Figures 4A and B  The new high-speed vitrectomy systems are equipped with lasers, filters, intraocular pressure control pumps, dense fluid injection pumps and tools for phacoemulsification, phacofragmentation, etc. (A) Constellation; (B) Stellaris PC

Operating Microscope For vitreous surgery, a multifunctional microscope3 is required equipped with the following: ƒƒ X-Y system for movement of the microscope head position with respect to the eye: X corresponds to nasal-temporal direction of movement and Y to superoinferior movement. Before the onset of surgery, the X-Y system should be returned to its central position so that the microscope head can be moved in any direction4,5 ƒƒ Zoom: Controlled by the surgeon using a foot pedal ƒƒ Articulated arms: To easily move the microscope ƒƒ Fine focus: At high magnification, the depth of the field decreases and focusing becomes more difficult. Thus, sometimes it is best to reduce the magnification for fine focusing and then gradually increase magnification to obtain the desired image size ƒƒ On/off switch: Controlled by the surgeon using the footswitch. This avoids the need for movement of ancillary staff ƒƒ Laser filter and an image inverting system when using a wide-field viewing system ƒƒ A binocular eyepiece when working with an assistant. The laser filter should be fitted below the division of the two eyepieces so that both the surgeon and the assistant are protected ƒƒ A video camera to transfer the image to the monitor such that the entire operating team can follow the surgical procedure.

Chapter 5   Instrumentation

47 The operating microscope (Fig. 5) is ideally attached to the ceiling allowing more free space in the operating room. If this is not possible, the microscope can be added to the instrument column. In this last case, the microscope is fixed to the operating stretcher at the foot of the patient. Pedal positions (Figs 6A and B) are usually: ƒƒ Microscope pedal, left ƒƒ Vitreotome pedal, right ƒƒ Laser pedal, middle.

Figure 5  Leica microscope with an X-Y sytem, video camera, assistant eyepiece and surgeon eyepiece. A laser filter placed below the eyepieces protects the surgeon and the assistant from the laser

A

B

Figures 6A and B  (A) Left microscope pedal controls X-Y system, microfocus, zoom, on/off switch; (B) Right vitreotome pedal controls aspiration, cutting, infusion pressure, backflush and diathermy. The wireless pedal system eliminates cord clutter

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48

REFERENCES 1. Charles S, Katz A, Wood B. Vitreous Microsurgery, 3rd edition. Philadelphia: Lippincott Williams and Wilkins; 2002. pp. 25. 2. Corcóstegui B, Adán A, García-Arumí J, et al. Cirugía vitreoretiniana, indicaciones y técnicas. Madrid: Tecnimedia editorial; 1999. pp. 20-1. 3. Parel JM, Machemer R, Aumayr W. A new concept for vitreous surgery. An automated operating microscope. Am J Ophthalmol. 1974;77:161. 4. Charles S, McCarthy C, Eichenbaum D. A chin-operated switch for motorized three-axis microscopic movement. Am J Ophthalmol. 1975;80(1):150-1. 5. Freeman HM, Tolentino FI. Atlas of Vitreoretinal Surgery. New York: Thieme Medical Publishers; 1990. pp. 40-3.

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49

5.2  VISUALIZATION SYSTEMS INTRODUCTION Since the advent of vitreoretinal surgery, contact lenses bearing a ring to fix the lens to the sclera, 2 mm from the limbus, have been used. Lenses are generally oriented at 6–12 hours,1,2 although they may also be positioned horizontally or obliquely if the eye has been subjected to previous surgery preventing good anchorage (Fig. 1). Currently, there are contact lenses with a silicone selfretaining ring that do not require suturing to the sclera (Fig. 2). In 1999, self-stabilizing contact lenses for vitrectomy were developed (Figs 3A and B) without the need for a suture ring or an assistant. Thus, Volk’s self-stabilizing vitrectomy lenses let ophthalmologists perform wide-angle vitreoretinal surgery without a suture-down ring. Currently, a wide-angle high refractive power self-stabilizing lens is available; the so-called ora-ora lens provides a visual field of 154° in static mode and of 190° in dynamic mode, allowing observation of the pars plana and ora serrata.3

Figure 1  Landers lens retaining ring with a wide rim for greater stability even when used to stabilize wide-angle contact lenses

Figure 2  Dorc silicone retaining ring in which a lens can be inserted avoiding the need for suturing to the sclera

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50

A

B

Figures 3A and B  (A) The Volk self-stabilizing vitrectomy lens . Vitrectomies can be performed using wide-angle lenses without the need for scleral suturing or an assistant; (B) Panoramic view of the ultra-wide-angle “ora-ora” lens (Volk Optical, Mentor)

UPRIGHT IMAGE CONTACT LENSES Contact lenses offset the high convergent power of the curvature of the cornea, allowing the operating microscope to focus on the central vitreous or posterior retina. Although they provide a good quality direct image, (Fig. 4) the few degrees of visual angle offered means they have to be constantly rotated and frequently interchanged to work in peripheral areas. For years, vitreous surgery lenses have been responsible for the success of this type of surgery and in every vitreoretinal operating room there should be a set of lenses (Fig. 5) comprising:

Landers Biconcave Lens A 90D lens for viewing the fundus through an air-filled globe in phakic or aphakic eyes. This lens provides a 25° viewing angle and image magnification of 0.8x.

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51

Figure 4  The Machemer magnifying contact lens provides an upright 28° to 30° image

Figure 5  Conventional vitrectomy lens pack supplied by Dorc including: a biconcave lens (brown) for visualization of the fundus in an air-filled phakic eye; a flat (gold) lens for the central vitreous and fundus; a 20° prism lens (green) for the posterior periphery; a wide-angle lens (blue) for the central posterior fundus and central vitreous; and a 30° prism lens (purple) for the periphery beyond the equator

Machemer Magnifying Lens This lens allows observation of retinal surface details. Its viewing angle is 30° and magnification 1.49x.

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Figure 6  Disposable silicone lenses marketed by Dorc that do not require a stabilizing ring

Peyman Wide-angle Lens The concave anterior surface of this lens provides a viewing angle from 48° to the equator and a magnification of 0.49x.

Machemer Plano-concave Lens It provides a viewing angle of 36° and a magnification of 1.02x.

Tolentino Twenty Degree Prism Lens This lens, for the periphery, offers a viewing angle of 36° and a magnification of 1.02x.

Tolentino Thirty Degree Prism Lens It is a lens for the extreme periphery with a viewing angle of 33° and a magnification of 1.02x.

Woldoff Biconcave Prism Lens It allows the periphery to be viewed in a gas-filled eye. Its viewing angle is 18° and magnification is 0.40x. Also available are disposable silicone lenses that do not require a suture ring (Fig. 6). These may be used for routine vitreoretinal surgery or for specific procedures when working in a wide field, for instance on the macula.

WIDE-ANGLE-VIEWING SYSTEMS Indirect contact lens systems were developed for panretinal photocoagulation, allowing a wide field of visualization of the retina through small pupils.

Chapter 5   Instrumentation

53 However, these lenses produced an inverted image initially, preventing their use in surgery. The problem was overcome in 1987, when Spitznas and Reiver4 developed the stereoscopic diagonal inverter (SDI) to reinvert the stereoscopic image. This was followed by the emergence of the binocular indirect ophthalmomicroscope (BIOM), which provides good quality, noncontact images of the retina, allowing the surgeon to work with wide-viewing fields within the eye.5 The BIOM procedure has led to the development of several wide-angle-viewing systems using contact or noncontact lenses, facilitating many of the maneuvers used in vitreous surgery.6 Wide-angle-viewing systems with an image inverter incorporated in the body of the microscope include: ƒƒ The BIOM/SDI noncontact system with or without a miniature, indirect viewing contact lens (field of view 70°, 90° or 110°) (Figs 7A and B ƒƒ The Volk reinverting operating lens system used with both standard lenses and the new self-stabilizing lenses of 58D, 85D or 156D for visualization up to the vitreous and ora serrata (contact system) ƒƒ The advanced visual instruments (AVI) inverter with an indirect contact lens of 68D and 130D (contact system) (Fig. 8) ƒƒ The iris medical contact wide-angle system (contact system) ƒƒ Optiflex with a manual or automated system ƒƒ Optical fiber free intravitreal surgery system (OFFISS) incorporated in Topcon’s OMS-800 microscope (noncontact system). These contact and non-contact systems (Table 1) have the common feature that the image inverting system is mounted in the microscope body separate from the lenses. Some wide-angle viewing systems do not require an image inverting system in the microscope (Table 2), such as:

A

B

Figures 7A and B  (A) Wide-field BIOM system mounted in the microscope fitted with a fine focusing wheel. The image-inverting device is incorporated in the microscope; (B) Working with the BIOM system

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54

Figure 8  AVI inverting system used with 68D and 130D lenses. Note the contact lenses with Landers stabilizing rings

TABLE 1 Contact wide-angle systems (Advanced Visual Instruments, Iris Medical, Volk) Benefits

Drawbacks

• • • •

• • • • • •

Excellent panoramic view of fundus Wide angle of vision Work in the periphery possible Air/fluid interchange possible

Learning curve required Trained assistant required Image inverter required Indentation difficult Presence of blood impairs vision Usually several lenses need to be interchanged

ƒƒ The EIBOS (erect indirect binocular ophthalmic system) is a noncontact

system, with a single component indirect viewing device/image reinverter. The EIBOS provides a visual field of 100° with 90D lenses and 125° With XL lens of 132 D (Figs 9A and B). ƒƒ The Peyman-Wessels-Landers 132D upright vitrectomy lens has an internal prism system that gives an upright wide-angle image. The image is focused using the pedal. In the past, we have worked with classic contact lenses, Landers suture rings, and the contact wide-angle AVI system and noncontact EIBOS system, which give us at least a 100° panoramic image (Fig. 10). Presently, we use the noncontact EIBOS method. This procedure allows us to work more independently without the need for an assistant or lens interchange. The problem of limited peripheral vision is well resolved by two strategies: tilting the eye, making small microscope movements in the desired direction and reaching the ora serrata with peripheral indentation. This last maneuver is achieved with the

Chapter 5   Instrumentation

55 TABLE 2 Noncontact wide-angle systems (BIOM, EIBOS, OFFISS, Peyman) BIOM-OFFISS

EIBOS-Peyman-Leica

Benefits: • Wide field of panoramic vision • Easy handling of globe • Indentation possible • No assistant needed • Work with narrow pupils and some corneal opacity possible • Good air/fluid exchange visualization

Benefits: • Direct panoramic image seen upright • X-Y movements in correct direction, subtle • Easy handling of globe • Indentation, work with small pupils, fluid/air exchange possible • Easy focusing • No assistant needed • No inverter needed

Drawbacks: • Inverter needed • X-Y movements in opposite direction • Learning curve required

Drawbacks: • 120° of maximum vision • Short learning curve needed • Indentation needed to see ora serrata and pars plana

Abbreviations: BIOM: Binocular indirect ophthalmomicroscope; OFFISS: Optical fiber free intravitreal surgery system; EIBOS: Erect indirect binocular ophthalmic system

A

B

Figures 9A and B  (A) Noncontact EIBOS system supplied by Möller-Wedel. This system has its own image reinverting system to produce an upright image avoiding the need for a microscope-mounted inverter; (B) Upright 100° image provided using a 90D lens

cryotherapy probe, providing excellent indentation. Recently, a similar system to EIBOS has been introduced by Leica that can, nevertheless, only be used with the company’s own RUV800 microscope (Fig. 11).

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Figure 10  Panoramic view achieved with a wide-angle-viewing system of 100° to 135°

Figure 11  Leica RUV800 noncontact retinal viewing system. A new system similar to EIBOS has been introduced by Leica

Use of the Erect Indirect Binocular Ophthalmic System The nonsterile block (optical system with inverter) is placed in the microscope. Once fixed, the sterile silicone cover and manual focusing device are positioned by the surgeon. The working sterile lens is also put in place. This lens will be of 90D if we need to work in the macular region, while an XL lens is used when treating a detached retina, vitreoretinal proliferation or when working more in the periphery. We then set the microscope focus at “0” and center the X-Y movement motor. The microscope is lowered or raised until we can see the anterior pole well without altering the focus.

Chapter 5   Instrumentation

57 At this stage in the procedure, we can see the anterior pole well and the EIBOS still has its sterile cover and is retracted behind the microscope’s optics. We then introduce the endo-ocular light source, place the EIBOS under the microscope’s optics and switch off the microscope light. Next, we observe the light in the vitreous, focus the probe using the manual focus of the EIBOS and increase the zoom. We then lower the EIBOS a little to increase the field of view and do not touch the microscope’s focus again. Fine focusing is achieved using the manual device of the EIBOS (Figs 12A and B). To avoid the need to constantly irrigate the cornea and avoid epithelial edema or having to remove the epithelium, at the start of the surgery we place a viscoelastic substance on the cornea and then with a few drops of saline we can create a smooth surface allowing good visualization of the fundus. When we have difficulty in viewing the posterior segment, we use a magnifying contact lens with a silicone ring to work at the level of the macula. In some cases, we use a biconcave lens for fluid/air exchange, especially in phakic patients with considerable myopia. We can undertake fluid/air exchange placing the biconcave lens in the EIBOS and thus have a panoramic view for the maneuver in difficult eyes.

A

B

Figures 12A and B  (A) The surgeon achieves fine focus using the index finger; (B) Use of the EIBOS system showing the working distance and sterile silicone drape covering the instrument

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58

OTHER VISUALIZATION SYSTEMS In 2003, Peyman and Landers7 launched a new wide-angle-viewing system (Peyman-Wessels-Landers) fitted to an inverter such that this component does not have to be placed in the body of the microscope. The system is similar to the EIBOS in that there is no need for a microscope-mounted image inverter (Figs 13A and B). Recently, a new holding device has been introduced that consists of a rotating bar and lens holder.8 In 2004, Topcon started marketing the OFFISS that can be fitted to the new OMS-800 microscope with its lens stabilizing system. The OFFISS provides an inverted image and therefore requires a microscope-mounted inverter. The microscope is fitted with its own illumination system that condenses the light through the lenses to visualize the fundus and work in the eye without really needing endoillumination fiber optics. Since the light emitted is diffuse, it illuminates the entire ocular globe well. To improve light focusing on tissues, it also has an incorporated slit lamp. The lenses currently available are 40D and 87D, giving 60° and 120° viewing angles. The great advantage of OFFISS is that most vitrectomy procedures can be undertaken with two ports for infusion and instrumentation. Also, in the

A

B

Figures 13A and B  (A) Wide-angle noncontact system designed by Peyman, Wessels and Landers for ocular instruments. This system incorporates an image reinverter so there is no need for a microscope-mounted inverter; (B) Rotating bar (arrow) and lens holder (asterisk)

Chapter 5   Instrumentation

59 case of bimanual surgery, three ports can be used (one for infusion and two for sclerotomy) along with the normal instrumentation without the need for an optic fiber light. Among its drawbacks, we could mention the need for a microscope-mounted inverter and for some amount of training to be able to work comfortably (Figs 14A to C). Some ophthalmologists prefer to view the vitreous in retinal surgery by angling the light from the microscope’s slit lamp by 5°. Using this technique, it is possible to work in the macular region using a Machemer lens and only two ports for infusion and instrumentation. The method, especially used by the French school, provides a good view of the posterior pole when removing epiretinal membranes, internal limiting membrane, subretinal membranes, etc.

A

B

Figures 14A and B

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60

C

Figure 14C

Figures 14A to C  (A) Topcon’s OFFISS system with the lens fixed to the microscope; (B) Bimanual surgery performed only with light from the microscope; (C) Slit lamp view

To work in the periphery, the Goldmann three mirror lens needs to be used; requiring constant rotation. Several microscopes currently have an incorporated slit lamp including Zeiss’ OPMI VISU and the new Möeller model, which allows the surgeon to work with light from the microscope and a contact lens on the cornea (Figs 15A and B; Fig. 16).

A

Figure 15A

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61

B

Figure 15B

Figures 15A and B  (A) Working with the microscope’s slit lamp and using only two ports for infusion and instrumentation; (B) Machemer contact lens

Figure 16  Zeiss microscope with slit lamp

COMBINED PROCEDURES We can combine slit lamp illumination with the use of wide-angle contact lenses to give a panoramic view allowing the detailed observation of the retinal periphery9 (Figs 17A and B). The main shortcoming of this method is that glare is produced with slit lamp-illuminated contact lenses. To avoid this, multicoated

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A

B

Figures 17A and B  (A) View of the posterior pole using a slit lamp and wide-angle contact lens; (B) View of the periphery with indentation Source: Reproduced with permission from Ohji M, Tano Y. Vitreoretinal surgery with slit-lamp illumination combined with a wide-angle-viewing contact lens. Am J Ophthalmol. 2004;137(5):955-6

antireflective contact lenses are used that provide a clear image of the retina without glare10 (Figs 18A and B). To avoid the cornea drying during vitrectomy, we can use the new antidrying corneal contact lens for a noncontact wide-angle-viewing system. The viscoelastic is placed on the cornea and over this, the lens is positioned using a

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A

B

Figures 18A and B  (A) Retina viewed with the slit lamp and a multicoated contact lens; (B) Bimanual surgery performed using the same combination Source: Reproduced with permission from Kadonosono K, Kamezawa H, Uchio E, et al. Bimanual vitreous surgery with slit-beam illumination and multicoated contact lens. Retina. 2006;26(6):708-9

sutureless stabilizing ring. This technique offers clear panoramic visualization of the retina throughout the entire surgical procedure11 (Fig. 19). Finally, it is possible to fit an ocular coherence tomography system to the microscope’s beam splitter. This allows tomographic monitoring during surgery, aiding decision making both during and following surgery.12

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Figure 19  Quartz lens with a refractive power of zero placed on the cornea Source: Reproduced with permission from Ohno H, Inoue K. An antidrying corneal contact lens for a noncontact wide-angle viewing system. Retina. 2011;31(7):1435-6

REFERENCES 1. Freeman HM, Tolentino FI. Atlas of Vitreoretinal Surgery. New York: Thieme Medical Publishers; 1990. pp. 11-2. 2. Charles S, Katz A, Wood B. Vitreous Microsurgery, 3rd edition. Philadelphia: Lippincott Willians and Wilkins; 2002. pp. 37. 3. Murthy R, Brar V, Chalam K. Evaluation of ultra wide angle “ora-ora” high refractive index self-stabilizing contact lens for vitreous surgery. Retina. 2010; 30(9):1551-3. 4. Spitznas M, Reiner J. A stereoscopic diagonal inverter (SDI) for wide-angle vitreous surgery. Graefes Arch Clin Exp Ophthalmol. 1987;225(1):9-12. 5. Spitznas M. A binocular indirect ophthalmomicroscope (BIOM) for non-contact wide-angle vitreous surgery. Graefes Arch Clin Exp Ophthalmol. 1987;225(1):13-5. 6. Lesnoni G, Billi B, Rossi T, et al. The use of panoramic viewing system in relaxing retinotomy and retinectomy. Retina. 1997;17(3):186-90. 7. Landers MB, Peyman GA, Wessels IF, et al. A new, non-contact wide field viewing system for vitreous surgery. Am J Ophthalmol. 2003;136(1):199-201. 8. Kakinoki M, Hirakata A, Landers MB, et al. The new lens holder for PeymanWessels-Landers 132D upright vitrectomy lens. Retina. 2010;30(8):1316-7. 9. Ohji M, Tano Y. Vitreoretinal surgery with slit-lamp illumination combined with a wide-angle-viewing contact lens. Am J Ophthalmol. 2004;137(5):955-6. 10. Kadonosono K, Kamezawa H, Uchio E, et al. Bimanual vitreous surgery with slit-beam illumination and multicoated contact lens. Retina. 2006;26(6):708-9. 11. Ohno H, Inoue K. An antidrying corneal contact lens for a noncontact wide-angleviewing system. Retina. 2011;31(7):1435-6. 12. Binder S, Falkner-Radler C, Hauger C, et al. Feasibility of intrasurgical spectraldomain optical coherence tomography. Retina. 2011;31(7):1332-6.

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5.3  ENDOILLUMINATION SYSTEMS INTRODUCTION A good source of light is needed to illuminate the intraocular tissue that is to be removed. The source can be an external light that crosses the transparent media of the globe and lights its inner structures. Alternatively, fiber optic light pipes can be introduced through sclerotomies to directly illuminate the tissues.

EXTERNAL SYSTEMS As an external light source, we can use the light from the slit lamp attached to the microscope, which with the help of corneal contact lenses, allows the surgeon to work on the retina. The new optic fiber free intravitreal surgical system also uses light emitted from the microscope.

INTERNAL SYSTEMS The most common illumination method is the use of a direct endo-ocular light that can be introduced into the eye through probes, the infusion port or fitted to the instruments used. The endoillumination probe is the most frequently used and is the light source we generally use. The tips of 20- or 25-gauge probes are perpendicularly cut to provide concentrated light in a given area and a certain slit lamp effect, offering good vision of the peripheral vitreous. Depending on the distance from the tissue, we will obtain a greater or smaller illuminated field. As we approach the retina, we will have more light yet a smaller illuminated field and vice versa as we move away from the retina. These probes can be fitted with picks and spatulas to facilitate surgical maneuvers (Figs 1A and B). Bullet type fibers provide wide-angle illumination, diffusely lighting the surgical field, and are thus useful when working with wide-angle viewing systems and for exchange maneuvers, but are inappropriate for working on the retina since they cannot be used to focus light on a given spot. These optical fibers are usually introduced through the infusion port and are used as an additional light source for bimanual surgery procedures. When a fiber optic is used in the infusion system, the irrigation pressure should be increased and aspiration needs to be more carefully controlled. Forceps and scissors are the instruments generally fitted with a fiber optic light (Fig. 2) but these instrument have to be turned inwards, towards the tissue, to avoid generating glare. In addition, shadows may be produced. Currently, we have instruments available with an incorporated fiber optics such that they do not have to be mounted during surgery. These ready to use instruments may even be disposable.

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A

B

Figures 1A and B  (A) Straight 20-gauge endoillumination probe. Probe with membrane pick and bullet type probe; (B) Panoramic illumination probe

Figure 2  Segmenting/delaminating scissors with an incorporated light source

We can introduce a supplementary optic fiber through a 0.5 mm incision for several bimanual maneuvers, suturing the fiber to the sclera. When removing the optic fiber there is no need to close the wound since it is sufficiently small. Light incorporated in the laser probe is very useful, since it frees up one of the surgeon’s hands for indentation during photocoagulation. Retractile curved probes also exist that facilitate photocoagulation in the superior zone. There are also optic fibers combined with an irrigation cannula such that some vitrectomies can be performed with only two-port openings or bimanual surgery can be conducted with illumination in the infusion zone. Another device, the tissue manipulator with its functions of illumination, diathermy and aspiration, 1 was designed to treat retinal fibrovascular proliferations as in diabetic retinopathy, but may also be used to manipulate tissues in other circumstances (Fig. 3). More complex endoillumination systems exist such as the multiport illumination system (MIS). This instrument, with two trocars that need to be

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Figure 3  Tissue manipulator for: (1) Illumination, (2) Diathermy, and (3) Aspiration

inserted through a cross-shaped incision, provides illumination controlled by 20-gauge instruments introduced via the trocars, which remain fixed to the sclera throughout the operation.2-4 The MIS can be used for bimanual surgery without the need for illuminating instruments. Its main shortcoming is that a scleral incision larger than 0.9 mm is needed (Figs 4A and B) and it has not been too widely adopted. Yet another illumination system is the Tornambe mini-light system that can be introduced through a 25-gauge incision and does not require sutures to close the incision wound once removed. Four mini-lights can be used at a time to avoid shadowing by the instruments. This system is used for wide-field and bimanual surgery (Figs 5A and B). Today, individual 25-gauge Tornambe lights can be purchased that provide good illumination of the top zone.

CHANDELIER SYSTEM A recent appearance in the market that can be used for bimanual surgery without illuminated instruments is the 25 gauge Awh Microfiber™ Sutureless Chandelier which illuminates the entire posterior segment. Surgery with 25-gauge instruments can be comfortably conducted and membranes can be removed bimanually. Due to its small caliber it does not require suturing and has a stabilizing system. Although a fourth side-port opening is required to introduce the light source, permanent light is provided during the entire operation (Figs 6A to C). Modifications to the system have included the incorporation of 27 and 29 gauges and a new mercury vapor light source (Photon II), which reduces retinal phototoxicity and allows for the use of laser fiber optics. The light emitted is yellowish green5 (Figs 7A to C).

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A

B

Figures 4A and B  (A) The multiport illumination system avoids the need for illuminated instruments in bimanual surgery; (B) Light providing trocar through which instruments are introduced; currently unused

A

B

Figures 5A and B  (A) System comprised of small torpedoes that illuminate the eye without producing shadows. The 0.5 mm incisions needed can be transconjunctival; (B) Tornambe mini-light system from Insight Instruments is very little used at present

B

A

C

Figures 6A to C  (A) Synergetics light source; (B) Image of the chandelier showing its 25-gauge optic fiber; (C) Chandelier in a pars plana position without sutures

A

B

C

Figures 7A to C  (A) Photon I and Photon II; (B) Photon II screen, exit for mercury vapor light and for laser; (C) Yellowish green appearance of the retina

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69 Endoillumination systems have been improved to avoid the need for suturing in place. The new 27-gauge twin probe is an example. It provides panoramic illumination avoiding shadows. To help introduce a twin probe, we used the edge of a 27-gauge needle to perforate the sclera6 (Figs 8A and B). Illuminated vitrectomy probes are now available that allow the surgeon to conduct an efficient peripheral vitrectomy with the help of indentation, since this system frees the hand that normally held the endoillumination probe (Fig. 9). A new illumination system, the ocuLED, is based on light emitting diode technology. This device provides brilliant light that is scarcely toxic since its emission spectrum is far from that of blue light.7 Any type of light (especially short wavelength, or blue/violet light)8-10 close to the retina can cause phototoxic retinal lesions. To avoid this, the macula should be illuminated for just the necessary amount of time using the minimum intensity of light. Any preretinal bleeding should be dealt with at the end of the surgical procedure since this acts as an excellent protective filter for the retina.

A

B

Figures 8A and B  (A) 27-gauge twinlight Chandelier illumination system; (B) Maneuver to introduce the probe Source: Reproduced with permission from Eckardt C, Eckert T, Eckardt U. 27-gauge twinlight chandelier illumination system for bimanual trans conjunctival vitrectomy. Retina. 2008;28(3):518-9

Figure 9  Illuminated 20-gauge vitrectomy probe from Dorc

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REFERENCES 1. McCuen BW, Hickingbotham D. A fiberoptic diathermy tissue manipulator for use in vitreous surgery. Am J ophthalmol. 1984;98(6):803-4. 2. Koch FH, Pawlowski D, Spitznas M. A multiport illumination system for panoramic bi-manual vitreous surgery. Graefes Arch Clin Exp Ophthalmol. 1991; 229(5):425-9. 3. Boker T, Augustin AJ, Schmidt H, et al. Larger sclerotomies for use of the multiport illumination system do not increase the complication risk of vitrectomy. Klin Monbl Augenheilkd. 1995;206(2):78-82. 4. Steinmetz RL, Grizzard WS, Hammer ME. Vitrectomy for diabetic traction retinal detachment using the multiport illumination system. Ophthalmology. 2002;109(12):2303-7. 5. Oshima Y, Chow DR, Awh CC, et al. Novel mercury vapor illuminator combined with a 27/29-gauge chandelier light fiber for vitreous surgery. Retina. 2008;28(1):171-3. 6. Eckardt C, Eckert T, Eckardt U. 27-gauge Twinlight chandelier illumination system for bimanual transconjunctival vitrectomy. Retina. 2008;28(3):518-9. 7. Dithmar S, Hoeh AE, Amberger R, et al. Light-emitting diode technology in vitreoretinal surgery. Retina. 2011;31(5):924-7. 8. Fuller D, Machemer R, Knighton RW. Retinal damage produced by intraocular fiber optic light. Am J Ophthalmol. 1978;85(4):519-37. 9. Khun F, Morris R, Massey M. Photic retinal injury from endoillumination during vitrectomy. Am J Ophthalmol. 1991;111(1):42-6. 10. Michels M, Lewis H, Abrams GW, et al. Macular phototoxicity caused by fiberoptic endoillumination during pars plana vitrectomy. Am J Ophthalmol. 1992;114(3):287-96.

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5.4  INFUSION PRESSURE SYSTEM INTRODUCTION To work inside the globe, intraocular pressure (IOP) can be kept constant using two methods: (1) the height of the physiological saline bottle can be adjusted to create hydrostatic pressure or (2) we can use an air pump to constantly pressurize the fluid infusion system.

HYDROSTATIC PRESSURE The difference in height between the bottle (Fig. 1) containing the infusion liquid and the eye being operated on generates a pressure gradient that is transmitted to the inner eye. As we are dealing with a closed circuit, if we raise the bottle 35–40 cm from the level of the eye, we will obtain an IOP between 25 mm Hg and 30 mm Hg. This is the pressure we normally work with to avoid significant collapse of the eye globe during aspiration.1 If bleeding commences during surgery, the bottle should be lifted to 125 cm to control the bleeding episode and then gradually lowered to the working height without removing the intraocular instruments. This last precaution avoids leakage and reduces the risk of tissue incarceration at the sclerotomy sites due to high IOP. It is important to check that the infusion bottle is never without liquid, since this would produce a sudden drop in IOP, accompanied by a risk of bleeding or retinal tears if we are working with the vitreotome, through intense traction on the vitreous caused by the abrupt fall in IOP.

Figure 1  Infusion bottle. When using a positive pressure pump, the bottle is placed at the level of the patient’s head to avoid adding hydrostatic pressure to the infusion pressure provided by the pump

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72 The IOP in mm Hg can be calculated by multiplying the height of the infusion fluid bottle in centimeters by 0.74 (Table 1). IOP = Height of infusion bottle in cm × 0.74

INFUSION PUMP OR GAS FORCED INFUSION In current clinical practice, the height of the infusion bottle is unimportant, since positive pressure pumps are used that continuously pressurize the irrigation system. Thus, the infusion fluid bottle should be at the same level as the patient’s head so that no hydrostatic pressure is added to the pressure achieved by the pump. The pump can be independent from or integrated in the vitrectomy system. The first pumps for pressure control worked by introducing air into the fluid at the bottom of the infusion bottle and this meant that IOP could not be rapidly recovered.2,3 Vented gas forced infusion systems have a trocar that reaches the air chamber in the infusion bottle, so that IOP can be more precisely controlled (Fig. 2) and as air pump pressure falls, so does the pressure in the ocular globe. This is the system we prefer since it allows us to rapidly achieve any IOP changes needed during surgery.4,5 Pressure pumps (Figs 3A and B; Fig. 4) are useful for fluid/air or air/fluid exchange. Using a pump, the surgeon can directly control the filling of the eye with air and thus keep the retina in position when applying the laser or installing some type of tamponade. We can also direct blood toward the posterior pole following intense bleeding by replacing fluid with air. In this way, the infusion and intraocular pressure can be defined as: Infusion pressure = Pump positive pressure + hydrostatic pressure Intraocular pressure = Infusion pressure – aspiration pressure – losses through sclerotomies The Constellation vitrectomy incorporates a new IOP control system. The system consists of a cartridge with fluid movement-measuring sensors. This

TABLE 1 Intraocular pressure according to the position of the irrigation bottle Height of bottle above the eye

Intraocular pressure

  15 cm

11 mm Hg

  25 cm

18.5 mm Hg

  50 cm

37 mm Hg

  75 cm

55 mm Hg

100 cm

74 mm Hg

125 cm

92 mm Hg

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Figure 2  Vented gas forced infusion system. The air filter is connected by pressure to the air outflow port and the three-way valve allows the system to be used with irrigation of fluid/air or to close the system off such that nothing enters the eye

A

B

Figures 3A and B  (A) Positive pressure pump that injects air into the infusion fluid bottle via a vented gas forced infusion trocar reaching the air chamber. The fluid, pushed by the pressure, enters and pressurizes the ocular globe. If we close off the passage of irrigation fluid using the three-way valve, this will allow the entry of air at a given pressure (generally 25 mm Hg) into the globe. To fill the globe with air, intraocular fluid has to be simultaneously aspirated; (B) Accurus pressure pump. The pump blows air through the vented gas forced infusion tubes, pressurizing the bottle, which in turn introduces fluid into the eye when intraocular pressure drops

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Figure 4  Grieshaber pressure pump. The picture shows the air outflow tube with filter, the pressure display and the infusion pipe through which we introduce the system in the globe. This pump is independent of the vitrectomy system

enables the device to offset any pressure differences produced in the infusion line so that a constant IOP is maintained during surgery. This infusion system automatically adjusts the amount of infused saline in response to pressure reductions in the line and infusion cannula. Pressure is maintained at +/– 2 mm Hg with respect to the value indicated by the system (Fig. 5).

Figure 5  The infusion line from the saline bottle directly enters the cartridge from which the eye infusion line emerges. This allows for an immediate response to any change in pressure

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75 The benefits of the Constellation system include the possibility of increasing IOP using the pedal in cases of bleeding. The instrument’s display panel indicates the precise time of high IOP and incorporates an alarm and voice confirmation system.

PRESSURE CONTROL Adequate pressure control is important throughout surgery since any rise or drop in IOP could give rise to problems.

Low Intraocular Pressure Low IOP may lead to: ƒƒ Tendency for retinal bleeding ƒƒ Risk of pupil miosis ƒƒ Striate keratopathy.

High Intraocular Pressure High IOP may lead to: ƒƒ Optic nerve ischemia and visual field defects ƒƒ Jabbing ocular tissue when removing instruments ƒƒ Corneal edema resulting in poor visualization of the retina.

REFERENCES 1. Parel JM, Parrish RK, Nose I. An intraoperative intraocular pressure monitor. Ophthalmic Surg. 1987;18(5):371-4. 2. Witherspoon CD, Morris RE, Goggans WE. Automated regulation of fluid infusion pressure during vitrectomy. Arch Ophthalmol. 1986;104(10):1551. 3. Moorehead LC, Armeniades CD. The pressure-controlled infusion system: a new instrument for closed-system surgery. Ophthalmic Surg. 1988;19(4):282-8. 4. Charles S, Katz A, Wood B. Vitreous Microsurgery, 3rd edition. Philadelphia: Lippincott Williams and Wilkins; 2002. pp. 28-9. 5. Corcóstegui B, Adán A, García-Arumí, et al. Cirugía vitreoretiniana, indicaciones y técnicas. Madrid. Tecnimedia editorial; 1999. pp. 50-2.

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5.5  INFUSION DEVICES SYSTEMS TWENTY-GAUGE INCISIONS Opening the Conjunctiva Infusion cannulas are connected to the infusion line. They are used to introduce physiological saline, air and sometimes silicone oil into the globe.1 The lengths available are: 2.5 mm, 4 mm and 6 mm; the 4 mm cannula being the most widely used (Fig. 1). The 6 mm cannula is used when we know there is dense or fibrous tissue in the periphery of the retina, to make sure we have reached the eye interior. The cannula is then used to instill fluid in the vitreous space. We routinely use the 4 mm probe, making sure the beveled tip faces upwards to avoid touching the crystalline lens in a phakic eye. It should always be checked that the infusion cannula has been effectively introduced in the vitreous space otherwise opening the infusion line could provoke detachment of the choroid, precluding surgery. Also available are infusion cannulas fitted with fiber optics (Fig. 2) for supplementary illumination when performing bimanual surgery.2 To avoid extrusion of the infusion cannula during surgery, the tube is sutured to the sclera, allowing the surgeon to work with indentation. If small bubbles enter through the sclerotomy during surgery, this means the cannula has not been properly fixed and requires resuturing. There are several self-retaining cannulas that do not need to be sutured3-5 yet allow good perfusion control (Fig. 3). When instruments do not need to be introduced into the globe, such as when reviewing the periphery or tightening a scleral buckle at the end of surgery, we use 20-gauge plugs to close the sclerotomies and avoid intraocular tissue incarceration in the case of a high intraocular pressure (IOP) provoked by the surgical maneuvers (Fig. 4A). When using valved trocars, indentation is possible without the need for plugs (Fig. 4B).

Figure 1  Infusion cannulas of lengths 2.5 mm, 4 mm and 6 mm. The 4 mm cannula sutured to the sclera is used most often

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Figure 2  Dorc’s illuminating infusion cannula. This cannula allows the control of intraocular pressure while diffusely illuminating the fundus

Figure 3  Dorc’s sutureless infusion cannula. The retainer at the base of the cannula keeps it in place during surgery

A

B

Figures 4A and B  (A) Scleral plugs and plug forceps supplied by Alcon; (B) Valved trocars maintain the stability of the globe by preventing the leakage of saline

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Figure 5  A counter incision creates a self-sealing valve against intraocular pressure Source: Reproduced with permission from Theelen T, Verbeek AM, Tilanus MA, et al. A novel technique for self-sealing, wedge-shaped pars plana sclerotomies and its features in ultrasound biomicroscopy and clinical outcome. Am J Ophthalmol. 2003;136(6):1085-92

TWENTY-GAUGE TRANSCONJUNCTIVAL VITRECTOMY It is currently possible to perform a 20° transconjunctival vitrectomy6,7 by introducing the massive vitreous retractor blade perpendicularly to the limbus with a 15° orientation to the sclera. Penetration should be conducted at right angles to the sclera; introducing the infusion cannula first and leaving it without sutures. At the end of surgery, the eye should remain filled with air to avoid a large drop in IOP. If after checking the incisions, there is continued air leakage, a counter incision creates a self-sealing valve for a nonleaking sutureless sclerotomy8 (Fig. 5). Many of the trocars available are valved, so we do not need plugs for indentation. Twenty-three, 25- and 27-gauge transconjunctival vitrectomies are dealt within the chapter on microincisions.

REFERENCES 1. Charles S, Katz A, Wood B. Vitreous Microsurgery, 3rd edition. Philadelphia: Lippincott Williams and Wilkins; 2002. pp. 26. 2. Zinn KM, Grinblat A, Katzin HM, et al. A new endoillumination infusion cannula for pars plana vitrectomy. Ophthalmic Surg. 1980;11(12):850-5. 3. Mason G, Sullivan JM, Olk RJ. A sutureless self-retaining infusion cannula for pars plana vitrectomy. Am J Ophthalmol. 1990;110(5):577-8. 4. Hilton GF. A sutureless self-retaining infusion cannula for pars plana vitrectomy. Am J Ophthalmol. 1985;99(5):612. 5. Rahman R, Rosen PH, Riddell C, et al. Self-sealing sclerotomies for sutureless pars plana vitrectomy. Ophthalmic Surg Lasers. 2000;31(6):462-6. 6. Stanescu-Segall D, Sebag M, Jackson T, et al. Modified 20-gauge transconjunctival pars plana vitrectomy. Retina. 2011;31(5):982-7. 7. Lafetá AP, Claes C. Twenty-gauge transconjunctival sutureless vitrectomy trocar system. Retina. 2007;27(8):1136-41. 8. Theelen T, Verbeek AM, Tilanus MA, et al. A novel technique for self-sealing, wedge-shaped pars plana sclerotomies and its features in ultrasound biomicroscopy and clinical outcome. Am J Ophthalmol. 2003;136(6):1085-92.

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5.6  SUCTION AND CUTTER SYSTEMS INTRODUCTION In the early days of vitreoretinal surgery, probes capable of cutting, aspiration, infusion and even endoillumination were used.1,2 These multipurpose instruments required incisions as large as 3.5 mm, which led to the development of smaller instruments carrying out the functions of aspiration and cutting separate from infusion and illumination3-5 that could be introduced through 0.9 mm incisions. These new instruments greatly facilitated globe rotation, bimanual surgery maneuvers and have made three-port vitrectomy the procedure of choice. Intraocular aspiration can be achieved either actively through the use of aspiration pumps—traditionally a Venturi effect pump and more recently peristaltic pumps—or passively, using instruments in which suction is generated through the difference in intra and extraocular pressure.

ACTIVE ASPIRATION The basic functions of the vitrectomy probe are aspiration and cutting. These functions are performed with the help of the vitrectomy machine, which incorporates an aspiration pump and a pneumatic or electric cutting device. Today, vitrectomy machines incorporate both Venturi and peristaltic pumps, which the surgeon can easily select during surgery using the foot pedal. The Venturi pump creates a vacuum in a closed, rigid chamber. In this system, a compressed gas passes through a conduit of increasing diameter connected to a chamber, which in turn, is linked to the aspiration tube. This flow through the conduit generates a vacuum in the chamber and the vacuum exerts a negative or suction pressure in the aspiration tube (Fig. 1). The vacuum is regulated by varying the amount of compressed gas producing the vacuum in the chamber. This system has a quick response time for starting and stopping suction such that the vitreous can be easily extracted. Peristaltic pumps produce a vacuum as the roller rotates on the aspiration tubes, which therefore need to have some degree of elasticity (Fig. 2). The flow rate or aspiration speed is provided in ml/min and is directly proportional to the pump rotation speed; the greater the speed the higher the flow rate. The main feature of the peristaltic pump is that we can separate flow (aspiration speed) from vacuum (level of aspiration or negative suction pressure produced when the aspiration system is occluded). For a peripheral vitrectomy, we use a flow rate under 10 ml/min and a high vacuum to approach the periphery of the retina and selectively eliminate the vitreous without the risk of damaging the retina. This is possible because as we occlude the aspirator, the vacuum is very slowly generated such that the vitreous alone, and not the retina, is pulled, allowing selective cutting of the vitreous.

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Figure 1  Venturi pump. Flow rate and vacuum power cannot be separated, providing a rapid response time while aspirating

Figure 2  Peristaltic pumps with independent flow and vacuum functions so that we can work with low flow rates close to the retina

Most surgeons use both types of pump: the Venturi for central vitrectomy and the peristaltic pump for peripheral vitrectomy or when working close to the retina. Both pumps are also used in combined phacoemulsification-vitrectomy procedures (Figs 3A and B). With the traditional vitreotome, the surgeons controlled aspiration and cutting devices through the use of foot pedals. By depressing the pedal to a greater or lesser extent (linear control), the intensity of aspiration could be

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A

B

Figures 3A and B  Dorc vitreotome supplied with both Venturi and peristaltic pumps for use at the anterior and posterior poles

instantly adjusted, although the same could not be done for the cutting function, since once the cutter was connected it worked at the same speed. In today’s vitreotomes, both these functions can be linearly controlled. We use the Accurus vitreotome, which does not have a peristaltic pump, but has a dual system that allows some flow control (Fig. 4). This machine has three vitrectomy systems for the following purposes: ƒƒ Linear vitrectomy such that we can linearly control aspiration but the cutting speed is preset. Thus, if using high cutting speeds and low aspiration, the suction is low. As we lower the cutting speed, suction power increases especially if we increase the aspiration intensity. Cutting speeds of 600–800 cuts per minute and maximum vacuum pressures of 125–150 mm Hg can

Figure 4  Diagram showing the flow control provided by the Accurus vitreotome using the dual vitrectomy mode. As the pedal is lowered, vacuum power increases and cutting rate diminishes such that the suction power of the probe increases. As the foot pedal is released, the vacuum decreases and cutting rate increases providing less flow and suction power for use, particularly, in the retinal periphery

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82 be applied. If we use high-speed probes, the vacuum pressure has to be increased ƒƒ Momentary vitrectomy (linear vacuum and cutting speed on demand), whereby aspiration is linearly controlled and when needed, we can introduce a preset cutting rate from 1 cut per minute ƒƒ Dual vitrectomy (dual dynamic drive) allows simultaneous regulation of cutting speed and vacuum pressure using the pedal within independent limits. Flow control using the Accurus vitreotome is managed as follows: ƒƒ Flow increased by pressing the pedal –– Vacuum increases and cutting rate diminishes ƒƒ Flow reduced by releasing the pedal –– Vacuum decreases and cutting rate increases. We normally use the dual system since it is highly responsive: when we need more suction power, we press the pedal and when we do not want suction, we lift the foot off the pedal (Fig. 5). To segment the fibrous membranes in proliferative retinopathies, we use the vitrectomy probe in the momentary mode (Fig. 6) to attract tissue to the vitrectomy port, and then introduce the cutting function using the pedal to remove slightly raised membranes. A further active aspiration method is the extrusion cannula system, which is independent of the machine’s aspiration system.6 Hence, we can connect a silicone-tipped cannula for linear foot-controlled suction to lift a hyaloid membrane, aspirate subretinal fluid or for fluid/air exchange (Fig. 7).

Figure 5  3D or dual system in which the vacuum needs to be preprogrammed for treadle start, full treadle and cuts per minute. In this way, the start of the pedal trajectory provides a low vacuum intensity and high cutting rate for low suction and greater safety, while the end of the pedal push will give us high vacuum and a lower cutting speed for greater efficiency

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83

Figure 6  Momentary vitrectomy system in which the aspiration threshold and number of cuts per minute are programmed. Vacuum power is linear, while the cutting rate is fixed and activated when required using the pedal

Figure 7  Extrusion system independent of the vitrectomy probe. Using this system a silicone tipped cannula can be connected for linear suction power until a preset maximum

PASSIVE ASPIRATION Passive aspiration, involving the use of a silicone-tipped cannula to sweep the retina without damaging it, is based on the intra and extraocular pressure difference.7 Since the intraocular pressure (IOP) is greater than the pressure outside the eye, any fluid or blood will travel up the cannula. The higher the IOP, the greater will be the cannula’s power of suction (Fig. 8). This type of probe is used to clean away blood remnants on the retina, identify membranes or their remains when we have finished dissecting and to aspirate subretinal

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Figure 8  The exit of perflurocarbon liquid is the result of the difference between intraocular pressure and the lower atmospheric pressure outside the eye. The higher the intraocular pressure, the greater the suction power

Figure 9  Dorc’s backflush probe allowing passive aspiration and reflux. The tip is made of silicone and has cuts to avoid tissue incarceration. This device can be connected to the equipment’s active aspiration drive

fluid. Backflush systems can be used for passive aspiration. These probes allow fingertip-controlled backflush (Fig. 9).

VITRECTOMY PROBES Cutting can be achieved by a guillotine pneumatic mechanism that can be activated by air or liquid nitrogen. Alternatively, the use of an electric mechanism provides a rotary cutting action reaching cutting speeds of 2,500 cuts per minute, requiring an increase in aspiration power. The vitreotome should have a backflush system in the aspiration line. Current pneumatic vitreotomes offer high cutting speeds of up to 2,500 cuts per

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85 minute, which together with appropriate suction levels serve to safely sweep the anterior vitreous. High-speed vitreotomes exert less traction on the vitreous and are safer to use. Using the linear vitrectomy system with a preset cutting speed, the suction pressures and cutting rates successfully used by us are: ƒƒ Central vitreous: Aspiration 150–200 mm Hg and cutting speed of 600 cuts per minute ƒƒ Peripheral vitreous: aspiration 100 mm Hg and cutting rate of 800–1,200 cuts per minute. Cutting can be undertaken without suction. If we need to cut a fibrous posterior capsule, the cutting speed is reduced and aspiration power is increased, with care taken to avoid traction on the retina. The probe we prefer is the Accurus 2500, which is very ergonomic. This vertical guillotine has a distal aspiration tip and a 32 mm probe and works well in long eyes. Cutting is controlled by a microprocessor (Figs 10A and B). We always work following the configuration of the vitreous. This means making circular movements around the globe’s 360°, trying to avoid traction to prevent tears. Below we describe two new high-speed cutting vitrectomy machines.

Constellation Vision System This machine incorporates new Ultravit© probe for a high cutting rate and good control of the duty cycle by modifying the probe opening time irrespective of cutting or vacuum functions, thus controlling flow. It also has a new IOP control system with a vented gas forced infusion device integrated in the cassette offering immediate response to pressure changes.

A

B

Figures 10A and B  (A) Detailed image of the Accurus 2500 vitrectomy probe showing the guillotine and its closeness to the probe tip; (B) Its concave shape is designed for grasping between the index finger and thumb

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86 Its two xenon light sources comprise 20-, 23- and 25-gauge optic fibers, featuring a new probe for retractable illuminated laser functions. The Constellation system also incorporates a new 532 nm green-emitting laser. For combined phacovitrectomy procedures, it also features OZil Intelligent Phaco, a phacofragmentation handpiece, and pneumatic forceps and scissors, which can be adjusted with the foot pedal to work in simple or multicut mode. Its injection/extraction pump works with 20- and 23-gauge cannulas. The diathermy module with fixed and linear functions allows for selective controlled diathermy. Another of the Consellation’s features is that from the main menu C3F8 and SF6 gas bottles can be refilled at the desired concentration. In addition, an automatic fluid/air exchange valve, controlled using the foot pedal, obviates the need for a three-way valve. The new vitrectomy probes and duty cycle control merit further attention. Ultravit© probes are pneumatically driven. They are available in calibers of 20-, 23- and 25-gauge, and all attain cutting speeds of up to 5,000 cuts per minute, reducing traction on the ocular tissue. The open position of the probe is optimized in the most distal zone so that the surgeon can work close to the retina using the vitrectomy modes: 3D, linear or momentary. With the traditional pneumatic vitrectomy probes, the guillotine is advanced via air pulses. The return path of the guillotine is passively achieved by means of a spring. The new probes are fitted with two pneumatic lines that provide air pulses, actively controlled by the machine’s microprocessor. This means the guillotine may be advanced and retracted offering the surgeon effective duty cycle control (Figs 11A and B).

A

B

Figures 11A and B  (A) Traditional pneumatic vitrectomy probe; (B) New probe Ultravit©

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Duty Cycle Control Till now, the surgeon could only control the vacuum and cutting frequency. The new technology introduces a new variable, the duty cycle, which indicates the proportion of time the vitrectomy port is open or closed.8 This function is independent of the desired cutting speed or preselected vacuum. Three duty cycles are available: core, 50/50 and shave (Fig. 12). ƒƒ Core: this indicates maximum opening time of the vitrectomy port and is used when seeking greater efficiency and flow rates ƒƒ 50/50: the port remains open half of the time and closed the remaining half of the time ƒƒ Shave: port opening is minimized for the gentle extraction of tissues, generally at the periphery where lower flow rates are preferred to minimize pull. For a good vitrectomy, we should try not to pull the vitreous with the probe, cutting it into small pieces while maintaining flow as low as possible. Using the new probes, we can cut the vitreous into small fragments and select the appropriate duty cycle to carefully control the flow. It should be remembered that electric probes work at a constant duty cycle, thus the open/close port time proportion is the same such that flow will be constant when we work at high or low cutting speed; the only factor that varies is fragment size, which will be smaller for higher cutting speeds9 (Table 1). Our experience with the Constellation system and new Ultravit© probe is that the system allows for a better controlled vitrectomy with improved adjustment of flow, or traction on tissue. The instrument is especially effective when working at the periphery since using the shave mode we can almost “caress” the retina without harming it.

Figure 12  Constellation vision system. Duty cycle control: Core, 50/50, Shave

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88 TABLE 1 Benefits and drawbacks of the different vitrectomy modes Small vitreous fragment

Large vitreous fragment

Benefits

Low force and tissue deformation

Force exerted over a large surface area

Drawbacks

Force spread across a small High force and tissue deformation surface area

Stellaris PC Vision Enhancement System This new platform introduces new illumination sources with the choice of several filters when we use the xenon light. This equipment is also good for small incision (1.8 mm) combined phacovitrectomy.10 Its pneumatic probes with optimized duty cycles determine an open port at least 50% of the time even at a cutting speed of 5,000 cuts per minute. These probes can thus work at ultra-rapid cutting speeds yet at a duty cycle that enables the effective elimination of vitreous. Because of the high cutting rate, vitreous pieces are smaller and behave more like a liquid, facilitating their removal without traction. We would highlight the following features: a new programmable wireless foot pedal, and two independent double xenon and mercury lamps with three color filters for the xenon light—yellow, green and amber—which the surgeon intercalates using the foot pedal. The green filter is absorbed by red pigment and provides a darker view of the fundus. This filter is considered best for peeling membranes. The yellow filter is absorbed by the xanthophyll pigments of the macula providing a warm color when we use a blue dye. Amber is considered the safest color filter for unstained eye tissues; it is absorbed by blue dye and is defined as the best filter to visualize the peripheral retina. The mercury vapor lamp generates brilliant light for prolonged procedures. The angle of vision has been improved with the new wide-field illumination probes.

REFERENCES 1. Machemer R, Parel JM, Buettner H. A new concept for vitreous surgery. I. Instrumentation. Am J Ophthalmol. 1972;73(1):1-7. 2. O’Malley C, Heintz RM. Vitrectomy via the pars plana—a new instrument system. Trans Pac Coast Otoophthalmol Soc Annu Meet. 1972;53:121-37. 3. Peyman GA. Miniaturization of the vitrophage: vitrectomy instrument. Can J Ophthalmol. 1980;15(1):49-50. 4. Zinn KM, Grinblat A, Katzin HM, et al. An improved endoillumination probe for pars plana vitrectomy. Ophthalmic Surg. 1980;11(10):698-700. 5. Rappazzo JA, Michels RG. New system of intraocular instruments. I. Guillotine intraocular forceps. Arch Ophthalmol. 1983;101(5):814-5.

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89 6. Charles S, Katz A, Wood B. Vitreous Microsurgery, 3rd edition. Philadelphia: Lippincott Williams and Wilkins; 2002. pp. 94-5. 7. Peyman GA, Diamond J. A new variable suction system with finger-tip control. Can J Ophthalmol. 1986;21(6):225-6. 8. Kirk H, Packo MD. High speed cutting and duty cycle control. Retina Today Supplement. 2009;3-6. 9. Magalhães O, Maia M, Rodriques EB, et al. Perspective on fluid and solid dynamics in different pars plana vitrectomy systems. Am J Ophthamol. 2011;151(3):401-5. 10. Awh C, Tadayoni R. Stellaris PC: improved illumination and visualization for retina surgery. Retina Today Supplement. 2011;3-6.

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5.7 DIATHERMY INTRODUCTION The control of bleeding is essential during vitreoretinal surgery. This problem is most common in eyes with proliferative diabetic retinopathy or after penetrating eye wounds. Bleeding is usually controlled during the dissection and removal of abnormal tissue by increasing the height of the irrigation bottle or the positive pressure pump to raise intraocular pressure (IOP).1,2 However, entire bleeding should cease before the end of the surgery and this is verified by decreasing the IOP to check if bleeding reappears. Focal points of hemorrhage are treated with diathermy or photocoagulation. In vitreoretinal surgery, an efficient hemostasis system is required, since bleeding in the vitreous cavity will darken the viewing field and may induce postoperative preretinal cell proliferation. In effect, all modern vitrectomy machines have an integrated diathermy system. Diathermy is used to control bleeding, to constrict fibrovascular tissue or create a drainage retinotomy, marking the retinotomy zone with the endodiathermy device.3 Diathermy may be applied using a unipolar or bipolar system. The bipolar method is preferable since it minimizes the diverted current. If unipolar diathermy is used to close to the optic nerve, the energy could be transmitted to the nerve causing optical atrophy and permanent blindness.4,5 Some years ago, bipolar bimanual diathermy was used whereby electrodes were connected to the instruments whose tips worked as electrodes to coagulate fibrovascular tissue. With this system, it is not necessary to withdraw the instruments to coagulate blood vessels although the method is at present hardly used. The method mostly used is the bipolar unimanual system, in which diathermy is applied with a single probe that has two electrodes with adequate insulation (coaxial bipolar diathermy). These are the classic scleral erasers and fine point endodiathermy pencils. Forceps type diathermy tips are excellent for control of bleeding on the sclera, conjunctiva and Tenon’s capsule (Fig. 1). Diathermy is now done using 23 gauge instruments (Fig. 2). Bipolar coagulation instruments with aspiration and backflush functions enable the surgeon to aspirate blood and identify the bleeding vessel with the possibility of backflush if incarceration occurs (Fig. 3). Another useful instrument is the handpiece for illuminated, unimanual, bipolar diathermy that can be used with the vitreotome as an aspirating line (Fig. 4). As already mentioned, some tissue manipulators are equipped with aspiration, diathermy and endoillumination systems.6 These are especially useful to remove fibrovascular proliferations, mainly in diabetic retinopathy (Fig. 5).

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Figure 1  Diathermy forceps and erasers

Figure 2  Dorc’s 23-gauge diathermy instrument

Figure 3  Medtronic’s cannulas for bipolar diathermy with active/passive aspiration, backflush and extrusion functions

Figure 4  Illuminating diathermy probe for selective coagulation of a bleeding point

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Figure 5  Tissue manipulator incorporating three functions (illumination, aspiration and coagulation) in a single instrument

REFERENCES 1. Klein RM. Hemorrhage of major branch retinal artery during vitrectomy. Retina. 1986;6(2):123-4. 2. de Bustros S. Intraoperative control of hemorrhage in penetrating ocular injuries. Retina. 1990;10 Suppl 1:S55-8. 3. Fisher YL, Sorenson JA. Retinal tear localization following fluid-gas exchange during pars plana vitreoretinal surgery. Am J Ophthalmol. 1984;97(3):390. 4. Parel JM, Machemer R, O`Grady GE, et al. Intraocular diathermy coagulation. Graefes Arch Clin Exp Ophthalmol. 1983;221(1):31-4. 5. Machemer R. Transvitreal radiofrequency diathermy. Am J Ophthalmol. 1977; 83(2):282. 6. Awh CC, Rader RS, Walsh AC, et al. A fiberoptic pick-manipulator for vitreoretinal surgery. Arch Ophthalmol. 1994;112(6):853-4.

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5.8 RETINOPEXY INTRODUCTION All retinal tears should be treated with some form of retinopexy, since it is impossible to predict when a tear will lead to retinal detachment and also because of the relative safety of retinopexy. For cryocoagulation, a probe is applied to the scleral wall to freeze the endo-ocular tissues and induce chorioretinal scars. On the down side, we know that cryotherapy causes migration of pigment epithelium cells promoting their proliferation, such that it is best to limit its use to cases where it is strictly necessary. The cryotherapy probe is an excellent tool for indenting the globe and we use it to revise the retinal periphery at the end of surgery. If we find any small tears, these can be sealed with cryotherapy directly controlled under the microscope. We never apply cryotherapy without control at the end of surgery in a zone posterior to the sclerotomy (Fig. 1). Another situation in which we could use cryotherapy would be to complete panretinal coagulation in the peripheral retina in cases of active proliferative diabetic retinopathy, particularly at sclerotomy sites, reducing the risk of proliferation, which sometimes gives rise to recurrent hemorrhage. In this case, we always undertake cryotherapy after completing the vitrectomy with the retina attached and with direct control under the microscope. The use of endoocular cryoprobes is reserved for cases of atrophy of the pigment epithelium or albino patients.1,2 Our method of choice for retinopexy is endophotocoagulation in the periphery with the cryotherapy probe, which achieves excellent indentation and provides good vision of the retinal periphery. To do this, we often indent with one hand and use the laser probe with illumination on the other hand to treat zones anterior to the retina with relative comfort (Figs 2A and B).

LASER ENDOPHOTOCOAGULATION Endophotocoagulation is performed using a probe introduced through a sclerotomy. The first endocoagulator was a portable xenon arc.3 The endoprobe

Figure 1  This is the cryoprobe we use for small holes as a method of pexis and especially to indent the retinal periphery

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A

B

Figures 2A and B  (A) Peripheral indentation using the cryoprobe; (B) Endophotocoagulation with an illuminated laser probe

had to be positioned 0.5 mm from the retina; the light emitted was multicolored and was absorbed by all retinal pigments, which is why this type of laser is not used nowadays. The light from the laser is unidirectional and is transmitted through an optical fiber4 allowing photocoagulation some distance from the retina. The size of the laser spot is 600–1000 μm depending on the distance from the probe tip to the retinal surface. If we want to cause a small burn, we should bring the probe closer to the retina and reduce the power selected. Conversely for more extensive impacts, we need to move away from the retina. The type of impact produced also depends on the position of the probe with respect to the retina. Thus, if we place the probe perpendicular to the retina we will achieve a rounded impact, but if the orientation is oblique, the impact will be oval, especially at the periphery where the probe makes a tangent with the retinal surface. This slanted approach can be avoided using curved probes, which are better at reaching peripheral zones (Fig. 3). The endolaser is used to treat retinal tears, for panretinal photocoagulation in patients with diabetic retinopathy, occlusive venous disease, hemoglobin disorder or retinal telangiectasia.5 We can also use the endolaser with light to treat a bleeding vessel6 (Fig. 4). For extensive bleeding, we will need to use an aspiration probe or the vitrectomy probe to aspirate the blood followed by accurate coagulation. This will enable us to keep one hand free for aspirating and observing where the blood is coming from or for peripheral indentation as indicated previously. We can also endophotocoagulate ciliary processes in cases of glaucoma of difficult control, aided by scleral indentation.7,8 Some laser probes have an aspiration port to remove residual fluids and completely dry the retina before photocoagulation (Fig. 5). The lasers, we use to achieve photocoagulation in an eye, are filled with infusion fluid, air or gas, liquid perfluorocarbon or silicone oil. In eyes filled with air or gas, the effect of the laser is intensified and the risk of provoking

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Figure 3  Synergetic laser probe allowing a straight or curved approach

Figure 4  This illuminating probe allows laser treatment with one hand and indentation with the other

Figure 5  Laser probe capable of aspiration to dry the retina before photocoagulation

hemorrhage or tears is increased. Intense laser treatment applied under any type of gas or fluid can cause retinal tearing, but this is most likely to occur in eyes filled with air or gas. In general, it is best to use lower power impacts for a longer exposure time to avoid explosive effects on the retina. Currently, the lasers used are argon, infrared diode, green diode and yellow lasers.

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Argon Laser This laser emits blue-green light (440–550 nm) or green light alone. The light is absorbed well by hemoglobin and melanin. The wound produced is coneshaped with its apex in the blood vessels and base in the choriocapillaris.9,10 Its drawbacks are: ƒƒ It is absorbed by hemoglobin and will thus destroy the retina in hemorrhagic retinopathy ƒƒ Poor transmission arises when there are opacities in the media along with absorption by the vitreous and crystalline lens of some of the radiation.

Diode Laser This laser uses gallium, aluminum and arsenic semiconductor crystals which upon excitation produce radiation close to the infrared range 790–950 nm (peak at 810 nm). This solid state laser has the following advantages: it is small, does not require water refrigeration since it has no tube, needs no special electrical installation and can be fitted to a slit lamp, binocular ophthalmoscope, endo-ocular probe or scleral probe (Fig. 6). This laser can coagulate through hemorrhage. It produces occlusion of choriocapillaris and large vessels. It has a red guiding light. Diode lasers emit at wavelengths close to the infrared range and produce deeper burns.

Green Diode Laser This is the most recently developed laser. It has the same applications and acts similar to the argon laser with the advantages of the diode. The radiations it emits are better absorbed by the pigment epithelium and hemoglobin than argon (Fig. 7). Despite emitting green light, it produces a guiding red 670 nm beam.

Figure 6  The 810 nm diode laser achieves high penetration endophotocoagulation and has a red guiding light

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Figure 7  The 532 nm diode laser emits in the green spectrum but has a red guide light and shows optimal hemoglobin and oxyhemoglobin absorption

Yellow Laser Recently a yellow 577 nm laser has been introduced, which causes less energy dispersion to adjacent tissues. It is a solid state laser of power 2,000 mW. Probe is available for endo-ocular laser treatment (Fig. 8). This laser also has a micropulse mode for photocoagulation in the macular zone, where it is not absorbed by xanthophyll and the wound is limited to the pigmentary epithelium alone11 (Fig. 9). This wavelength has been incorporated into the Pascal laser for routine retinal treatment using the different grids available. All these lasers require a filter to avoid glare and possible retinal damage to the surgeon and assistants. This filter should be positioned under the eyepieces for protection during photocoagulation.

Figure 8  Yellow 577 nm solid states, high reliability laser with a power of 2,000 mW for endophotocoagulation, featuring a micropulse mode

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Figure 9  Absorption at different wavelengths

REFERENCES 1. Shea M. A microprobe for intraocular cryosurgery. Can J Ophthalmol. 1967; 2(3):163-8. 2. Bradbury MJ, Fung WE. A new 20-gauge intravitreal cryoprobe. Am J Ophthalmol. 1980;90(3):424-5. 3. O´Malley P. Portable xenon arc light coagulator. Br J Ophthalmol. 1973; 57(12):935-44. 4. Landers MB, Trese MT, Stefansson E, et al. Argon laser intraocular photocoagulation. Ophthalmology. 1982;89(7):785-8. 5. Charles S. Endophotocoagulation. Retina. 1981;1(2):117-20. 6. Awh CC, Schallen EH, de Juan E. An illuminating laser probe for vitreoretinal surgery. Arch Ophthalmol. 1994;112(4):553-4. 7. Lim JI, Lynn M, Capone A, et al. Ciliary body endophotocoagulation during pars plana vitrectomy in eyes with vitreoretinal disorders and concomitant uncontrolled glaucoma. Ophthalmology. 1996;103(7):1041-6. 8. Sears JE, Capone A, Aaberg TM, et al. Ciliary body endophotocoagulation during pars plana vitrectomy for pediatric patients with vitreoretinal disorders and glaucoma. Am J Ophthalmol. 1998;126(5):723-5. 9. Acheson RW, Capon M, Cooling RJ, et al. Intraocular argon laser photocoagulation. Eye (Lond). 1987;1(Pt 1):97-105. 10. Karlin DB. Intravitreal argon and carbon dioxide laser, and xenon arc photo­ coagulation in vitreoretinal surgery. Graefes Arch Clin Exp Ophthalmol. 1986; 224(3):221-5. 11. Ohkoshi K, Yamaguchi T. Subthreshold micropulse diode laser photocoagulation for diabetic macular edema in Japanese patients. Am J Ophthalmol. 2010;149(1):133-9.

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5.9 PHACOEMULSIFICATION INTRODUCTION Phacoemulsification is the current technique of choice for cataract surgery. It may also be used when a candidate, for vitreoretinal surgery, has an opacity preventing good visualization of the posterior pole. In such cases, combined cataract/vitreoretinal surgery is recommended.1-12 It is not recommended to perform two separate surgeries, since besides increasing costs, more inflammation is produced. All vitrectomy machines are equipped with an ultrasound system for cataract removal through a clear corneal incision. Surgery can be performed by a vitreoretinal surgeon trained for this procedure or an anterior pole surgeon. The use of phacoemulsification to extract the cataract, means the intraocular lens (IOL) haptics can be placed in the capsular bag, reducing contact between the IOL and the uveal tissue thus preventing rupture of the blood-aqueous barrier, which in turn, diminishes the inflammatory response.13 Implanting the IOL inside the bag improves centering of the lens and reduces pigment dispersion induced by mechanical rubbing of the haptics against the posterior pigment epithelium of the iris if the intraocular pressure has to be implanted in the sulcus.14 We routinely undertake combined phacoemulsification/vitrectomy surgery. Surgery is started by placing the infusion port 3.5 mm from the limbus, using the normal clear cornea approach. The crystalline lens nucleus is bimanually fractured to reduce the ultrasonography time and we always undertake IOL placement at the end of the vitreoretinal surgery procedure. This allows us good access to the posterior pole and periphery, permitting better management of any complications that could arise during surgery such as tears, deinsertions, bleeding, etc. The surgeon can even decide not to implant the IOL and remove the capsule at the end of the surgery. When scleral indentation is indicated, the scleral buckle is fixed before positioning the port for cataract surgery. This maneuver would otherwise be difficult and carries the risk of intraocular complications due to handling of the muscles. Our indications for combined phacovitrectomy surgery are cataracts of hardness grade II or more while in the case of a clear crystalline lens or hardness grade I cataract, the patient is subjected to a pars plana lensectomy. Combined surgery is always preferred to separate surgeries. We can also use the phacoemulsifier hand piece without irrigation to extract a crystalline lens luxated to the vitreous with grade III or IV cataract (Figs 1A and B). The following are the prerequisites for this procedure: ƒƒ There should be no corneal edema from previous surgery as edema prevents good visualization of the posterior retina, particularly of the periphery,

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A

B

Figures 1A and B  (A) Phaco tip used to retrieve a crystalline lens luxated to the vitreous; (B) Lifting the middle of the vitreous cavity to proceed with the emulsification process

increasing the risk of complications. Moreover, if there is corneal edema, surgery could be cut short by the appearance of striate keratopathy. It is therefore always advisable to wait for any corneal edema to resolve ƒƒ The vitrectomy should be carefully undertaken to remove as much peripheral vitreous as possible, thus avoiding interference with the phacoe­ mulsification tip ƒƒ If not already detached, removal of the posterior hyaloid should be done. To do this, it helps if we observe how the remains of the crystalline lens move: if it seems they are attached, this indicates the hyaloid is still connected but if the remnants move freely, this will tell us the hyaloid membrane is detached ƒƒ Fluid dynamics should be slow, increasing the infusion pressure to avoid prolapses at the start of aspiration ƒƒ We recommend the pulse mode to keep the crystalline lens adhered to the tip ƒƒ Always keep an eye on the phacoemulsification probe tip ƒƒ Bear in mind that phaco tips are short and it is difficult to reach the posterior pole ƒƒ Finally, we should remember that the phacoemulsifier is very efficient inside the globe but can be very dangerous if not adequately used. For hard nuclei, we use Alcon’s Legacy/Infinity system, which incorporates a peristaltic pump, with a microtip needle angled at 0–15° without irrigation in pulse mode, varying the power and vacuum as required, starting with low levels and gradually increasing these until they become efficient.

REFERENCES 1. Nawrocki J, Cisiecki S. Combined surgery, phacoemulsification, implantation of intraocular lens and pars plana vitrectomy. Klin Oczna. 2004;106(4-5):596-604. 2. Lahey JM, Francis RR, Kearney JJ, et al. Combining phacoemulsification and vitrectomy in patients with proliferative diabetic retinopathy. Curr Opin Ophthalmol. 2004;15(3):192-6.

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101 3. Pollack A, Landa G, Kleinman G, et al. Results of combined surgery by phacoemulsification and vitrectomy. Isr Med Assoc J. 2004;6(3):143-6. 4. Lahey JM, Francis RR, Kearney JJ. Combining phacoemulsification with pars plana vitrectomy in patients with proliferative diabetic retinopathy: a series of 223 cases. Ophthalmology. 2003;110(7):1335-9. 5. Heiligenhaus A, Holtkamp A, Koch J, et al. Combined phacoemulsification and pars plana vitrectomy: clear corneal versus scleral incisions: prospective randomized multicenter study. J Cataract Refract Surg. 2003;29(6):1106-12. 6. Lam DS, Young AL, Rao SK, et al. Combined phacoemulsification, pars plana vitrectomy, and foldable intraocular lens implantation. J Cataract Refract Surg. 2003;29(6):1064-9. 7. Demetriades AM, Gottsch JD, Thomsen R, et al. Combined phacoemulsification, intraocular lens implantation, and vitrectomy for eyes with coexisting cataract and vitreoretinal pathology. Am J Ophthalmol. 2003;135(3):291-6. 8. Lahey JM, Francis RR, Fong DS, et al. Combining phacoemulsification with vitrectomy for treatment of macular holes. Br J Ophthalmol. 2002;86(8):876-8. 9. Lam DS, Rao SK, Chan WM, et al. Combined phacoemulsification and pars plana vitrectomy. J Cataract Refract Surg. 1999;25(10):1309-11. 10. Scharwey K, Pavlovic S, Jacobi KW. Combined clear corneal phacoemulsification, vitreoretinal surgery, and intraocular lens implantation. J Cataract Refract Surg. 1999;25(5):693-8. 11. Senn P, Schipper I, Perren B. Combined pars plana vitrectomy, phacoemulsification, and intraocular lens implantation in the capsular bag: a comparison to vitrectomy and subsequent cataract surgery as a two-step procedure. Ophthalmic Surg Lasers. 1995;26(5):420-8. 12. Koenig SB, Mieler WF, Han DP, et al. Combined phacoemulsification, pars plana vitrectomy and posterior chamber intraocular lens insertion. Arch Ophthalmol. 1992;110(8):1101-4. 13. Kokame GT, Flynn HW, Blankenship GW. Posterior chamber intraocular lens implantation during diabetic pars plana vitrectomy. Ophthalmology. 1989; 96(5):603-10. 14. Mamalis N, Teske MP, Kreisler KR, et al. Phacoemulsification combined with pars plana vitrectomy. Ophthalmic Surg. 1991;22(4):194-8.

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5.10  ULTRASONIC FRAGMENTATION INTRODUCTION Girard was amongst the first to propose the use of ultrasound in vitrectomy surgery and developed an instrument with a 0.9 mm diameter cannula capable of undergoing between 20,000 vibrations per second and 40,000 vibrations per second as well as aspirating.1 Infusion was conducted independently through another sclerotomy. This system serves to emulsify the crystalline lens2 through the pars plana introducing a second infusion cannula in the crystalline, and through ultrasound and aspiration, the lens can be removed, preserving the anterior capsule intact until the end of surgery. We can also use this device to emulsify fragments of crystalline lens in the vitreous.3 This requires a good central and peripheral vitrectomy before we can introduce the phacofragmenter hand piece without irrigation. While aspirating we approach the nucleus, trap it, lift it so that it reaches the center of the vitreous cavity and emulsify it at this site in 3D mode, which allows the simultaneous control of the vacuum and ultrasound power. The nucleus can be refloated using perfluorocarbon liquid to protect the macula from possible damage.4 Compared to phacoemulsification instruments, fragmentation tips are longer for easy reach of the posterior pole but are less efficient when dealing with hard nuclei, lengthening the removal time and therefore increasing the risk of complications (Fig. 1). We use a fragmentation hand piece for vitreous-luxated nuclei of hardness grade II and III or to perform a pars plana lensectomy with the same degree of hardness. When the crystalline lens is soft, we use the vitrectomy probe. Its 0.9 mm diameter means it can be easily introduced through a 20-gauge sclerotomy and its greater length allows the surgeon to work comfortably in the posterior pole without forcing incisions, and thus avoiding folds forming in the cornea, impairing visualization of the posterior pole.

Figure 1  Fragmentation hand piece by Accurus. Four different fragmentation modes exist: linear, momentary, 3D frag and fixed frag. The new 3D fragmentation mode allows simultaneous control of ultrasound power and vacuum power

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Pars plana torsional phacoemulsification (Ozyl ) is possible for removal of retained lens material during pars plana vitrectomy.The major advantage of the Ozil is that it cuts sideways, which functionally shaves the lens, so the lens fragments are not repulsed as they are in traditional phacoemulsification, which uses a back and forth motion. This facilitates the lens fragments staying at the instrument tip and decreases the tendency for the pieces to be pushed away from the tip as happens with the fragmatome. It also reduces the need to go back towards the retina, re-engage the fragment and begin phacoemulsification again.5 The new high-speed vitrectomy machines are equipped with 23-gauge phacoemulsification probes for microincisional transconjunctival procedures.

REFERENCES 1. Girard LJ, Nieves R, Hawkins RS. Ultrasonic fragmentation for vitrectomy and associated surgical procedures. Trans Sect Ophthalmol Am Acad Ophthalmol Otolaryngol. 1976;81(3 Pt 1):432-50. 2. Meredith TA. Pars plana lensectomy by ultrasonic fragmentation. II. A poor procedure for routine cataract extraction. Surv Ophthalmol. 1982;27(2):96, 101-4. 3. Girard LJ. Pars plana lensectomy for subluxated and dislocated lenses. Ophthalmic Surg. 1981;12(7):491-5. 4. Shapiro MJ, Resnick KI, Kim SH, et al. Management of the dislocated crystalline lens with a perfluorocarbon liquid. Am J Ophthalmol. 1991;112(4):401-5. 5. Garg SJ, Lane RG. Pars plana torsional phacoemulsification for removal of retained lens material during pars plana vitrectomy. Retina. 2011;31(4):804-5.

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5.11  FORCEPS AND SCISSORS INTRODUCTION Scissors are used to cut membrane junctions on the retina especially in detachments due to traction. There are two types of scissors: ƒƒ Horizontal (cutting parallel to the retina) for delamination (Fig. 1) ƒƒ Vertical (cutting perpendicular to the retina) used for segmentation (Fig. 2). Both can be manual or automatic. Automatic scissors avoid movement as the surgeon squeezes on them. Recent developments include curved scissors that can be used both for delamination and segmentation. These manual scissors have two springs, although scissors with one spring are preferable for controlled hand movements.

Figure 1  Horizontal scissors by Dorc for delamination by cutting the attachment zones of proliferative tissue to the retina

Figure 2  Vertical scissors of the Accurus system that allows tissue segmentation by grasping the tissue and then cutting. These scissors are pneumatic and their cutting speed can be controlled with the foot pedal

Chapter 5   Instrumentation

105 We use vertical pneumatic microscissors controlled by the surgeon with the foot pedal. It is possible to vary the cutting mode and number of cuts. These scissors are excellent for segmentation.1,2 For delamination, we prefer curved manual scissors (Figs 3A and B). This maneuver can be performed bimanually: with one hand the tissue is secured using forceps and the other hand can be used for cutting the attachment zones. There are several forceps type and design. Forceps are used to remove preretinal, subretinal and neovascular membranes and the internal limiting membrane. We prefer the positive action membrane forceps, which is the movement we are accustomed to. These forceps have diamond powder coated tips to help grasp the membranes. For preretinal membranes, we use fine tipped, diamond-coated forceps, always with positive action (Fig. 4). For subretinal proliferation strands, we use the same type of forceps as for preretinal membranes with positive action. Once the subretinal strand has been grasped, the forceps are rotated to wrap the membrane around the forceps without it breaking. For subretinal membranes it is best to use curved forceps that can easily be introduced under the retina. For the internal limiting membrane, blunt forceps or forceps with a serrated jaw (Figs 5 and 6) are used to directly grasp the membrane or lift up an edge of the membrane and then dissect it.

A

B

Figures 3A and B  Curved scissors we normally use for delamination. (A) View under the microscope; (B) Side view of the same scissors

Figure 4  Grieshaber positive action diamond-coated forceps

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106

Figure 5  Blunt-tipped, positive-action forceps used for fine epiretinal membranes and internal limiting membrane

A

B

Figures 6A and B  Blunt-tipped forceps with a serrated platform that close perfectly at the tips. (A) View under the microscope, forceps open; (B) Same forceps, closed

Among the new forceps appearing in the market, we should mention the Corcóstegui design. These are direct action forceps, with straight edges designed to remove the internal limiting membrane. They are manufactured in 23-, 25- and 27-gauge measurements and in our experience offer an excellent grasp of the membrane, along with its complete dissection. Currently, these are the forceps of choice (Figs 7A and B). We can also use disposable forceps for the internal limiting membrane (Fig. 8). We can also use a pick to dissect or lift membranes. As a pick, we use a sclerotomy blade, which we fold under the microscope at an angle of 90–110° to lift the membrane or create a border (Figs 9A to C). We should always have available foreign body forceps. These are larger than the forceps used for tissues: 19, 18 or 17 gauge. Diamond powdered models are preferable since they provide a good grasp on the foreign body preventing it from falling onto the retina. Tripod-shaped forceps with three hooks to firmly secure the foreign body is another good option (Figs 10A and B). For a large foreign body, the incision may need to be enlarged. Magnetic forceps are sometimes useful.

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107

A

B

Figures 7A and B  Corcóstegui’s direct action forceps designed to remove the internal limiting membrane

Figure 8  Disposable forceps can also be used to remove the internal limiting membrane

A

B

C

Figures 9A to C  Folded MVR blade used as a pick for lifting membranes

A

B

Figures 10A and B  (A) Diamond-coated foreign body forceps by Synergetics; (B) Tripod-shaped forceps

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108

REFERENCES 1. Charles S, Wang C. Pneumatic intraocular microscissors. Arch Ophthalmol. 1981;99(7):1251. 2. Machemer R, Parel JM, Hickingbotham D, et al. Membrane peeler cutter. Automated vitreous scissors and hooked needle. Arch Ophthalmol. 1981;99(1):152-3.

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109

5.12  VITREOUS SUBSTITUTES: MANIPULATORS OF TISSUES INTRODUCTION Vitreous substitutes are introduced into the vitreous cavity to help maneuver or manipulate tissues during surgery.

HYALURONIC ACID Hyaluronic acid is very viscous and slightly heavier than the infusion fluid. It is hydrosoluble and lacks surface tension thus is ineffective for sealing retinal tears. Hyaluronic acid is used by some surgeons for a procedure known as viscodelamination of membranes:1 the membrane is lifted a little and the viscoelastic is introduced to slightly tense the membrane, which facilitates its dissection or segmentation. Hyaluronate is also used to help refloat the nucleus in the vitreous cavity, when trying to keep a luxated crystalline lens in the central zone avoiding its displacement to the periphery because of the convex meniscus formed by perfluorocarbon. Interest in viscodelamination has been rekindled due to the introduction of trypan blue staining of the viscoelastic. The stained viscoelastic is placed under the membranes making it easy to work while avoiding damage to the retina and specific instruments are currently being developed for this purpose.2 Hyaluronate is mainly used as the viscoelastic in anterior pole surgery. In vitreoretinal surgery, it is used to preserve space in the anterior chamber, improve mydriasis, displace blood and to regularize the endothelium in airfilled eyes in aphakic patients with striate keratopathy. This strategy helps successfully complete the air-fluid exchange maneuver. We personally use hyaluronate in two situations: ƒƒ To regularize the corneal epithelium and avoid desiccation during surgery using a noncontact viewing system. The viscoelastic is placed on the cornea such that a physiological saline bubble is then sufficient to work in most cases without the need for constant irrigation of the cornea, which could induce epithelial edema and subsequent de-epithelialization (Figs 1A and B) ƒƒ After combined cataract/vitrectomy surgery, hyaluronate serves to maintain good mydriasis and also avoids the loss of anterior chamber space during indentation maneuvers.

PERFLUOROCARBON LIQUIDS The specific weight of perfluorocarbon liquids (PFCL) is double that of water so that they can press down on the retina and displace any subretinal fluid.

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110

A

B

Figures 1A and B  (A) Placing viscoelastic on the cornea; (B) The surface is regularized with a drop of saline avoiding corneal drying and offering a good image of the fundus

These liquids are therefore often used in maneuvers performed on the retina in many retinal diseases.3-6 Perfluorocarbon liquids have a high surface tension and therefore tend to form a single bubble such that they cannot pass through retinal tears. When there is retinal traction, however, as the PFCL is injected, the retina lifts up in the shape of a tent and the PFCL bubble eventually penetrates behind the retina since the traction prevents the bubble flattening the retina. To avoid this, we should relieve any traction even if this means undertaking a retinotomy. Because of their low viscosity, PFCL can be easily injected and removed through the cannula. The use of a Chang double cannula is recommended to eliminate liquid from the globe while injecting PFCL, avoiding intraocular pressure peaks and vitreous blocking the infusion cannula (Fig. 2). Perfluorocarbon liquids are optically clear, yet their refractive index is different from that of physiological saline such that they can be easily visualized during surgery (Table 1). The refractive power of the eye is unaffected by the use of PFCL and they can be used when dissecting membranes using conventional or wide-angle lenses. Perfluorocarbons do not absorb laser radiation allowing endophotocoagulation under the PFCL bubble. The refractive index of perfluoro-n-octane is 1.27 and it is easily visible in saline solution. Its interface is therefore easy to see during exchanges and it is the liquid we use in routine practice (Figs 3A to C).

Figure 2  A Chang double cannula is used to introduce perfluorocarbon while allowing the exit of fluid

Chapter 5   Instrumentation

111 TABLE 1 Properties of perfluorocarbon liquids Perfluoroctano

Perfluorodecalin

Perfluoro-hydro phenanthrene

Chemical formula

C8F18

C10F18

C14F24

Molecular weight

438

462

624

Specific gravity

1.76

1.94

2.03

Refractive index

1.27

1.31

1.33

Viscosity

0.69

2.7

7.80

Vapor pressure

105

177

215

Surface tension

17

16

23.9

Tamponade

3.65

4.55

5.0

Trade name

F-octane

DK-line

Vitreon

A

B

C

Figures 3A to C  Perfluoro-n-octane introduced using a Chang cannula; its two channels allow liquid to exit the eye as the perfluorocarbon liquid is introduced avoiding intraocular pressure peaks. (A) Starting the maneuver; (B) Reattaching the retina; (C) Large perfluorocarbon bubble with the retina reattached

Perfluorodecalin has also been used by many surgeons with good results, yet it is more viscous and its interface is less easily observed than perfluoron-octane. Perfluoro hydrophenanthrene is very viscous and thus more difficult to work with during exchanges. Moreover, the aqueous-perfluoro hydrophenanthrene interface is difficult to see and sometimes the physiological saline has to be replaced with air in order to localize it. Visualization depends on the difference between the refractive index of water (1.33) and that of the perfluorocarbon. Thus, the similar refractive index of perfluoro hydrophenanthrene and water means it is impossible to observe the bubble-saline interface.7 Perfluoro hydrophenanthrene is used for tamponade of inferior tears, but in all cases contact time should be short, some 15 days, since there have been descriptions of its dispersion, retinal damage owing to its weight, cataracts in phakic patients and increased intraocular pressure.8

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REFERENCES 1. McLeod D, James CR. Viscodelamination at the vitreoretinal juncture in severe diabetic eye disease. Br J Ophthalmol. 1988;72(6):413-9. 2. Fortun JA, Hubbard GB. New viscodissection instrument for use with micro— incisional vitrectomy in the treatment of diabetic tractional retinal detachments. Arch Ophthalmol. 2011;129(3):352-5. 3. Chang S. Low viscosity liquid fluorochemicals in vitreous surgery. Am J Ophthalmol. 1987;103(1):38-43. 4. Chang S, Ozmert E, Zimmerman NJ. Intraoperative perfluorocarbon liquids in the management of proliferative vitreoretinopathy. Am J Ophthalmol. 1988; 106(6):668-74. 5. Mathis A, Pagot V, Idder A, et al. Use the perfluorodecalin during vitrectomy in diabetics. J Fr Ophthalmol. 1993;16(11):584-90. 6. Comaratta MR, Chang S. Perfluorocarbon liquids in the management of complicated retinal detachments. Curr Opin Ophthalmol. 1991;2(3):291-8. 7. Meffert S, Peyman GA. Intraoperative complications of perfluoroperhydro phenanthrene: subretinal perfluorocarbon, retinal slippage and residual perfluorocarbon. Vitreon Study Group. Can J Ophthalmol. 1999;34(5):272-80. 8. Bottoni F, Bailo G, Arpa P, et al. Management of giant retinal tears using perfluorodecalin as a postoperative short-term vitreoretinal tamponade: a long-term follow-up study. Ophthalmic Surg. 1994;25(6):365-73.

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5.13  VITREOUS SUBSTITUTES: TAMPONADES INTRODUCTION Tamponade agents are introduced in the globe at the end of surgery to seal retinal tears and avoid liquid seeping into the subretinal space. Tamponades also provide time for scarring to occur after retinopexy is performed during the surgery. Gases or air are generally used as temporary tamponades, while silicone oil is used for prolonged tamponade.

INTRAOCULAR GASES Ohm was the first to reattach the retina by air injection in 1911.1 Rosengren subsequently described the concepts of internal tamponade in terms of the site of tearing and an adequate head position.2 However, scleral buckles were soon to replace the use of gas to treat the detached retina and the tamponade method was subsequently revived by a series of studies performed by Norton.3 Following the advent of vitreoretinal surgery, the effectiveness of gas, especially sulfur hexafluoride (SF6), was again recognized. Lincoff 4,5 examined the properties of perfluorocarbon gases, particularly their capacity to expand and persist in the globe. Dominguez6 and later on Hilton described the procedure of pneumatic retinopexy, using gas to seal the tear and then retinopexy in selected cases without the need to indent and on an ambulatory basis. Today, air is routinely used for many types of exchanges in intraocular surgery and several gases are used for tamponade. Air and other gases injected into the vitreous show no toxicity towards ocular tissues. The noxious effects of gases are mainly related to their physical properties such as volume expansion, which produces an increase in intraocular pressure (IOP). However, prolonged contact of a gas with the endothelium or posterior crystalline lens surface can lead to endothelial damage or cataract, respectively. The beneficial effects of a gas bubble for the treatment of a detached retina is the tamponade produced by the functional sealing of a retinal tear and flotation pressure, which presses the retina up against the globe wall. When the patient’s head position is such that the bubble touches an open retinal tear, the tamponade effect prevents any fluid from the vitreous cavity to seep via the tear into the subretinal space. When all retinal tears are sealed by the bubble, the retinal pigment epithelium absorbs any subretinal fluid and the retina is flattened against the back wall of the globe. It is unlikely for a gas bubble to pass through the tear into the subretinal space, but this could occur if the tear is larger than the bubble or if existing membranes prevent the flattening of the retina against the globe wall. Gases used for intraocular surgery are of high molecular weight and

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114 elements from the blood pass into the gas in three different stages: bubble expansion, equilibrium and dissolution. In the expansion stage, nitrogen and other gases enter the bubble and expand it. This usually occurs 6–8 hours after gas injection.7 The equilibrium stage starts at the point of maximal expansion and continues until the partial pressure of nitrogen in the gas bubble and in the blood capillaries reach equilibrium. When this happens, the bubble stops expanding and slowly starts to be reabsorbed. The last stage starts when the nitrogen pressure in the bubble is greater or is in equilibrium with the pressure in the capillaries. This leads to diffusion of elements outside the bubble with the consequent reduction in bubble size (Table 1). The surgeon should be familiar with the properties of the gas and choose the gas according to the condition to be treated (Table 2): ƒƒ Superior tears with retinal detachment (RD) without proliferation can be treated with air ƒƒ Inferior tears with RD can be treated with 20% SF6

TABLE 1 Angle of contact the bubble makes in the vitreous cavity according to the percentage bubble and the volume of gas needed in the phakic eye Contact with the retina

Percentage of gas bubble and volume needed in phakic eyes

120°

25%, 0.50 ml

180°

50%, 1.95 ml

240°

75%, 3.10 ml

360°

100%, 3.91 ml

TABLE 2 Properties of gases used for tamponade Expansion rate

Expansion delay (Days)

Longevity (Days)

Slightly expansive concentration (%)

Nonexpansive concentration (%)

Air

0

0

5–7

0

0

Sulfur hexafluoride (SF6)

2

1

15

20–25

20

Perfluoroethane (C2F6)

4

1.5

30

17–20

16

Perfluoropropane (C3F8)

3.3

3

60

14–17

12

Chapter 5   Instrumentation

115 ƒƒ Complex RD with proliferative vitreoretinopathy or giant tears can be

treated with 10–15% C3F8 ƒƒ Macular holes, if recent, can be treated with C3F8 or SF6. A face-down head position should be maintained until the bubble decreases by 20% to avoid contact with the crystalline lens in an upright position. It should be remembered that a laser-induced chorioretinal scar could appear during the first few days. With cryotherapy, adhesion of the choroid to the retina occurs as early as the 6th or 7th day after surgery. The active proliferation stage can last around 50 days. The use of nitrous oxide in general anesthesia is contraindicated if a gas has been introduced during surgery, since any nitrous oxide inhaled by the patient can pass from the blood to the eye and give rise to a high IOP, eventually occluding the central retinal artery. Conversely, if the patient inhales nitrous oxide after air-gas exchange, the gas will pass to the vitreous cavity, and at the end of the surgery will return to the blood flow, substantially diminishing the effective gas volume. Nitrous oxide is eliminated from the blood in 10–12 minutes, which is the time we would have to wait before using intraocular gas after gas inhalation. Variations in atmospheric pressure affect the total volume of the gas bubble. Thus, if there is an abrupt change in outside pressure, the gas volume tends to expand and this occurs when we travel by air or rapidly climb to a high altitude. At altitudes higher than 1,000–1,500 meters above the height at which the gas bubble was injected, the increase in volume can be considerable and even dangerous. Thus, a patient travelling to a place of high altitude should do so slowly, to allow the gradual expansion of the gas.

SILICONE OIL This oil is lighter than water and tends to float upwards achieving good tamponade of the superior retina. An inferior iridectomy is needed to allow circulation of the aqueous humor such that it does not build up posteriorly and displace the bubble towards the front of the globe. Silicone oil is usually introduced through an injection pump after reattaching the retina and keeping it in position with air. The direct exchange of perfluorocarbon-silicone oil is also possible. The oil is available in 1,000 and 5,000 centistokes. Both show similar behavior in terms of maintaining the retina in position. Silicone oil of 5,000 centistokes can be left in the eye for longer, but the vitreotome used for its removal has to have a liquid extraction pump (Box 1). Silicones are inert hydrophobic compounds of the siloxane polymer family whose viscosity is determined by polymer length. Silicone oil has a refractive index of 1.4035, which is slightly higher than that of vitreous gel at 1.33.8,9 When used it produces hyperopia in the phakic or pseudophakic patients because of the concave surface of the silicone bubble. Conversely, in the aphakic

Step by Step Vitrectomy

116 Box 1: Main properties of silicone oil for its use in vitreoretinal surgery • Transparent, nonvolatile and immiscible in water • Exerts pressure on the superior retina • This tamponade agent is physically weaker than gas (floating power and interfacial tension lower than gas) • Occupies the vitreous cavity in a permanent manner

patient, the convex curvature of the silicone bubble increases dioptic power, reducing hyperopia and tending towards myopia. In these patients, as the head is moved, the silicone bubble changes its curvature, varying its refractive state. Hence, it is difficult to determine refraction in aphakic subjects with silicone oil, especially if the globe is incompletely filled allowing the silicone to move more freely. In 1958, Stone was the first person to describe the use of silicone10 as a vitreous substitute that can remain indefinitely in the globe. Its density of 0.97 g/cm3 is lower than that of water such that it floats over the fluid in the vitreous cavity. The surface tension of silicone oil is far less than that of gas, which along with its reduced floating capacity makes it a much less resistant tamponade agent than gas. Silicone oil is particularly suited for the repair of a superior retinal tear, but proliferations often appear in the inferior retina, such that indentation should be placed inferiorly to contact the ball of silicone, especially if there are tears or inferior membranes.11

Silicone Solvent When silicone oil has been used in a patient with retinal problems, who has undergone prior cataract surgery with the implant of a silicone intraocular lens (IOL) (as the oil interacts with the IOL) blurred, distorted or even double vision is produced. To resolve this problem, research efforts have led to the use of semifluorinated alkanes as a silicone solvent. In Europe, the use of perfluorohexyloctane (F6H8) was approved for this purpose in 1998. Silicone is extracted from the lens using a syringe. Subsequent to this, semifluorinated alkanes have been used to dissolve drops of intraocular silicone oil. This use has proved to be efficient and recommendable. Compared to perfluorocarbons (density 1.8–2.0 g/cm3), F6H8 has a lower density (1.36 g/cm3) and could be less damaging to the retina while preserving some of the benefits of perfluorocarbon liquid such as surface tension (Fig. 1). This has led to suggestions of the use of F6H8 as temporary tamponade in cases of inferior proliferations or tears. Several authors have assessed its use and some have reported significant problems such as redetachments, high IOP, cataract, emulsification, etc.12-16 We employ perfluorohexyloctane as a solvent to remove all the drops of silicone oil and, as such, its use is extremely easy and efficient. In few cases

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117

Figure 1  Silicone solvent can also be used as a tamponade in inferior retinal detachments

we have used it as a tamponade for recurrent inferior detachments, we have always managed to reattach the retina but have noted emulsification in each case and sometimes, intraocular hypertension. We therefore consider F6H8 as a therapeutic tool for use in very selected cases and always with caution. We do not recommend mixing it with silicone oil for inferior and superior tamponade since it forms an opalescent mixture that is difficult to manipulate. Nevertheless, there is currently a compound available that contains 69.5% ultrapure polydimethylsiloxane and 30.5% perfluorohexyloctane (Densiron 68), which is immiscible in water, with a density of 1.06 g/cm3 and viscosity 1400 mPas. This compound has been recommended as a short-term tamponade, but has also been described to induce complications such as glaucoma and cataract.17

Heavy Silicone Oil Oxane HD The low density of silicone oil induces fluid deposition in inferior quadrants and increases the percentage of inferior reproliferations. This has prompted the development of new vitreous substitutes with greater density than water which allows the repair of retinal tears in inferior quadrants (Fig. 2). Heavy silicone oil is a new vitreous substitute with a high specific gravity. It is a mixture of silicone oil of 5,000 centistokes and fluorinated and hydrocarbonated olefin (RMN3). The mixture is homogeneous and stable in the presence of water, air or perfluorocarbon.18 Heavy silicone oil has been used to treat retinal detachments complicated with vitreoretinal proliferation grade C2 or higher, retinal detachment due to

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118

Figure 2  Oxane HD is used in complicated cases for inferior and posterior tamponade

Figure 3  High density silicone for temporary tamponade

eye trauma and giant or inferior retinal tears. The mean period recommended for its placement is 3 months after which time it has to be surgically removed. An 18% rate of increased IOP has been described.19,20 In our experience, heavy silicone oil is a good tamponade for inferior and posterior problems but is not very good for tamponade of the superior zone. The patient should be strictly followed to check for complications so that, if necessary, the oil can be rapidly removed with the help of a fluid extraction pump.

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119

Densiron This product is a stable mixture of silicone solvent (F6H8) and Siluron 5000. Its density of up to 1.06 g/cm3 makes it an efficient tamponade and it is easy to use and shows little tendency for dispersion. Its use should be limited to complex cases; at most it may be left for 3 months before its removal (Fig. 3). For complicated cases, it is currently our product of choice. It should be noted, however, that it is not possible to achieve a total tamponade effect across the whole retinal surface.

REFERENCES 1. Ohm J. Uber die Behandlung der Netzhautablösung durch operative entleerung der subretinalen flüssigkeit und einzpirtzung von luft in den glassköpen. Albrecht Von Graefes Arch Ophthalmol. 1911;79:442-65. 2. Rosengren B. Über die behandlung der netzhautablosung mittelst diatherme und luftinjektion in den glasköper. Arch Ophthalmol. 1938;16:3-42. 3. Norton EW, Aaberg T, Fung W, et al. Giant retinal tears. I Clinical management with intravitreal air. Am J Ophthalmol. 1969;68(6):1011-21. 4. Lincoff H, Mardirossian J, Lincoff A, et al. Intravitreal longevity of three perfluorocarbon gases. Arch Ophthalmol. 1980;98(9):1610-1. 5. Lincoff A, Haft D, Liggett P, et al. Intravitreal expansion of perfluorocarbon bubbles. Arch Ophthalmol. 1980;98(9):1646. 6. Dominguez A. Cirugía precoz y ambulatoria del desprendimiento de retina. Arch Soc Esp Oftal. 1985;48:47-54. 7. Chang S. Intraocular gases. In: Ryan SJ, Wilkinson CP (Eds). Retina, 3rd edition. St Louis: Mosby; 2001. pp. 2147-61. 8. Crisp A, De Juan E, Tiedeman J. Effect of silicone oil viscosity on emulsification. Arch Ophthalmol. 1987;105(4):546-50. 9. Gabel VP, Kampik A, Burkhardt J. Analysis of intraocularly applied silicone oils of various origins. Graefes Arch Clin Exp Ophthalmol. 1987;225(3):160-2. 10. Stone W. Alloplasty in surgery of the eye. N Engl J Med. 1958;258(10):486-90. 11. Vitrectomy with silicone oil or sulfur hexafluoride gas in eyes with severe proliferative vitreoretinopathy: results of a randomized clinical trial. Silicone Study Report 1. Arch Ophthalmol. 1992;110(6):770-9. 12. Kirchhof B, Wong D, Van Meurs J, et al. Use of perfluorohexyloctane as a longterm internal tamponade agent in complicated retinal detachment surgery. Am J Ophthalmol. 2002;133(1):95-101. 13. Zeana D, Becker J, Kuckelkorn R, et al. Perfluorohexyloctane as a long-term vitreous tamponade in the experimental animal. Experimental perfluorohexyloctane substitution. Int Ophthalmol. 1999;23(1):17-24. 14. Roider J, Hoerauf H, Kobuch K, et al. Clinical findings on the use of longterm heavy tamponades (semifluorinated alkanes and their oligomers) in complicated retinal detachment surgery. Graefes Arch Clin Exp Ophthalmol. 2002;240(12):965-71. 15. Stefaniotou MI, Aspiotis MV, Kitsos GD, et al. Our experience with per­ fluorohexyloctane (F6H8) as a temporary endotamponade in vitreoretinal surgery. Eur J Ophthalmol. 2002;12(6):518-22.

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120 16. Gerding H, Kolck A. Perfluorohexyloctane as internal tamponade in patients with complicated retinal detachment. Results after 6 months. Ophthalmologe. 2004;101(3):255-62. 17. Schatz B, El-Shabrawi Y, Haas A, et al. Adverse side effects with perfluorohexyloctane as a long-term tamponade agent in complicated vitreoretinal surgery. Retina. 2004;24(4):567-73. 18. Mathis A, Grosmaire V, Garcia P, et al. Etude expérimentale de la tolérancia intraoculaire d´un nouveaux produit de tamponnement interne en chirurgie vitréorétinienne: résultats préliminaires. In: Societe Francaise d´Ophtalmologie. Paris; 1999. p. 92. 19. Wolf S, Schön V, Meier P, et al. Silicone oil-RMN3 mixture (“heavy silicone oil”) as internal tamponade for complicated retinal detachment. Retina. 2003;23(3):335-42. 20. Avitabile T, Bonfiglio V, Buccoliero D, et al. Heavy versus standard silicone oil in the management of retinal detachment with macular hole in myopic eyes. Retina. 2011;31(3):540-6.

Chapter 6

Basic Vitrectomy José Juan Martínez-Toldos, Cristian Fernández-Martínez

CHECK LIST Before embarking on a vitrectomy, it is the task of the surgical team to make sure that all the equipment are working properly, and all the drugs and instruments we may need are at hand. Making a checklist is recommended including all the items that need to be checked before the patient lies down. This checklist should be drawn up by each surgery team since there could be variations in the instruments, adjuvants or other systems regardless of the surgical procedure scheduled. Table 1 lists the essential points that should be checked before starting a vitreoretinal surgery:

TABLE 1 Points to check before a vitreoretinal surgery Items

Essential points to be checked

Operating table

Comfortable, head parallel to ceiling, eye well-centered

Surgeon’s chair

Positioned such that the surgeon is at the height of the patient’s head

Foot pedals

Easily accessed

Microscope

X-Y drive centered, focus on “0”

Visualization

Lenses available, good condition

Laser filter

Laser in rest position

Infusion line

Purged, bottle at level of patient’s head

Vitreotome

Check aspiration and cutting functions using saline

Illumination Instruments Adjuvants

Check probes Forceps and other instruments, availability, sterile Availability, good condition

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122

POSITIONING THE PATIENT We should dedicate a few minutes to the correct position of our patient: the head, resting on a silicone or gel donut, should be parallel to the ceiling such that the chin is in line with the chest and it must be checked that the eye appears in the microscope’s center of vision. The operating table should be comfortable, otherwise after the 1st hour of surgery the patient will become restless and any movement will hinder the surgery. Some patients even request that surgery be detained. The surgeon usually sits at the 12 o’clock position but may adopt a temporal position in certain situations (scleral problems, certain membranectomies, etc.). It is best to have an oxygen supply close to the patient’s airway in case local or regional anesthesia is needed. We recommend that the surgeon set the position of all nonsterile items (stretcher, patient, surgeon’s chair, armrests, pedals, etc.) before scrubbing in to avoid the risk of infringing conditions of sterility. If during surgery any nonsterile item needs to be repositioned, this would be best accomplished by someone outside the surgery team under the instructions of the surgeon.

VISUALIZATION SYSTEMS There are two main types of visualization systems: (1) contact systems and (2) noncontact systems.

Contact Systems These are lenses that need to be placed in contact with the corneal surface to visualize the eye fundus. Many of these systems require a lens retaining ring fixed to the sclera to give the lens stability and prevent its movement or decentring. The most widely used device (the one we also use) is the Landers metal ring, which is placed close to the limbus and sutured to the sclera at 12–6 o’clock position using 6-0 vicryl sutures. Alternatively it may be obliquely positioned at 3–9 o’clock if the sclera is affected by previous surgery (Fig. 1). Lenses with stabilizing systems that do not require a retaining ring may also be used.

Noncontact Systems These lenses do not need to make direct contact with the globe to allow good visualization of the fundus. They are incorporated in the microscope at the end of an articulated arm so that they can be easily placed or withdrawn during surgery. Although they do not need a retaining ring, the quality of visualization can be affected by corneal desiccation. To avoid this, we recommend abundant rinsing with balanced saline solution (BSS) followed by evenly coating the

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123

Figure 1  The Landers lens retaining ring gives stability to the wide-field lens used in surgery

entire corneal surface with a viscoelastic/methylcellulose. This provides stable corneal transparency without the need to constantly irrigate the corneal surface.

CONJUNCTIVAL INCISIONS The generalized use of microincisional vitrectomy has substantially reduced the need for conjunctival incisions in a large number of cases. However, the conjunctiva will need to be accessed in the following situations: ƒƒ For sclerotomies when 20-gauge caliber instruments are to be used ƒƒ For openings designed to remove a tumor or an intraocular foreign body ƒƒ For implanting scleral indentation devices, whether segmental or circular. If we wish to place a scleral buckle, a 360° conjunctival peritomy is first undertaken. The conjunctiva and Tenon’s capsule are dissected 2.5 mm from the limbus to expose the underlying sclera, leaving a 2.5 mm margin of perilimbal conjunctiva to promote tissue regeneration after surgery. Points of bleeding are coagulated with bipolar diathermy. Following this, the rectus muscles are captured using a hook and a silk 4-0 suture is thread around the insertion point to mobilize the eye, passing the scleral buckle under the muscles. It is helpful, if forceps are fixed to the suture to traction the muscles and help access the globe. If a scleral buckle is not used, we make three transconjunctival incisions: (1) a temporal superior one (3.5 mm from the limbus) to perform the temporal sclerotomy in order to introduce the vitreotome handpiece, (2) a temporal inferior for the infusion cannula (Fig. 2) and (3) one more sclerotomy in the nasal superior zone for endoillumination.

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Figure 2  Conjunctival opening for superior temporal and inferior temporal scleral incisions for the infusion port

SCLEROTOMY Scleral incisions are made with a double cutting edge triangular scalpel, or microvitreal (MVR) blade, whose size varies according to the incision size selected by the surgeon (Box 1). Sclerotomies should be placed close to the horizontal meridians so that access to the inferior and superior periphery is possible.1 Sclerotomies are directly scleral in 20-gauge procedures and transconjunctival with the use of trocars for 23-, 25-, and 27-gauge vitrectomy. The scleral tunnel access technique for suture-free microincisional vitrectomy (23-, 25-, 27-gauge) has been the subject of numerous studies, since on this—in large measure depends the final sealing of the sclera. Most recommendations are based on the individual surgeon’s experience. We conduct an approximation mostly in an oblique direction and then with a gentle turn of the hand we adjust this direction toward one perpendicular to the globe and leave the trocar in place. This achieves an oblique tunnel in the scleral thickness comprised of two Box 1: Sclerotomy equivalents in mm of the different microvitreoretinal gauges 19 gauge = 1 mm 20 gauge = 0.9 mm 21 gauge = 0.8 mm 22 gauge = 0.7 mm 23 gauge = 0.6 mm 25 gauge = 0.5 mm 27 gauge = 0.4 mm 30 gauge = 0.3 mm

Chapter 6    Basic Vitrectomy

125 lips which at the end of surgery will tend to apposite themselves one over the other, thus producing a tight seal without the need for sutures (Figs 3A to D). As mentioned in the first chapter, sclerotomies should be placed on the pars plana as far away as possible from the crystalline lens (3–3.5 mm from the limbus in aphakic or pseudoaphakic eyes and 3.5–4 mm in phakic eyes). Three sclerotomies are usually placed: an initial inferior-temporal to insert the infusion cannula and two superior incisions close to the horizontal globe axis (between 2 o’clock and 3 o’clock, and 9 o’clock and 10 o’clock) to allow for bimanual surgery. Once the infusion line (previously purged) has been introduced, it is important to check that it is correctly positioned in the vitreous chamber before initiating infusion. This can be done by pressing on the tube and illuminating from outside using the optics fiber (Figs 4A and B). The infusion cannula we normally use is 3.5–4 mm with the slant aimed toward the crystalline lens to avoid jabbing the lens if the tube bends. There are also 2.5 mm cannulas, which we use in children and 6 mm cannulas, which we use in cases of anterior proliferations, choroid detachments, anterior trauma, and any time we anticipate difficulty in reaching the vitreous cavity with the cannula. In these cases, we can start surgery placing the cannula in the anterior chamber and it is even possible to conduct a three-port transcorneal vitrectomy.2 At the onset of vitrectomy, it is recommended that the vitreotome be used to eliminate the vitreous that could impede infusion flow through the cannula (Figs 5A and B). Similarly, after marking the nasal and temporal sclerotomies aiming for a separation of 160°, we introduce the MVR blade in the same way toward the center of the eye. We start off with the nasal sclerotomy for endoillumination and finish with the temporal sclerotomy for the vitreotome. Next we introduce

Figures 3A to D  Constructing a scleral tunnel. (A) Direction of the sclerotomy. (B) Placement of the trans-scleral trocar to introduce and withdraw the instruments. (C) Tunnel anatomy after removing the trocar and the actions of positive intraocular pressure. (D) Scleral lips in apposition seal the sclera

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126

A

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Figures 4A and B  (A) Checking the infusion cannula is in the vitreous space; (B) View of the infusion cannula with its slanted tip facing upward

A

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Figures 5A and B  (A) Freeing the infusion cannula from tissue impeding its entry into the vitreous chamber; (B) We can watch the procedure as we push in the cannula and free it from surrounding tissue using the vitreotome, leaving it in the vitreous cavity before starting infusion

the instruments: first the endoillumination probe and then the vitreotome directed toward the eye center. The vitreotome is introduced active to start creating the vitreous tunnel. If during the insertion maneuver we notice vitreous traction, we should remove the instruments and reintroduce the MVR blade (Fig. 6).

Figure 6  Conditions needed to start vitreous surgery: an open infusion line, a switched on light pipe, an active vitreotome and good visualization provided by the wide-field system

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127

PUPIL MANAGEMENT In this section, we will pay special attention to an essential feature of vitreoretinal surgery, pupil mydriasis. Although the new wide-field visualization instruments provide an excellent view of the eye fundus without the need for intense mydriasis, this is still an important aspect of the preoperative preparation of the patient as a good mydriasis allows the surgeon to better visualize the retina as well as provide easier access to the retinal periphery and vitreous base. Generally, an adequate pupil aperture is achieved with a preoperative regimen which starts at least 1 hour before surgery based on anticholinergic eye drops, such as tropicamide 1% and/or cyclopentolate 1%, instilled every 15–20 minutes in the eye to be operated on. Upon arrival of the patient, a member of the surgery team should check the extent of mydriasis and, if necessary, reinforce this with the same eye drops or by adding an adrenergic such as phenylephrine at 10%. Achieving effective pupil mydriasis may be difficult at the surgery time point’s pre and intraoperative. Preoperatively, this could occur in cases of synechiae, atrophic iris or traumatic iris associated with floppy iris syndrome due to prolonged use of alpha adrenergic agonists. In these situations, we can use mechanical methods of pupil dilation. Eckardt was the first to describe the use of iris sutures for temporal dilation during vitreous surgery.3 Currently, the most widely employed method to achieve mechanical mydriasis is the use of iris hooks. Four of these hooks are placed through the limbus, although, if needed, more than four may be used (Figs 7A and B). We place these hooks at 12–6 o’clock and 3–9 o’clock positions after having introduced a cohesive viscoelastic in the anterior chamber. If the eye is phakic, we perform a paracentesis from the perilimbal sclera to the anterior chamber or load a 25 gauge needle with the hook and introduce it at the level of the limbus. As the needle is withdrawn, the hook stays in the anterior chamber and can then be hooked in the pupil (Domínguez method). When the hooks are well positioned, we can achieve wide, stable mydriasis. However, it is possible that the sphincter may be ruptured causing paralytic mydriasis after surgery.

A

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Figures 7A and B  (A) De Juan hooks from Grieshaber used for mechanical dilation of the pupil. These hooks are easy to place and remove; (B) De Juan hook placed 1 mm behind the limbus

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128 Another possible scenario is intraoperative pupil block. Generally this is caused by an abrupt drop in intraocular pressure (IOP) but may also be due to small intraoperative iris traumatism or to an insufficient preoperative mydriasis. If pupil block occurs, an epinephrine solution of 1:10,000 can be injected in the anterior chamber.

PHACOEMULSIFICATION Today, combined cataract-vitrectomy surgery is evermore frequent, given the high prevalence of retinal disease in patients with established cataract. With the exception of the indications for lensectomy already mentioned, the cataract is approached via the anterior. We use the usual technique for extracting a cataract by the temporal route through a 2.2–2.75 mm clear corneal incision. It is important to remember that ocular tone will vary after phacoemulsification so that if we are going to be using a scleral buckle this should be done before starting cataract surgery to avoid the lack of tone being a source of error and hinder its placement. For the same reason, the infusion port should be set up before phacoemulsification and kept closed until the end of the procedure. Below we describe the technique used for phacoemulsification:

Surgical Technique ƒƒ Temporal clear corneal 2.2 mm or 2.75 mm incision ƒƒ Anterior chamber filled with a mixture of chondroitin sulfate and hyaluronic

acid while expelling the aqueous humor

ƒƒ Paracentesis 90° to the incision ƒƒ Capsulorhexis undertaken with a cystotome using both hands: one to fix

ƒƒ ƒƒ

ƒƒ ƒƒ

ƒƒ

ƒƒ

the eye, always looking for the reflection of the fundus and the other hand to handle the cystotome Nucleus hydrodissected and delaminated with BSS Nucleus fractured using two hooks in a bimanual maneuver: one hook is used to grasp the nucleus and the other one to fracture it. This maneuver shortens surgery, helps remove fragments and reduces the ultrasound energy required Emulsification, optimizing fluid flow to decrease the amount of ultrasound. Many grade II–III cataracts can be aspirated directly after manual fracture Surgery should be as rapid and less aggressive as possible to minimize trauma to the cornea. The cortex is aspirated leaving the capsule clean for subsequent vitreous surgery Once the surgery is over, the anterior chamber is filled with a viscoelastic trying to avoid the entry of bubbles. If this occurs the viscoelastic has to be removed A cross stitch is made to avoid leakage from the chamber during vitreous surgery or indentation.

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129 Placement of the intraocular lens (IOL) should be left to the end of surgery, since pseudophakia permits good visualization of the posterior pole and periphery. The only drawback is that the capsule is difficult to identify during vitrectomy and could be accidentally ruptured with the vitreotome. If this happens, the viscoelastic escapes to the vitreous chamber creating waves in the field of view. This situation normalizes quickly. After the vitreous surgery procedure, the IOL will have to be placed in the sulcus with the lens optics retained by the capsulorhexis. During lens implantation, we should try to avoid high pressure in the vitreous chamber by closing the infusion port. If there is insufficient tone to introduce the injector, the lens cartridge is placed at the incision and the infusion port is opened momentarily while we introduce the cartridge and is then quickly closed after this operation.

Special Cases Vitreous Hemorrhage In these cases there is insufficient visibility for efficient phacoemulsification. In some cases, the eye can be moved with forceps to seek out sufficient backlighting to undertake the capsulorhexis. However, if this is not possible, we can use trypan blue to stain the anterior capsule and perform the capsulorhexis, and a light probe can be introduced through one of the sclerotomies to provide us with sufficient light to remove the cortex. Placement of a Chandelier light probe via a fourth port before the start of phacoemulsification will enable all these steps to be carried out. By turning the microscope light off and using backlighting, we can satisfactorily complete the technique.4,5

REMOVING THE VITREOUS HUMOR: BASIC CONCEPTS The instruments are held with the thumb and index finger of both hands to adequately stabilize them for movements in an anteroposterior and lateral direction. Hand movements always need to be in synchrony with movements induced by manipulations of the globe and the microscope’s position and its adequate focusing. First, the light probe (switched on) is inserted perpendicularly to the scleral wall and slowly, with oscillating motions, is pushed toward the center of the eye. The vitrectomy probe is also introduced until we can see both instruments through the microscope. Before any cutting, the infusion tube should be open and the eye should have the appropriate tone otherwise the eye could collapse and the traction generated could produce tears (Fig. 8). The main objective of vitrectomy is to extract the vitreous and the main objective of the surgeon is to do this in the safest way possible. One of the main risks encountered during vitrectomy is the generation of traction on the

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Figure 8  Endoillumination probe and vitreotome in position ready to initiate a core vitrectomy to treat a vitreous hemorrhage

retina, which could later lead to tears or detachments. The principle solution to traction we have is the cutting function, and the greatest generator of traction is the probe’s aspiration function. However, the vitreous cannot be eliminated without its aspiration so we need to be capable of handling our tools with the necessary dexterity. To do this, we should avoid the zones of greatest vitreoretinal adherence by placing the probe in the most central zone of the vitreous and then start to work at high cutting frequencies while approaching the vitreous we want to cut; because if we wait for the vitreous to come to the probe tip, this will generate more pull. As we make circular movements of increasing diameter cutting and aspirating the central vitreous, we will slowly move toward the equator and periphery. As we seek to cut the vitreous, it is essential that the light pipe is well positioned, as perpendicular as possible to the vitreous for its optimal visualization. As we approach the periphery, the vacuum pressure should be reduced at the expense of slowing down the procedure. The position of the posterior hyaloid varies in each patient. In some individuals, it is detached while in others it is completely adhered to the retina. Once the central and peripheral vitrectomy has been completed, we pass the functioning vitreotome probe over the posterior retinal surface; the observation of waves on the surface is a definitive sign of an attached posterior hyaloid. Injected triamcinolone is of great help in identifying the hyaloid since it gets deposited on the hyaloid. Several ways of removing the posterior hyaloid have been described,6,7 but perhaps the simplest is the use of an active aspiration system with a cannula whose distal end consists of a silicone tube to avoid trapping or damaging the retina (Fig. 9). With a linear vacuum of 400 mm Hg we position the probe close to the optic disk. Suction is slowly started. If the silicone tip bends when occluded, this is known as the fish strike sign. Once the hyaloid has been hooked, we look for the wave sign. To do this, we increase the suction power and slowly lift the probe, watching how the hyaloid detaches as the pull produces a wave on the retinal surface. It is not always possible to observe this wave, especially in myopic patients (Fig. 10). Whenever we perform this maneuver, we should revise the retinal periphery perhaps even with the help of indentation, since as we lift the hyaloid, it is possible to provoke tears in the retina which will need to be treated.

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Figure 9  Silicone-tipped cannula used to remove the hyaloid connected to the active aspiration system in an “extrude” mode

Figure 10  Fish strike sign observed while removing the posterior hyaloid: the silicone tip arches as it hooks the hyaloid. After this maneuver, the hyaloid is eliminated up to the periphery using the vitreotome

ASPIRATION SYSTEMS We cannot overstress the importance of good control of suction power in vitrectomy. In summary, aspiration can be conducted in two different ways: in an active manner through the use of pumps incorporated in the vitrectomy machine and in a passive manner, using the pressure difference between the inside and outside of the eye. Both systems have their given uses and should be adequately dominated by the surgeon.

Active Aspiration This is achieved through the vitrectomy probe to extract the central and peripheral vitreous by combining the vacuum power with the cutting rate to obtain greater or lesser suction as described above. Alcon’s Accurus and Constellation systems have a mode for active aspiration with no cutting, denoted as momentary vitrectomy. In this mode, the vitreotome

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132 aspirates until the level indicated to trap, at the vitreotome mouth, solid or high density structures such as blood clots or remnants of crystalline lens, iris or proliferative membranes. Other vitrectomy platforms like Stellaris PC could also offer this kind of parameters to the surgeon. Once engaged, we can introduce the cutting function for their fragmentation and aspiration (Fig. 11). We also have available active aspiration systems that are independent of the vitrectomy probe, such as the silicone tip (extrusion), which allows us to approach the retina in a safer way and even gently touch its surface without damaging it. This device is especially useful when inducing detachment of the posterior vitreous during surgery or to aspirate blood or subretinal fluid and for fluid/gas exchange. In cases of uveitis or intraocular infections, samples of vitreous humor may need to be obtained for diagnostic purposes. For this we usually use the active aspiration pump, connecting the probe to a final collector from which we can then obtain the sample (Fig. 12).

Passive Aspiration This is achieved through a cannula connected to a flute-like handle with an inner conduct and side opening. With this side opening closed (by the surgeon’s finger) the pressure gradient toward the exterior of the eye is maximal and this promotes the exit of liquid or blood, provided its density is sufficiently low to permit good flow toward the exterior. The aspiration speed can be increased or lowered as the IOP changes (Figs 13A and B). Currently, these passive aspiration systems include a reflux mechanism via the compression of a soft tube in the handle. These are known as backflush systems.

PEELING MEMBRANES IN VITRECTOMY One of the retinal disorders the posterior pole surgeon is most often faced with is the appearance of macular epiretinal membranes. In their most advanced form, these membranes produce radial folds in the macular area causing a loss

Figure 11  Active aspiration generated by the vitreotome pump. Note the vitrectomy probe lifting a blood clot, which can be completely removed by activating the vitreotome’s cutting function

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133

Figure 12  Sample collection by active aspiration. Using a syringe connected to the vitreotome’s aspiration line, the required volume of vitreous is obtained and the aspiration line then reconnected

A

B

Figures 13A and B  Passive aspiration is produced by the difference in intra-and extraocular pressure. (A) The intensity of aspiration will depend on this difference in pressure—the greater the intraocular pressure, the greater the aspiration power; (B) Aspiration cannula capable of manual backflush

of visual acuity and metamorphopsias. These membranes can be removed by their dissection using specially designed forceps following their prior staining. For this purpose, we prefer a dye such as trypan blue under physiological saline and using a magnifying contact lens to visualize the macula in detail, we directly dissect with the forceps searching out the most intensely stained zone of most prominent folding, from which we create an initial flap of tissue to initiate the peeling process. The maneuver should be conducted with utmost care since the risk of iatrogenic trauma to the macula is high. The light probe should be correctly positioned to avoid reflections from the forceps handle, avoid phototoxicity and also achieve adequate illumination of the zone. We recommend keeping the endolight at an equatorial point of the globe and avoiding its movement during peeling. Once the first flap has been created, we continue tractioning from the margin furthest away from the fovea in a circular motion with respect to the surgeon and tangential to each point of the retina. The idea is to obtain an ever-larger flap as the peeling process ensues,

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134 but unfortunately this is not always possible and the initial flap tears. In this case, we start the procedure again not necessarily at the same point although it is true that the contrast between the already peeled and still adhered stained tissue really helps construct a new flap. We should always try to leave for the end the peeling of the perifoveal area, since excessive traction on adhered tissue at the fovea could lead to the formation of a hole over the fovea. It is therefore recommended that peeling is achieved from the most external and furthest away part of the flap with respect to the fovea. Once peeling has been done over 360° around the fovea, we can then proceed with the definitive separation of the membranes by means of a gentle anteroposterior movement (Figs 14A to C). For scarcely stained and discrete membranes, an option is to create the initial flap using a more or less sharp dissector known as a pick, which facilitates the initial dissection of the membrane. If we do not have such an instrument, we can use a 20/23-gauge needle and bend over its tip with a needle holder some 90–100° under the microscope. Sometimes the membranes we are faced with are the consequences of other serious diseases of the eye such as detached retina or proliferative diabetic retinopathy (PDR). In these cases, epiretinal membranes have greater traction capacity and they use the posterior hyaloid as a support to extend from one point to another of the retina, creating bridges that cause traction and can detach the retina. The strong anchoring of such membranes and the poor state of the retina makes their peeling especially risky. It is easy to cause iatrogenic tears and consequently we should undertake a bimanual procedure of segmentation and delamination to remove them. In some cases, we recommend the use of liquid perfluorocarbon to stabilize the retina and aid these maneuvers (Figs 15A and B).

Segmenting Membranes Parallel arm scissors (manually or pneumatically controlled) are used to cut the bridges of proliferation tissue and fragment these membranes into separate islets, and thus minimize traction on adhesion zones. The lower blade of the scissors can be used as a pick to identify the adequate plane and also to lift the

A

B

C

Figures 14A to C  (A) Macular pucker generating traction on the macula; (B) Starting the dissecting procedure on the clear separation border; (C) Tangential movements used to remove the membrane

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135

A

B

Figures 15A and B  (A) Dissecting the membrane under perfluorocarbon. Note the traction folds; (B) Freeing the macula, observing the separation and freeing of the membrane

tissue for its dissection prior to cutting.8-10 It is common that the edges of the epiretinal tissue widely separate after they are cut indicating that the membrane was generating considerable traction (Figs 16A and B). Membranes can also be segmented using curved scissors, by passing one of the blades under the membrane, producing slight traction upward and then sectioning. The design of current vitreotomes with the mouth so close to the tip permits a safe approach to the retina, and in many cases, the rapid and safe segmentation of the membranes.

Delaminating Membranes This consists of dissection with horizontal scissors, cutting the fixation points between the proliferation and the retina without first dividing epicenters of traction. This technique allows a more complete elimination of proliferative tissue (Figs 17A and B). Curved or right angled scissors may be introduced in the junction epicenters, slightly raising the scissors before cutting to avoid damage to the retina and its vessels. Delamination is generally performed bimanually. Forceps are used to lift the tissue, and with the other hand, the scissors used to

A

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Figures 16A and B  (A and B) Segmenting membranes. With the help of vertical scissors, the junction bridges that are raised slightly above the retinal tissue are cut

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136

A

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Figures 17A and B  (A and B) Bimanual membrane delamination procedure: lifting the proliferative tissue with one hand, and using the other hand to cut the junctions with horizontal scissors

cut the junction sites are held. A light source independent of the instruments is needed, such as a light fitted to the infusion cannula, or light can be provided by one of the instruments. Instruments with a light source have the drawback that they create shadows. We use the Chandelier light through the fourth port. The membrane manipulator has also been used for this procedure, which has endoillumination, aspiration to retain the membrane and diathermy in case of bleeding. The noncontact visualization system optical fiber free intravitreal surgery system provides endo-ocular illumination through the microscope such that bimanual delamination can be performed without lit instruments. In most cases of PDR, segmentation and delamination are combined.11-13

Staining Membranes The good visualization of epiretinal membranes and their discrimination from the adjacent or underlying retina is a decisive factor for their adequate removal. To aid this tissue discrimination, several dyes exist which we have described in detail below:

Indocyanine Green It is widely used in the photography and textile industries; cyanines share the features that they are organic dyes of great staining capacity for all types of tissue. Indocyanine green (ICG), approved in the late 1950s by the Food and Drug Administration (FDA) for its medical diagnostic use, is an anionic dye of molecular weight 775 Da used in vitrectomy to stain the internal limiting membrane (ILM) despite not having been explicitly indicated for surgical use14,15 (Figs 18A to C). The mechanism whereby ICG stains the ILM is unclear, but most authors propose that it has something to do with collagen IV, fibronectin and the laminin present in the extracellular matrix comprising the ILM. One of the arguments in favor of its use as a stain is that it greatly facilitates membrane peeling. This was confirmed in an experimental model in the pig, in which ICG staining and subsequent exposure to light increased the

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137

A

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C

Figures 18A to C  (A) Epiretinal membrane of difficult visualization; (B) Staining with indocyanine green perfectly outlines the edges of the membrane facilitating its removal; (C) Rapidly removing the membrane with forceps

stiffness of the ILM.16 Thus, numerous authors have defended and continue to advocate the use of ICG as a safe, nonexpensive dye for peeling.17,18 Various preparations exist in the market: 5, 25 or 50 mg vials such as Indocianina Verde (Ophthalmos), ICG-Pulsion (Pulsion Medical Systems), among others. The powder is reconstituted first with distilled water and then with physiological saline to obtain a solution containing 0.05–0.5% of ICG. Notwithstanding, the use of ICG has been questioned as a consequence of studies indicating toxic changes produced in the pigment epithelium after 30 seconds of contact with ICG. Visual field defects and optic nerve atrophy have also been described with serious consequences on the patient’s visual prognosis.19-24 Currently, this stain is still used by many posterior pole surgeons. In effect, we used it over a few years diluted in glucose at concentrations of 0.05%25,26 but currently we avoid its use. As an alternative, some authors have assessed the use of the dye infracyanine green. Results so far indicate that this stain is somewhat less toxic for ganglion and pigment epithelium cells.27

Trypan Blue This is a synthetic azo dye containing nitrogen in its formula, of molecular weight 960 Da and stains the tissues intense blue. Trypan blue is routinely used to examine the endothelial layer of the donor button before a cornea transplant and has been used in cataract surgery to stain the anterior capsule of the crystalline lens.28 In vitrectomy it is used due to its special affinity for epiretinal membranes and membranes in proliferative vitreoretinopathy (PVR) because of their high contents in glial cells. Despite not being recommended to stain the ILM, in a comparative study with ICG used to peel the ILM in cases of macular hole, it was shown that the percentage of anatomic closure achieved was similar but that the visual outcome was significantly better in the eyes stained with trypan blue.29 Two commercial preparations exist: (1) Membrane Blue [Dutch Ophthalmic Research Center (DORC) International] at a 0.15% concentration and (2) Vision Blue (DORC International) at a concentration of 0.06%. For vitreous surgery, we use the higher concentration preparation

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138 since, once injected in the vitreous chamber, the dye becomes diluted with the irrigation saline. In contrast, for cataract surgery, a low concentration is sufficient to stain the anterior capsule. The product is supplied in a vial in physiological saline with an osmolarity of 257–314 mOsm/kg and pH 7.3–7.6. Its combination with glucosated saline at 5% or 10% increases its density and improves its penetration when the vitreous chamber is filled with infusion saline. However, the osmolarity of this combination is greater such that it may be toxic if used at higher concentrations. Most studies examining the possible retinal toxicity of trypan blue have concluded that there is no evidence for such toxicity, although one report exists of a case of possible pigmentary epithelium toxicity in which the dye migrated to the subretinal space.30 We use trypan blue to stain epiretinal membranes and in some cases to stain the ILM. We found, it stains epiretinal membranes and PVR membranes facilitating their removal (Figs 19A and B).

Brilliant Blue It is an anionic dye with a molecular weight of 854 Da. Also known as acid blue or Coomassie blue, it has been used in the textile, paint and food industries. Since its approval in 2007 for marketing in Europe, its use has been described to stain the ILM as an alternative to ICG with no descriptions of any toxic effect on the retina.31 Marketed as Brilliant Peel (Fluoron, Geuder, Germany) as an iso-osmolar solution of concentration 0.25 mg/ml, it is the stain of choice for many surgeons including the authors. It is a useful tool for visualizing the ILM with high biocompatibility. It is recommended that the eye should be filled with air and then the air and dye removed after use. However, if we dilute brilliant blue in heavy water or glucose solution at 5%, it will be heavier than water and will not need to be exchanged by air prior to its introduction.32

Dye Combinations A combination of trypan blue and brilliant blue (trypan blue 0.15%, brilliant blue G 0.025%) in an aqueous solution, heavier than saline (4% PEG), has recently appeared in the market and this product can be used to stain epiretinal

A

B

Figures 19A and B  (A) Epiretinal membrane; (B) Trypan blue staining

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139 membranes and the ILM. We find it extremely efficient and easy to deposit on the retinal surface en bloc without dispersion. It stains the tissues well and is easy to remove. This combination is a good option especially for surgeons still at an early stage in the learning curve.

Refrigerated Dyes A way of improving contact between the dye and the retina is to store the dyes refrigerated at 4ºC and using them directly from the fridge. Because of their density, cold liquids sink to the bottom when injected, facilitating contact between the dye and epiretinal tissue. Before injection, we close the infusion line to avoid turbulence and slowly introduce the dye. In addition, the hypothermal effect, albeit limited, protects the retina from the possible toxicity of the dye.33,34

Triamcinolone Acetonide It is a synthetic powerful corticosteroid, which is insoluble in water and has a molecular weight of 434 Da. Triamcinolone acetonide was used for the first time by Kimura et al35,36 to peel the ILM, who argued that the deposition of its crystals on the ILM helped them identify and peel the membrane. No adverse effects were recorded in the postoperative course. Currently, it is mostly used to improve the visualization of the posterior hyaloid membrane during vitrectomy, especially in cases in which the joining or incomplete separation of the posterior hyaloid can be a source of traction (e.g. in macular hole, vitreomacular traction syndrome, proliferative and fibrovascular vitreoretinopathy, diabetic retinopathy). Several preparations of triamcinolone acetonide exist such as Triesence (Alcon Labs, Fort Worth, TX, 40 mg/ml), Kenalog (Bristol-MyersSquibb, Peapack, NJ, 40 mg/ml), Trivaris (Allergan, Irvine, CA, 80 mg/ml) or Trigon Depot (Squibbs, 40 mg/ml). Several adverse effects have been related to the use of intravitreal triamcinolone especially when used to treat diabetic macular edema, such as glaucoma, cataract and aseptic endophthalmitis. Studies also exist that have shown that its intravitreal injection is not toxic for retinal cells.37 However, the alcoholic component of the solvent has indeed been described as toxic. Accordingly, several methods have been devised to avoid introducing the solvent in the vitreous including decanting, leaving the ampoule for 24 hours in a vertical position and centrifuging for 3 minutes at 3,000 rpm. Once the solid has been separated from the liquid, the latter is replaced with BSS. Thus, if we dilute the solid in 1 ml of BSS, by injecting 0.1 ml we will be introducing 4 mg of triamcinolone; if we dilute it in 0.5 ml of BSS, 0.1 ml will contain 8 mg. We undertake double washing of the solvent using a three-way stopcock and a 5 µm Millipore filter (triamcinolone molecules will not pass through the filter) taking the following steps:

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140 ƒƒ The filter is positioned ƒƒ The triamcinolone is filtered by pushing the solution through the filter to

eliminate the solvent and retain the solid in the filter

ƒƒ The solid is reconstituted in 2 ml BSS ƒƒ Washing is repeated ƒƒ The liquid is replaced with 1 ml BSS, so that 0.1 ml will give us 4 mg of

triamcinolone. After double washing the triamcinolone, we inject several drops through a sclerotomy and observe that the vitreous becomes impregnated with the corticosteroid facilitating the dissection of the posterior hyaloid. If we wish to remove the ILM, we introduce a little more triamcinolone watching how it impregnates the retinal surface. We should take care not to introduce too much triamcinolone, since an excess of the corticosteroid will make the thickness and plane of the membrane less obvious during peeling (Figs 20A and B). A useful strategy to avoid flooding the field with particles is to pump the triamcinolone through a silicone cannula connected to a silicone lengthener. As the silicone is pressured, the particles are slowly scattered on the tissue surfaces sufficiently to trace the membrane.

PERFLUOROCARBON LIQUIDS Curiously, the use of perfluorocarbon liquids (PFCL) was investigated in medicine as a substitute for human blood due to their high capacity to transport oxygen and good biocompatibility. In ophthalmology, their use as vitreous substitutes was first assessed in experimental animals in which inferior detachment of the retina was induced. Chang et al38 were the first to use PFCL on the human retina in retinal detachment surgery. Perfluorocarbon liquids are colorless, odorless, immiscible in water and have a high density and low viscosity. These properties make them ideal to help the surgeon handle and stabilize the detached retina, as they induce the exit of subretinal fluid through peripheral tears. Their low surface tension makes PFCL arrange

A

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Figures 20A and B  (A and B) Removing the posterior hyaloid with forceps and the vitrectomy probe. Note the membrane is impregnated with particles

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141 themselves as a single large bubble, thus reducing the risk of migration to the subretinal space. Moreover, their low viscosity makes their aspiration very simple facilitating fluid-, oil- or air-exchange. Several perfluorocarbons have been assessed for their use in vitrectomy. Thus, perfluoro-n-octane has been approved by the FDA for intraocular use owing to its high stability and purity compared to other compounds. The most common indications for the use of PFCL in vitrectomy are the treatment of complex detachments, PVR and giant tears. Further indications are detailed in Box 2. The use of a PFCL requires a prior three-port pars plana core and peripheral vitrectomy. It should first be checked whether the posterior hyaloid is detached and if not, we should lift it with a silicone-tipped vitrectomy probe using active aspiration. A wide-field-viewing system has to be used for constant control of the surgical maneuvers.

Uses of Perfluorocarbon Liquids Giant Retinal Tear Surgery for a giant retinal tear has been substantially simplified and nowadays the retina is unrolled and reattached with the patient in a decubitus supine position in a single maneuver. The successful reattachment rate can be up to 90%. In addition, membranes can be removed, the edge of the tear can be treated with endolaser, and surgery can be completed with exchange for air and subsequently for gas or silicone oil. Once the retina is reattached, we can also perform direct perfluorocarbon-silicone oil exchange to avoid the retina becoming subsequently displaced.

Vitreoretinal Proliferation In cases of vitreoretinal proliferation the use of PFCL has improved anatomic and visual outcomes with a success rate between 84% and 96%. The duration of surgery is shortened and as the retina is stabilized, membranes can be easily dissected. As the PFCL is injected, the retina contracted by the membranes opens up facilitating their exposure and visualization. Initially a small amount Box 2: Indications for the use of perfluorocarbon liquids • • • • • • • • •

Retinal detachment with giant tear Retinal detachment with vitreoretinal proliferation Retinal detachment in proliferative diabetic retinopathy Refloating a luxated crystalline lens Refloating a luxated intraocular lens Membrane dissection Bleeding control during vitrectomy Any complex retinal detachment Choroid hemorrhage

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142 is introduced but as we start to remove the membranes and the retina starts to reattach, the volume of PFCL is increased. When the level of the bubble reaches the height of the scleral band, this also helps identify anterior proliferative membranes. Once we have completed the dissection of membranes if the retina is still rigid and will not reattach due to residual tractions, and if these cannot be eliminated, the level of the bubble is lowered and a relief retinotomy is performed until we observe the retina has adequately reattached. At this point in time, we go beyond the level of the retinotomy and seal the retina using the laser. The procedure is then completed by exchanging the PFCL, first for air and then for gas or silicone oil.

Luxated Natural or Intraocular Lenses In cases of a luxated lens, the use of perfluorocarbon is mandatory. If the retina is detached, this will allow for its reattachment and refloating the lens to the anterior chamber to adequately handle it. If the crystalline lens is luxated, PFCL protects the macula from possible damage during its fragmentation in the vitreous chamber. If very hard, the natural lens can also be refloated to the anterior chamber for its anterior removal.

Further Uses Perfluorocarbon liquids can also be used in proliferative retinopathy with rhegmatogenous retinal detachment, bleeding control during vitrectomy, evacuating choroid hemorrhagic detachments or the management of traumatic injuries.

Intraoperative Management of Perfluorocarbon Liquids Injection of PFCL under Physiological Saline To inject the PFCL, we prefer to use a silicone tipped cannula connected to the PFCL syringe. It is best to first lower the IOP by adjusting the infusion rate to avoid IOP peaks with the risk of occluding the central retinal artery and also reducing the risk that infusion fluid turbulence prevents the cohesion of the PFCL into a single large bubble. When working through 20 gauges we usually use the Chang cannula to extract the intraocular fluid as we slowly introduce the PFCL (Fig. 21). As mentioned earlier, the high density of PFCL determines that it attaches the detached retina while displacing the subretinal fluid toward tear zones achieving its drainage. It is important to be aware of the possibility that the perfluorocarbon bubble surpasses the tear zone without all the subretinal liquid having emerged, leaving an anterior ridge of fluid that cannot leave because the tear is tamponaded by the PFCL (Figs 22A and B). If we do not avoid this raised ridge as we replace the subretinal fluid with air it will again move toward the posterior pole. To avoid this situation, we

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Figure 21  Chang cannula with a double lumen allowing the simultaneous injection of perfluorocarbon and the exit of physiological saline

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B

Figures 22A and B  (A) Injecting a perfluorocarbon liquid in a case of retinal detachment.The perfluorocarbon liquid bubble weighs more than physiological saline and displaces the subretinal fluid, which in turn, emerges from the retinal tear and reattaches the retina. As we introduce the perfluorocarbon liquid through a Chang cannula, the saline emerges from the globe such that the exchange maneuver does not provoke an increase in intraocular pressure; (B) Retinal detachment anterior ridge produced as the perfluorocarbon liquid displaces the subretinal fluid upward. If this occurs, the fluid can be subsequently displaced by perfluorocarbon liquid-air exchange

can position the perfluorocarbon bubble close to the tear zone and exchange saline for air, which in this case will displace the fluid anteriorly toward the tear as an upward-downward force, draining and flattening the more anterior retina (Figs 23A and B). Once the retina is reattached, we can proceed with endophotocoagulation, IOL implantation, cryotherapy, scleral buckle placement or buckle readjustment.

Perfluorocarbon Liquids Removal and Air Introduction This is a crucial step during surgery for a detached retina. Before injecting the air, it is important to achieve good subretinal fluid drainage avoiding that the PFCL bubble surpasses the retinal tears. The next step has a dual function: first it strives to remove the saline on top of the PFCL to avoid it repenetrating the tears and second it seeks to drain out any possible subretinal fluid that exists in the more anterior retina. Before initiating the

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Figures 23A and B  (A) Using perfluorocarbon liquid, a retina with donuts of subretinal fluid is reattached as the fluid is displaced anteriorly; (B) This situation can be avoided by performing a double exchange with perfluorocarbon liquid up to the level of the tear and air in the anterior zone which will displace the subretinal fluid forcing its exit through the tear and completely reattaching the retina

exchange procedure, an aspiration probe should be placed at the tear opening (preferably with a silicone tip so as not to jab the retina) to avoid saline entering the subretinal space during the exchange maneuver. Aspiration is started as close to the tear as possible simultaneous to the introduction of air. As the air rises, it will move toward the most anterior zone of the vitreous chamber. This will greatly impair our visualization due to the presence of three substances of varying refractive index (posterior to anterior, PFCLsaline-air) (Fig. 24). We should keep calm and not move the aspiration cannula. As we continue to inject air and aspirate saline, the refractive interface will be gradually lost and we will start to see even more clearly. Gradually, the new PFCL-air interface will be appreciable. We should not be in a hurry to remove the aspiration tube from the mouth of the tear, since small amounts of fluid may remain, pushed by the air from the anterior subretinal space (Figs 25 A and B). Once the anterior retina has been reattached and the saline has been completely eliminated, the aspiration cannula can be placed beneath the PFCL pointing toward the optic disk for its removal, leaving the vitreous cavity filled with air. Despite having carefully followed each step, it is still possible that a small amount of saline escapes through the tear during the exchange process and is subsequently displaced as the air bubble retreats. If the amount of saline is small, by the next day it will have been reabsorbed by the pigmentary epithelium. However, if a large volume of saline seeps behind the tear, the retina will be redetached and the exchange maneuver will have to be repeated, filling the vitreous cavity again with perfluorocarbon.

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Figure 24  Removing perfluorocarbon (blue arrow) and introducing air (green arrow). As the perfluorocarbon is extracted, air is introduced by the infusion pump

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B

Figures 25A and B  (A) Extrusion system positioned at the level of the tear to aspirate the meniscus between the air and perfluorocarbon liquid to avoid it seeping through the tear; (B) Diagram showing this maneuver at the stage when the bubble of air surpasses the tear. The aspiration probe is positioned in the center of the eye on the perfluorocarbon liquid bubble until its complete removal

Perfluorocarbon Liquids Removal without Air Introduction In situations in which the retina is attached, such as in cases of a luxated natural or artificial lens, the vitreous cavity contains saline in the upper zone while the perfluorocarbon occupies the lower area. The aspiration cannula should be positioned over the optic disk and it should be made sure that this is the eye’s lowest point. Then once we have removed the perfluorocarbon, we should allow a few drops of saline to fall on the retinal surface, to wash away any remnants adhered to the retina and then reaspirate the retinal surface.

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Direct Exchange for Silicone Oil The direct exchange of perfluorocarbon for silicone oil can be performed in cases of giant retinal tear with a tendency for displacement of the retina when we exchange for air. In this case, the silicone oil is introduced via the infusion cannula helped by the fluid injection pump. As it is injected, the perfluorocarbon is aspirated with an extrusion cannula until the cavity is completely filled with silicone oil.

Potential Problems during the Use of Perfluorocarbon Although PFCLs are stable and safe compounds, their use is not exempted of certain possible complications. First, a PFCL cannot be left for long in the vitreous cavity since it has a toxic effect on the retina and may also break up into small bubbles that affect optical transparency. However, cases have been described in which a few drops of PFCL remained in the vitreous cavity with no adverse effects noted. Another possible complication in aphakic patients is the alteration of the corneal endothelium as it contacts the PFCL. This may be avoided by the placement of a dispersive viscoelastic over the bubble to protect the corneal endothelium. In patients with a crystalline lens, interaction of the lens with air could result in a small layer of saline becoming trapped between the air and the crystalline lens, hindering visualization during the extraction maneuver. To improve vision, a biconcave contact lens can be added to the wide-field noncontact viewing system. With these measures, visualization can be improved to complete the exchange process in complex cases.

FLUID-AIR EXCHANGE The exchange of fluid for air has the objective of filling the eye cavity with air for purposes such as the adequate tamponade of a sutureless sclerotomy, avoiding ocular hypotony in the postoperative course or for the subsequent injection of a gas or silicone oil. The maneuver is performed with an active or passive aspiration cannula at the upper level of the eye. Air is introduced through the infusion port with the help of the infusion pump 39,40 of the vitreotome set at a pressure of 25–35 mm Hg. We then watch the upper portion of the vitreous chamber filling with air, position the aspiration cannula at the liquid-air interface and start aspirating at a vacuum between 100–150 mm Hg until we reach the area above the disk where we will see that, as we aspirate all the liquid, a different intense reflection or shine appears on the retina (Figs 26A to D). After a complete exchange, fluid will again accumulate at the posterior pole and on the retina and optic disk. This is due to the gradual drainage of the peripheral vitreous and the constant production of aqueous humor. After waiting a few minutes, we can aspirate this residual liquid.

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A

B

C

D

Figures 26A to D  (A) Perfluorocarbon-air exchange. Using the extrusion system, we aspirate the perfluorocarbon at the same time as we introduce the air; (B) Appearance of the interface as we touch the bubble surface; (C) Aspiration is continued until beyond the level of the optic disk; (D) Reflection of the air on the retina. Aspirating remaining fluid

Air offers certain benefits when managing an intraocular hemorrhage since it displaces blood toward the posterior retina and facilitates its visualization as it avoids its dilution with the saline such that it can then be more easily aspirated.41 If we are dealing with a detached retina with a tear that is so posterior that PFCL would be ineffective at achieving drainage of the subretinal fluid, we can use air simultaneously to aspirate fluid from the mouth of the tear with a silicone-tipped cannula. Air remains in the vitreous chamber for 5–7 days and is therefore not adequate for good tamponade of tears until chorioretinal adhesion occurs. However, air can be useful for localized primary retinal detachments without vitreoretinal proliferations, especially superior detachments, and is also useful for treating small tears observed while revising the periphery.

USE OF GAS IN VITRECTOMY Two types of gases exist: (1) nonexpanding gas and (2) expanding gas.

Nonexpanding Gas With a nonexpanding gas, the size of the bubble does not increase after its injection. The most widely used gas of this type is atmospheric air. Xenon is another example although it is currently in disuse.

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Expanding Gas When the gas used is an expanding gas, the size of the bubble increases during the hours after its injection due to the interchange and/or incorporation of other gases dissolved in blood. The most widely used expanding gases are sulfur hexafluoride (SF6) and perfluoropropane (C3F8). Both are odorless and colorless, inflammable and nontoxic. Sulfur hexafluoride, is five times heavier than air while C3F8 is six times heavier. All gases show inert intraocular behavior, avoiding the accumulation of proinflammatory factors, growth factors, etc. and their deposition on the retina thus prevents the development of proliferative membranes. The force exerted by the gas on the retina flattens it and seals tears, avoiding the passage of saline and its consequent redetachment. The floatability of the gas contributes to this action since its specific weight is less than that of water. This property can be used to promote contact between the gas and retinal tear, solely by modifying the position of the patient’s head.

Clinical Indications of Gases Gases are used to achieve adequate tamponade of filtering tears and/or holes over sufficient time for new chorioretinal adhesion bridges to form (promoted by laser impacts) around these tears. This determines that the choice of gas is made according to the condition being treated and the tamponade time deemed necessary. Our general indications are as follows: ƒƒ Primary superior tears with retinal detachment (RD) without proliferation can be treated with air or SF6 20% ƒƒ Inferior tears with RD can be treated with SF6 20% ƒƒ Complex RD with PVR A, B, C1–2 (Retina Society) can be treated with SF6 20% ƒƒ Complex RD with PVR C3, D (Retina Society) or giant tears can be treated with C3F8 10–15% ƒƒ For macular hole it is usually sufficient to use SF6. For recent or small holes, air could be sufficient.

Air-Gas Exchange This is done at the end of surgery when we are about to close the last sclerotomy, which is left presutured. To do this, we use a 60 ml syringe and for a 20% mixture we add 12 ml of pure gas and make up the rest with air to give a nonexpansive mixture. It is important to know that gas aspiration should be conducted through two 0.22 μm Millipore filters: one connected to the pump and the other connected to the syringe. This avoids the introduction of contaminants in the mixture and ensures that the atmospheric air is sterilized as it passes through the Millipore filter. The mixture should be injected as

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149 quickly as possible to avoid the gas diffusing through the plastic comprising the syringe. Using a three-way stopcock, the injection is introduced into the infusion line. The gas is slowly injected in the eye and the air spontaneously escapes through one of the sclerotomies. If the sclerotomy becomes occluded with vitreous remains, a cannula or 25-gauge syringe can be inserted through it to facilitate the exchange. Once 30 ml of the gas mixture has been injected (about 8 times the volume of the vitreous chamber), we know that all the air has been replaced with the air/gas mixture. We should keep a small amount of mixture in the syringe to replace any gas lost when retrieving the infusion line, leaving the globe with an IOP of approximately 20 mm Hg.

Postoperative Management of Patients Receiving Intraocular Gas The safest position for the patient while the gas remains in the eye is the decubitus prone position. This favors contact of the gas with the retina while distancing it from the crystalline lens in phakic eyes, IOL in pseudophakic eyes or the corneal endothelium in aphakic eyes. It also avoids pupil block. This position should be maintained until only a small amount of gas remains in the ocular globe. During the first 12 hours of the postoperative course, at least two doses of oral acetazolamide should be given as prophylaxis. If pupil block occurs, intraocular gas may be removed at the slit lamp by pars plana insertion of a 30-gauge needle connected to a 2 ml syringe and aspiration of approximately 0.7 ml of gas.

SILICONE OIL IN VITRECTOMY Injection of Silicone Oil This is generally done when the retina has been reattached and after fluid/air exchange when the globe is full of air. The silicone is injected with the help of the infusion pump for viscous liquids up to the level of the iris, trying to leave the eye with a normal pressure of some 20 mm Hg. If the eye is left hypertensive, the bubble will be displaced to the anterior chamber as the sclera recovers its shape after being distended by the hypertension, pushing the bubble forward. A PFCL can also be directly exchanged for silicone oil by connecting the siliconecontaining syringe to the infusion line and removing the perfluorocarbon at the same time with another instrument, as the eye is filled with silicone. Current vitreotomes have a system that simultaneously achieves this exchange under control by the surgeon’s foot pedal. The advantage of this technique is that it avoids the backward displacement of the retina that could occur in other types of exchanges when we are dealing with large tears or detachments with giant tears (Figs 27A and B).

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Figures 27A and B  (A) Direct perfluorocarbon-silicone oil exchange. This always generates a layer of saline that has to be aspirated (yellow arrow). To do this, the probe is positioned at the meniscus formed at the perfluorocarbon liquid-silicone interface; (B) Once the saline meniscus has been removed, the silicone fills the entire eye cavity as the perfluorocarbon is removed

Emulsification of the Silicone Oil An emulsion of oil in water is produced by a fall in the surface tension of the bubble of oil. This decrease in surface tension is usually the result of the deterioration of the chemical properties of the oil over time. However, other factors such as viscoelastic agents or blood remains, fibrin or new hemorrhages, can contribute to an early drop in surface tension. Emulsification is dangerous because the small drops or micelles of oil can penetrate the subretinal space, obstruct the trabeculae and alter the corneal equilibrium. In normal conditions, this phenomenon usually occurs 3–6 months after the oil has been implanted in the vitreous cavity. As already outlined, there is a nonlinear direct correlation between the molecular weight, density, surface tension and stability of the oil. Oils of 5,000 cSt are more stable and show a greater durability than oils of up to 4,000 cSt. However, no evidence exists for this correlation in oils of viscosity greater than 5,000 cSt. Accordingly, for short-term tamponade we use oils of 1,000 cSt because they are easy to inject and extract, while for longer periods of tamponade, we use oils of 5,000 cSt.

Indications of Silicone Oil Tamponade ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

RD with PVR C3-D Severe PDR RD due to macular hole Giant tears Chronic uveitis with marked hypotony

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151 ƒƒ Infectious retinitis ƒƒ Endophthalmitis ƒƒ Ocular trauma

Inferior Peripheral Iridectomy An inferior iridectomy may be performed for prophylactic purposes if it is anticipated that the silicone oil could cause pupil block. This will allow the aqueous humor to flow from the ciliary processes to the anterior chamber unimpeded by the silicone, which will always remain in the most superior zone (given its lower density than water). An inferior iridectomy is especially indicated in aphakic eyes, in which the silicone bubble itself can impair the circulation of aqueous humor to the anterior chamber, and pseudophakic eyes due to the closeness between the iris and the IOL with the risk of their positioning one in apposition to the other. There is also a risk of pupil block in patients with an IOL implanted in the posterior chamber, with scarce capsular support, in which resistance to the push of the oil is much lower. The inferior iridectomy can hinder the entry of oil in the anterior chamber and its toxic effect on the corneal endothelium. Also for this reason we prefer to perform an iridectomy in eyes that show deteriorated physical barriers to the passage of silicone oil to the anterior chamber. For instance, when during vitrectomy or exchanges the bubbles of air or gas are capable of penetrating the anterior chamber from the vitreous space, this suggests that the silicone oil could also do so. For an inferior iridectomy, we recommend the use of the vitreotome at high aspiration and low cutting speed. With the eye filled with physiological saline (if filled with air this would pass to the anterior chamber after the iridectomy), we approach the mouth of the vitreotome to the lower base of the iris, a gentle suction and once the iris is trapped at the vitreotome mouth, we introduce the cutting function. Iridectomies should be large otherwise they tend to reclose.

Removal of Silicone Oil Silicone is a temporary tamponade agent and should therefore be removed before any complications arise such as those mentioned earlier. For many years, the 20-gauge approach has been our method of choice to extract silicone oil, but as mentioned in this chapter, the improvements introduced in the new vitrectomy platforms allow for excellent removal of silicone oil through a 23-gauge port. First we place a temporal infusion line and further two superior ports for the extrusion cannula and endolight. The infusion line is opened at some 20 mm Hg, the dense fluid extraction pump is started, and we then watch how the silicone is drawn to the extrusion pipe. The cannula is always kept in the silicone bubble, otherwise the syringe would fill with saline and we would have to empty it to continue extracting the silicone (Fig. 28). We then

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Figure 28  Syringe with a 20-gauge needle used for injecting/extracting fluids. The syringe is connected to the vitreotome’s infusion pump. To extract fluid, make sure the plunger is initially pushed in

observe the bubble diminishing in size until it disappears from the pupillary area and then rotate the eye such that the force of the saline expels the small remains of silicone through one of the sclerotomies. Surgery is completed by revising the retina and checking if it is flat. If we have any doubts as to whether it will remain in place, laser treatment can be applied to any suspected zones using an illuminating laser probe. If the patient is aphakic, we can extract the silicone through the anterior chamber by placing a 25-gauge infusion line and by making an incision in the sclerocorneal limbus; we can observe how the silicone emerges pushed by the saline (Fig. 29).

CLOSURE AFTER SURGERY When surgery is complete, the entire retinal periphery should be revised for tears, which should be appropriately treated. This is undertaken by placing a scleral plug in one of the sclerotomies and reducing the IOP to avoid the risk of incarceration of the vitreous. Using the wide-field system and with the help of scleral indentation, we carefully revise the entire peripheral retina and treat any tear detected directly with the laser probe. Treatment can be followed by

Figure 29  Extracting silicone through a limbal incision in an aphakic patient. Through a 25-gauge port, pressure is infused pushing the silicone through the corneal incision, which has been half-opened with the help of a cannula

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153 fluid/air exchange and the air left in the eye as a preventive measure. If we find no tears in the retina, we then move onto revising the sclerotomies to check for incarcerated vitreous using the active vitreotome and ensuring there is no remaining vitreous. When working with 23-gauge, incomplete fluid/ air exchange is possible making use of the floatability of air in water and its pushing power to better seal the sclerotomy avoiding the need for sutures. However, if the trocars have been manipulated extensively during surgery or if we suspect that the sclerotomies will not self-heal, we recommend their transconjunctival suture. When working with 20 gauge, the sclerotomies are sutured by planes using 8-0 vicryl for the sclera and bipolar cautery or vicryl 8-0 for the conjunctiva.

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154 17. Farah ME, Maia M, Rodrigues EB. Dyes in ocular surgery: principles for use in chromovitrectomy. Am J Ophthalmol. 2009;148(3):332-40. 18. Rodrigues EB, Maia M, Meyer CH, et al. Vital dyes for chromovitrectomy. Curr Opin Ophthalmol. 2007;18(3):179-87. 19. Engelbrecht NE, Freeman J, Sternberg P, et al. Retinal pigment epithelial changes after macular hole surgery with indocyanine green-assisted internal limiting membrane peeling. Am J Ophthalmol. 2002;133(1):89-94. 20. Gandorfer A, Haritoglou C, Gass CA, et al. Indocyanine green-assisted peeling of the internal limiting membrane may cause retinal damage. Am J Ophthalmol. 2001;132(3):431-3. 21. Rodrigues EB, Meyer CH, Mennel S, et al. Mechanisms of intravitreal toxicity of indocyanine green dye: implications for chromovitrectomy. Retina. 2007;27(7):958-70. 22. Gandorfer A, Haritoglou C, Kampik A, et al. Retinal damage from indocyanine green in experimental macular surgery. Invest Ophthalmol Vis Sci. 2003;44(1):316-23. 23. Lee JE, Yoon TJ, Oum BS. Toxicity of indocyanine green injectect into the subretinal space: subretinal toxicity of indocyanine green. Retina. 2003;23(5):675-81. 24. Da Mata AP, Burk SE, Foster RE, et al. Long-term follow-up of indocyanine green-assisted peeling of the retinal internal limiting membrane during vitrectomy surgery for idiopathic macular hole repair. Ophthalmology. 2004;111(12):2246-53. 25. Haritoglou C, Gandorfer A, Schaumberger M, et al. Light-absorbing properties and osmolarity of indocyanine-green depending on concentration and solvent medium. Invest Ophthalmol Vis Sci. 2003;44(6):2722-9. 26. Haritoglou C, Gandorfer A, Gass CA, et al. Histology of vitreoretinal interface after staining of the internal limiting membrane using glucose 5% diluted indocyanine and infracyanine green. Am J Ophthalmol. 2004;137(2):345-8. 27. Balaiya S, Brar VS, Murthy RK, et al. Comparative in vitro safety analysis of dyes for chomovitrectomy: indocyanine green, brilliant blue green, bromophenol blue, and infracyanine green. Retina. 2011;31(6):1128-36. 28. Melles GR, de Waard PW, Pameyer JH, et al. Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery. J Cataract Refract Surg. 1999;25(1):7-9. 29. Stalmans P, Van Aken EH, Melles G, et al. Trypan blue not toxic for retinal pigment epithelium in vitro. Am J Ophthalmol. 2003;135(2):234-6. 30. Farah ME, Maia M, Furlani B, et al. Current concepts of trypan blue in chromovitrectomy. Dev Ophthalmol. 2008;42:91-100. 31. Enaida H, Hisatomi T, Goto Y, et al. Preclinical investigation of internal limiting membrane staining and peeling using intravitreal brilliant blue G. Retina. 2006;26(6):623-30. 32. Haritoglou C, Schumann RG, Kampik A, et al. Heavy Brilliant Blue G for internal limiting membrane staining. Retina. 2011;31(2):405-7. 33. Schmid MK. A new method to improve dye application to the retinal surface during vitrectomy. Retina. 2011;31(4):801-3. 34. Kunikata H, Abe T, Murata H, et al. Hypothermia of 8 degrees C protects cultured retinal pigment epithelial cells and retinal ganglion cells against trypan blue toxicity. Am J Ophthalmol. 2006;141(4):754-6. 35. Peyman GA, Cheema R, Conway MD, et al. Triamcinolone acetonide as an aid to visualization of the vitreous and the posterior hyaloid during pars plana vitrectomy. Retina. 2000;20(5):554-5.

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155 36. Kimura H, Kuroda S, Nagata M. Triamcinolone acetonide-assisted peeling of the internal limiting membrane. Am J Ophthalmol. 2004;137(1):172-3. 37. McCuen BW, Bessler M, Tano Y, et al. The lack of toxicity of intravitreally administered triamcinolone acetonide. Am J Ophthalmol. 1981;91(6):785-8. 38. Chang S. Low viscosity liquid fluorochemicals in vitreous surgery. Am J Ophthalmol. 1987;103(1):38-43. 39. Charles S, Wang C. A motorized gas injector for vitreous surgery. Arch Ophthalmol. 1981;99(8):1398. 40. Brucker AJ, Hoffmam ME, Nevyas HJ, et al. New instrumentation for fluid-air exchange. Retina. 1983;3(2):135-6. 41. Charles S. Vitrectomy Microsurgery. Philadelphia: Williams and Wilkins; 2002. pp. 89.

chapter 7

Pars Plana Lensectomy Carlos Mateo, Anniken Burés

INTRODUCTION Pars plana lensectomy (PPL) is a surgical technique employed to extract the lens using the same entry sites as used for vitrectomy. It is not the first choice technique when dealing with a cataract surgery or combined surgery (lens extraction and vitrectomy) in those cases in which the anterior vitreous or anterior hyaloid does not have a significant pathologic role. However, PPL is an excellent technique in all those cases that require a thorough management of the anterior vitreous.

SURGICAL TECHNIQUE Since PPL is practically always used in combination with pars plana vitrectomy, the first step would be to place the infusion cannula in the pars plana. After this, some surgeons prefer to perform a central vitrectomy to avoid interference of the anterior vitreous with the phacofragmenter in case of premature rupture of the posterior capsule. However, we prefer to start with the lensectomy before proceeding with the vitrectomy, since this provides greater stability to the lens during lensectomy. To perform the PPL, two sclerotomies are performed, located at 10 o’clock and 2 o’clock positions. The right hand is usually employed to use the phacofragmenter whereas the left hand holds an intralenticular infusion cannula at the same pressure as the previously placed and opened infusion cannula (after confirming its correct placement into the vitreous cavity). The intralenticular infusion maintains the lens bag open during the surgery, avoiding the collapse of the bag and therefore minimizing the risk of damaging the capsules with the phacofragmenter (Fig. 1).

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Figure 1  The intralenticular infusion maintains an open lens bag during the surgery, which avoids the collapse of the bag and minimizes damage to the capsules

It should be mentioned that, in spite of being a personal preference, some surgeons do not use this kind of infusion because of the risk of inadvertent damage to the posterior capsule, which is clearly less resistant than the anterior capsule. Also, in the cases of traumatic cataract, due to intraocular foreign body, it is better not to use the intralenticular infusion since the fluid turbulences could tear further, the already damaged capsules. The two sclerotomies are performed at 3–3.5 mm distance from the sclerocorneal limbus directing the microvitreal blade toward the center of the lens nucleus. The phacofragmenter is introduced following the same track and after it the intralenticular infusion is performed (Figs 2A to D). The first maneuver is to place the tip of the infusion cannula in front of the phacofragmenter and to perform an initial aspiration with or without ultrasound (depending on the hardness of the lens). This is done in order to unblock the tip of the phacofragmenter, since lens material enters the tip when introducing the phacofragmenter into the lens (Fig. 2A). Once we observe that the infusion cannula is permeable (the capsular bag remains open and a certain degree of hydrodissection of the lens is observed), fragmentation and aspiration of the central and harder lens material are performed. The “miner” technique (St Charles) consists of introducing and extracting the tip of the phacofragmenter in different directions to fragment the nucleus and then aspirate it (Fig. 2B). If some whitish material appears around the tip of the phacofragmenter, the procedure must be interrupted immediately (Fig. 3). This material is a sign of heating of the phacofragmenter and secondary lens protein coagulation. The heating of the phacofragmenter occurs when the tip is blocked and thus cannot be refrigerated. Simultaneously, we may observe a burn at the sclerotomy site, not only exteriorly, but also on the inside. When this occurs, the instrument is pulled out and cleaned, to remove the lens material blocking the tip. The peripheral part of the lens can be removed safely with the vitreous cutter (Fig. 2C). On many occasions we may observe that once the lens nucleus is extracted, the posterior capsule is torn and vitreous fibers flow into the anterior chamber. At this point, the vitreous cutter is cutting lens material as well as vitreous

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Figures 2A to D  (A) To ensure that the tip of the phacofragmenter is unblocked, an initial aspiration is performed by placing the tip of the infusion cannula in front of the phacofragmenter; (B) Consecutive introduction and extraction of the tip of the phacofragmenter fragments the nucleus of the lens, making it easier to aspirate; (C) Cortical lens material can be managed with the vitreous cutter, which is also used to remove the anterior vitreous gel, once the posterior capsule is open; (D) The anterior capsule is polished using the vitreous cutter at a low aspiration rate and performing fast polishing movements

and anterior hyaloid, minimizing peripheral vitreoretinal traction. From this moment onward, the intralenticular infusion is no longer necessary and can be pulled out. The remains of the posterior capsule are cut up to the pre-equatorial area placing the port of the vitreous cutter downward. After this, the anterior capsule is polished using the vitreous cutter with the cutting turned off and with a low aspiration rate (100–150 mmHg) performing fast polishing movements (Fig. 2D). Lens material that falls into the vitreous cavity is easily removed during vitrectomy.

ADVANTAGES OF PARS PLANA LENSECTOMY Compared to standard phacoemulsification by the anterior approach, the main advantages of pars plana lensectomy combined with vitrectomy are: ƒƒ The anterior chamber remains sealed throughout the entire procedure, therefore no corneal alterations or changes in the pupil size occur (in those cases where the anterior capsule remains undamaged) ƒƒ It allows full access to the anterior vitreous and anterior hyaloid ƒƒ Despite pressure fluctuations during the surgical procedure, it is neither necessary to introduce viscoelastic material nor to suture the cornea since the anterior chamber remains sealed during the surgery.

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Figure 3  A rapid and whitish opacification of the lens during pars plana lensectomy is a sign of protein coagulation due to the high temperature of the phacofragmenter tip. This means that the tip of the phacofragmenter is blocked and is not aspirating efficiently, making it impossible for the tip to cool down

PARS PLANA LENSECTOMY INDICATIONS Vitreoretinal Proliferation Vitreoretinal proliferation (VRP) after retinal detachment surgery, particularly when the anterior vitreous is clearly involved, is a major indication for PPL, since it is almost impossible to treat the contracted anterior vitreous and membranes without damaging the lens (Fig. 4). On the other hand, many of these patients show variable degrees of lens opacities due to the previous surgeries and tamponading elements used. When maintaining the anterior capsule intact throughout the surgery, PPL minimizes the risk of intraoperative myosis and allows an excellent visualization and accessibility, facilitating a thorough removal of the anterior vitreous and anterior hyaloid which, if left untreated, can promote secondary postoperative hypotony. At the end of the surgery, the surgeon must choose between leaving the anterior capsule intact or removing it. Whereas some surgeons prefer to remove the capsule to prevent a hypothetical contraction of the latter that could cause traction of the ciliary processes and thus postoperative hypotony, others prefer to leave the capsule in order to keep a separation between anterior and posterior compartments and thus avoiding any damage of the anterior segment structures due to the tamponading elements. If one chooses to remove the anterior capsule, it is important to perform a peripheral iridotomy that should be superior when employing a gas or low

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Figure 4  Due to the convexity of the lens, damage to the posterior capsule is almost constant when dealing with anterior vitreoretinal proliferation

density silicone oil and inferior when using high density silicone oil. If the anterior capsule is not removed, the capsule will be progressively opacified due to the fibrin deposition secondary to the rupture of the blood-retinal barrier present in VRP (Fig. 5).

Perforating Ocular Trauma with or without Intraocular Foreign Body Depending on how the lens penetrates the eye, an intraocular foreign body may or may not damage the lens. When the lens is damaged, because of a penetrating foreign body or due to an open globe injury, the hydration of the lens material makes it almost impossible to ascertain whether the posterior capsule is torn.

Figure 5  At the end of the surgery, the surgeon chooses whether to remove all the capsular remnants or leaving the anterior capsule, which will facilitate a secondary intraocular lens implant

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161 For this reason, phacoemulsification by the anterior approach is usually not recommended due to the high risk of complications. If the posterior capsule is torn, vitreous gel may appear between the lens material and this vitreous should under no circumstance be managed with phaco tip, since the risk of placing traction over the peripheral retina and thus producing retinal tears and retinal detachment is high (Figs 6A to F). In these particular cases, lensectomy is, in our opinion, the safest and most rational way of managing the cataract as well as the vitreoretinal tractions, allowing the extraction of the intraocular foreign body (if present) by the anterior approach. There are some technical differences in these cases compared to other lensectomy indications: ƒƒ The use of an intralenticular infusion cannula may be detrimental, since the fluid currents could tear even more the already damaged capsules ƒƒ Whenever possible, it is important to keep as much of the anterior capsule as possible, since it will serve as a support for an intraocular lens. It is quite useful to inject viscoelastic material into the anterior chamber in those cases with corneal laceration that is still not sealed in spite of the sutures. With this, we avoid damaging the residual capsular support due to the fluid currents (Fig. 7A).

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Figures 6A to F  (A) Traumatic cataract due to penetrating ocular trauma with an iron wire. In these cases, it is almost impossible to ascertain whether the posterior capsule is torn or not; (B) Manual aspiration of the cortical masses; (C) Rupture of the posterior capsule and vitreous material inside the lens; (D) Pars plana lensectomy using the vitreous cutter allows complete removal of both the vitreous gel and the lens material; (E) Polishing of the anterior capsule; (F) Intraocular lens implantation in the posterior chamber

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162 ƒƒ The vitreous cutter is usually enough to perform lensectomy in these cases,

both because of the previous hydration of the lens, which makes it softer, and because the patients tend to be younger (Fig. 7B). Using the vitreous cutter will also avoid unnecessary vitreoretinal traction in those cases where there are residual vitreous fibers mixed with the lens material. It is also important to perform a careful polishing of the anterior capsule avoiding extending any possible tears (Fig. 7C). ƒƒ It is preferable to extract any intraocular foreign body through the limbus instead of the sclerotomy. The risk of producing an uncontrolled retinal tear is much higher when extracting the intraocular foreign body through the pars plana (Fig. 7D). After extracting the intraocular foreign body through the limbus, the same incision can be used to implant an intraocular lens whenever there is enough capsular support.

Proliferative Diabetic Retinopathy It is widely known that cataract is more common and develops earlier in diabetic patients. In most cases, phacoemulsification and intraocular lens implantation in the capsular bag is the first choice technique when performing combined surgery in proliferative diabetic retinopathy (PDR). However, phacoemulsification can show some difficulties when performed right before the vitrectomy:

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Figures 7A to D  (A) Viscoelastic material is injected into the anterior chamber to avoid fluid currents through the corneal laceration, which would tear even more a previously damaged anterior capsule; (B) Lensectomy is performed with the vitreous cutter to avoid peripheral retinal tractions; (C) Polishing of the posterior side of the anterior capsule; (D) The intraocular foreign body is extracted by an anterior approach, before implanting an intraocular lens

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163 ƒƒ Phacoemulsification and the capsulorrhexis, in particular, are more difficult

in those cases with vitreous hemorrhage due to the poor fundus reflex

ƒƒ Myosis during surgery is more common in diabetic patients as is bleeding

from small vessels into the anterior chamber, which may reduce visualization

ƒƒ When dealing with retinal vascular proliferations, intraocular pressure needs

to be raised to avoid bleeding. This requires a completely sealed anterior chamber, thus corneal sutures are usually necessary, which can cause residual astigmatism and corneal striae that reduce visualization ƒƒ The intraocular lens can interfere in the correct visualization of the retinal periphery. This is especially important when dealing with peripheral preretinal neovessels ƒƒ Posterior synechiae from the iris to the capsulorhexis and fibrin in the anterior chamber are more frequent in diabetic patients. Pars plana lensectomy offers some advantages in severe cases of PDR: ƒƒ The anterior chamber remains sealed throughout the entire surgical procedure, which reduces the risk of myosis and thus reduces the risk of bleeding into the anterior chamber ƒƒ Both central and peripheral visualization are excellent since there is no interference of an intraocular lens ƒƒ When implanting the intraocular lens into the sulcus, the risk of synechiae formation is less since there is no contact between the iris and the capsule. In spite of its potential advantages, pars plana lensectomy in diabetic retinopathy is only considered in severe cases with peripheral retinal neovessels that need to be treated and which require excellent visualization of the periphery throughout the surgical procedure.

Chapter 8

Basic Endoscopic Vitrectomy Vicente J Chaqués-Alepuz, Enrique V López-Sánchez

BASIC EQUIPMENT FOR ENDOSCOPY The equipment we need for endoscopic surgery of the ocular globe can be divided into two main groups (Fig. 1): ƒƒ The endoscope itself (hand piece and probe) (Fig. 2) ƒƒ The illumination system, the video system and the laser source. Essentially, the video system for endoscopy comprises (Fig. 3): –– a video camera, –– a monitor or screen and –– a light source. The images “captured” by the endoscope are transmitted to the charge coupled device (CCD) chips of the video camera and then to the monitor. These recorders can have one or three analog or digital chips. Usually they have three digital CCD chips. The captured images are stored in an image-capturing device such as a video recorder, DVD or hard disk (Fig. 4). Currently, hard drives are the preferred storage devices. The best and most used light source is the xenon

Figure 1  Diagram showing the components of an endoscope system used in ophthalmology

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Figure 2  Ophthalmologic endoscope. Hand piece and intraocular straight piece

Figure 3  Integrated module for ocular endoscopy with image and illumination

Figure 4  Video recorder and monitor module

light. As a laser source, any optic fiber laser used in ophthalmology can be combined with endoscopy for intraocular treatment. In practice, semiconductor diode lasers emitting wavelengths of 532 nm (green) and 810 nm (close to infrared) are the standard sources used.

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TECHNICAL ASPECTS: VISUALIZATION Most endoscopy “systems” are essentially a “pack” containing these individual components (image capturer, video camera, video monitor, image storing device, illumination and laser source) (Figs 5 and 6). To protect the surgeon and assistants from the detrimental effects of the laser, we usually place a filter that blocks the laser’s specific wavelength (532 or 810 nm) in the microscope’s optical path. Although obvious, we should mention that if the laser beam is only observed on the monitor screen and not through the microscope then a laser filter is not needed.

Figure 5  Complete set-up for endoscopy including a monitor, video recorder, light and image source, and 810 nm laser diode

Figure 6  Probe with three functions (imaging, illumination and laser)

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167 Fiber optic endoscopes are indisputably the most widely used in ophthalmology practice. In these, the image guide is comprised of a beam of thousands of quartz fibers. Each individual quartz fiber provides a tiny fraction of the overall image called a pixel. The first marketed ophthalmologic endoscope used an image guide of 3000 pixels while the current standard is 10,000 pixels and models exist of 17,000 pixels. This fiber optic system of image capture and transfer produces a “honeycomb” effect on the monitor when the image is focused. Although annoying at first, the surgeon eventually gets used to this effect, which indicates maximum focus and resolution. It should be noted that the number of pixels is not the only determinant of the quality of the image. This depends on other factors such as: the viewing field (currently 110°) ƒƒ the field depth, or the distance across which the image is focused: from 0.75 to 40 mm ƒƒ the illumination angle: ideally 110° Another important feature is the lack of stereopsis. This is because only a single image is captured. However, there are a few tricks to obtain some degree of pseudostereopsis. Wide-field endoscopes of 110° can offset this deficiency by exchanging stereopsis for a panoramic view. The surgeon can also guide himself/herself using certain visual details such as the locations of the instruments within the globe or the effects of such instruments on adjacent ocular structures.

Image Rotation The image guide occupies a specific position within the endoscope structure. The orientation of the image is determined by the relative position of the distal and proximal ends of the image guide. According to the relative position of these extremes, we will perceive a well-orientated upright image or an obliquely orientated or even inverted image. At many points during the surgery, it is not excessively important to have real information about the position of the image since we can equally see the intraocular structure of interest or apply laser treatment to a structure without worrying about its orientation. However, in practice it is best that the image orientation matches the real anatomy since this is reassuring and simplifies the surgical maneuvers. In other words, in intraocular endoscopically guided surgery it is of great help if we can maintain the correct position of the superior and inferior part of the image. Changing the orientation of the image is simple: the surgeon only has to rotate the endoscope’s hand piece between the fingers. This rotation can be conducted before the endoscope is introduced in the eye or after it has been introduced in the surgical space (Figs 7A and B).

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Figures 7A and B  (A) Real view of ora serrata (OS), ciliary processes (PC), ciliary sulcus (SU) and (B) Vision with rotation 90º

Thus, the first step before introducing the endoscope in the eye is to orientate the endoscope image on the monitor. This is done by focusing the endoscope on any object or point of the surgical field and swivelling the probe with the fingers.

Image Artifacts If we consider the large number of optical interfaces existing along the endoscopic path, it becomes obvious that there is every chance that the final image with which the surgeon needs to work will be altered. The build-up of deposits at the tip of the endoscope can lead to a blurred image or to black spots of different sizes. Just a small amount of blood or particles can markedly compromise vision. To resolve this problem it is usually sufficient to clean the endoscope tip with a dry sponge or cotton bud. The proximal end of the probe can similarly be affected by the build-up of remnants creating a diffuse haze or black spots. The most common cause of this problem is the powder from the gloves of the surgery team. The remedy is the same as described above. Less frequently dust or other deposits that accumulate at the distal or proximal end of the magnifying, focusing complex or the filter that connects the endoscope to the camera’s CCD chips, may also give rise to a degraded image. This problem may be resolved by using a lens cleaning solution or a stream of compressed air. Fiber optic endoscopes contain bundles of up to 17,000 small glass tubes. Any physical damage along their length has the consequence of a “broken” pixel, which appears as a large irregular area of well-defined image loss. This artifact cannot be eliminated without reconstructing the endoscope’s imaging system and it is more expensive to repair this defect than to buy a new probe. Hence, if the scotoma created by a loss of pixels does not impair the surgeon’s vision, the endoscope can still be used.

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169 The surgeon should control the intensity of illumination to obtain the best image possible. The closer the tip of the endoscope to the tissue, the less light is needed. Conversely, the further away the tip the greater will be the field of view and more light is needed. If the intensity of light is too high, the video image will be washed out or faded while insufficient light will generate a dark image. With some ophthalmologic endoscopes, the surgeon controls the intensity of light with a pedal to avoid this problem. A further problem that has not yet been resolved is glare produced on the video screen caused by the light reflected off the metal surface of the vitreotome hand piece.

Technical Tips for the Beginners Since the endoscope image is produced at the distal tip of the instrument, this part of the instrument cannot be seen. Thus, the instrument should be advanced within the eye according to what the endoscope “sees”. The surgeon should learn to recognize the endoscopic features of the eye, which may look different to when viewed by conventional means. Certain visual cues can be obtained from the surrounding anatomy so that the endoscope and other instruments can be manipulated in the eye. This brings us to the second technical tip, which is to watch the operation in progress on the video screen rather than through the operating microscope. For some people, this transition can be difficult (Fig. 8). Beginners should try to avoid surgery on phakic eyes to prevent the risk of damaging the crystalline lens generating a traumatic cataract. A relatively simple case should be selected such as chronic vitreous hemorrhage. Early in the learning curve, it is useful to simultaneously work with double illumination from both the microscope and endoscope. To do this, we use the light provided by the endoscope for endoillumination and then simultaneously

Figure 8  Relative positions of the operating surgeons and surgical equipment. The surgeons are watching the video on the screen rather than through the microscope

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170 watch out for visual cues through the operating microscope. This tactic can speed up the learning process.

ENDOSCOPIC POSTERIOR VITRECTOMY: BASIC CONCEPTS AND INDICATIONS There are two basic benefits of endoscopic guidance during intraocular surgery: visualization through opaque media and access to anatomical structures that could not otherwise be seen. The first of these refers to visualization of the posterior segment when the conditions of the anterior pole prevent this, as occurs when there is corneal opacification, a flat anterior chamber, the presence of blood in the anterior chamber, a miotic pupil, opacification of the crystalline lens or the posterior capsule, or the presence of a cyclitic membrane. The image obtained by the endoscope assisted by the video monitor avoids these obstacles by definition since the endoscope tip is introduced through the pars plana. In cases of opaque corneas, there is no need for penetrating keratoplasty or a temporary keratoprosthesis. The second benefit conferred by the endoscope has to do with its capacity to provide images of structures that are inaccessible using other techniques. Thus, posterior iris, sulcus and ciliary body cannot be viewed using the operating microscope, and structures such as the pars plana and retinal periphery cannot often been clearly observed, which can sometimes preclude certain surgical procedures. It is in these circumstances, when the endoscope can be of most help. In addition, the endoscope can inform us of the state of the posterior pole as well as of the presence of optic nerve disk atrophy, which will limit the patient’s vision and visual outcome despite conducting flawless surgery. Also, before finishing surgery we can inspect the peripheral retina and the sclerotomies, especially in aphakic or pseudophakic eyes. The use or not of the endoscope and its combination with the operating microscope is the surgeon’s decision since it has to be recognized that its resolution is still not comparable to that of the operating microscope and we lack stereopsis. Depending on the eye condition and the point during surgery, the use of one or other visualization system will be best since at certain times during an operation we will need to use both hands and let go the endoscope hand piece, for instance, while looking through the microscope.

Surgeon’s Position When performing endoscopic eye surgery, the surgeon is usually positioned at the head of the operating table. The endoscope system’s video screen should be approximately 1 metre from the surgeon for good visualization, although its position depends on the preference of the surgeon and that of the rest of the surgical equipment. If the screen is too far away, it may be difficult to see the details of the image (Fig. 8).

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Image Size and Lighting Magnification, visual field and illumination vary with the distance between the tip of the endoscope and the target tissue. For intraocular endoscopy, it is important to know how image and visual field size change. As the endoscope tip approaches the zone to be treated, the size of the image will increase and the visual field will be diminished, and vice versa as we move away from the zone, the image will get smaller but we will see across a wider field. Illumination requirements are such that we will need less light as we approach the treatment zone and more light as we move away from this zone.

Blurred Image During the course of endoscopic surgery, a blurred image can be quickly produced but this is nevertheless easy to remedy. This is a frequent problem even when using an endoscope at other body sites. In intraocular surgery, “fog” appears mostly during fluid/air exchange, when the warm balanced saline solution is replaced with cold air or gas owing to condensation on the tip of the endoscope, as occurs on the posterior side of an intraocular lens in similar circumstances. Fog can also occur when an active hemorrhage is produced and when dense deposits exist such as in infectious ophthalmitis. When a foggy image occurs, the most useful measure is to withdraw the tip of the endoscope towards the entrance sclerotomy. Usually, a film of liquid sticks to the endoscope rod and this will dissipate and spread to the tip lens clarifying the image. This maneuver can be repeated as many times as needed. If this does not work, another option is to advance the tip of the endoscope until it makes contact with any residual intraocular fluid—we will see the fog quickly vanish although it often quickly reappears as the endoscope tip is withdrawn from the fluid meniscus. Another option is to use an instrument with a soft tip, such as a brush or extrusion cannula, to help us remove the remains from the endoscope tip without the need to withdraw it from the globe. Finally, if all else fails, the instrument is removed from the eye and carefully cleaned with a dry cloth, cotton bud or sponge.

COMPLICATIONS OF VITREORETINAL SURGERY THAT CAN BE AVOIDED BY ENDOSCOPY Vitreous Incarceration Many surgeons understand the importance of examining the inner aspect of a sclerotomy before finalizing the surgical procedure. However, using the

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172 operating microscope, this cannot usually be well visualized. Many articles exist in the literature describing possible problems caused by sclerotomies. One of the main advantages of endoscopic surgery is the possibility of examining in great detail the state of both prior and current sclerotomies, and resolving the problems caused by these. In most sclerotomies, incarcerated vitreous is easily observable (Fig. 9). Although many surgeons think that cutting the collapsed vitreous through the sclerotomy incision may be sufficient to resolve the problem, endoscopy has shown that this strategy is not the solution. Thus, the vitreous incarcerated on the internal lip of the sclerotomy cannot be detached by cutting the vitreous herniated towards the outside of the incision. The only way to resolve this problem is to use a mechanical vitreous cutter to cut and suction the vitreous adhered to the inner side of the incision in the ocular wall. It is, however, true that this maneuver is difficult or impossible to complete. The vitreous base can be very dense and sticky such that the vitrector is unable to cut it. Most often this situation does not affect the outcome of surgery and vitrectomy has a high success rate.

Controlling Intraoperative Bleeding Occasionally, bleeding can occur from the inner aspect of the sclerotomy and may even persist during the entire procedure. Sometimes cautery or an increase in intraocular pressure is insufficient to resolve this problem. Bleeding areas can be easily detected using the endoscope and direct cautery, or pressure exerted by the tip of the instrument on the point of bleeding added to increase the intraocular pressure are often sufficient to control the situation.

Figure 9  Vitreous incarceration is a complication of vitreoretinal surgery that can be easily seen using an endoscope

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TECHNIQUES AND MANEUVERS OF VITRECTOMY AND ENDOSCOPY All the maneuvers conventionally performed under visualization through the microscope can be completed with lesser or greater difficulty using endoscopic visualization. Here, we will only comment on the strategies that are best performed by endoscopy.

Vitrectomy The endoscope is introduced through the sclera maintaining a panoramic view. Through the opposite sclerotomy, the vitreotome is introduced. With the endoscope still, the vitrector is manipulated until it appears in the middle vitreous. The cutting and aspiration mechanism is started. We should avoid moving the endoscope to maintain the field of view. The vitreous looks like an opaque white cloud and this appearance gradually disappears as we eliminate it. As the vitrectomy proceeds, the vitreotome gets closer to the endoscope; this results in magnification of the vitrectomy hand piece rod (Figs 10A and B). The surgeon is provided with some degree of 3 dimensional orientation such that, with this movement, inadvertent damage to ocular structures can be avoided. This procedure is conducted until the remaining vitreous has been removed; the endoscope and vitreotome can be exchanged hands to aid visualization of all the residual vitreous. To enable working closer to the retina, we move the endoscope towards the retina followed by the vitreotome through a small approximation movement. This maneuver is repeated until the surface of the retina has been reached. The principles of vitrectomy are similar to those of vitrectomy under the microscope; as we approach the retina we should increase the cutting speed and lower the aspiration power to control flow and traction on the retinal tissue.

Figures 10A and B  Relation between the endoscope tip and the vitreotome. A panoramic view is maintained using the endoscope while the vitrector is advanced towards the endoscope. (A) At first the vitrector is far away and appears small; (B) As the vitrector approaches the endoscope it appears larger

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174 At any point during the surgery, the surgeon can check the adequate progress of surgery by visualization under the microscope, controlling the appropriate positions of the instruments. Only when microscope observation is impaired by the opacity of the media does the endoscopy technique reach its full potential, allowing the surgeon to calmly continue with the procedure. To dominate the technique, the endoscope should be regularly used alongside the microscope, such that this mode of working can be selected when the situation demands.

Membranectomy The removal of membranes is by far the most challenging endoscopic surgery procedure and requires stereoscopic vision. Despite this, a 2 dimensional image may be sufficient for a good membranectomy except in cases of fine dissection, such as the presence of a premacular membrane, since the risk of inadvertent damage may be high. It is not the same to remove a membrane from the optic nerve surface or a more peripheral membrane as in proliferative diabetic retinopathy.

Fluid-Air Exchange It is relatively frequent that the microscope image is poor in complicated cases at the end of the surgery because of corneal opacity, miosis or condensation of drops behind an intraocular lens. This situation can be particularly frustrating for the surgeon. The exchange maneuver can be performed under endoscopic guidance avoiding the problems just mentioned. For the exchange, we introduce a soft silicone-tipped extrusion cannula through one of the sclerotomy incisions and through the other sclerotomy we insert the endoscope maintaining a panoramic view with good illumination. The hand piece should be well orientated with respect to the ocular anatomy. The bubbles of air will enter the eye and it will be possible to visualize the air/ fluid meniscus.

Endophotocoagulation Endophotocoagulation is certainly one of the most common procedures in vitreoretinal surgery. When performed under the operating microscope we need two hands; one for the laser probe and one for endoillumination. With these instruments, endolaser treatment can be well applied especially in posterior zones, but as we work more anteriorly, it becomes difficult or even impossible to reach the ciliary body. With the endoscope in only one hand we have available an image, endoillumination and laser probe, and can simultaneously use these three functions for effective photocoagulation throughout the entire globe even in circumstances of media opacity (Fig. 11).

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Figure 11  Endoscopic photocoagulation

Pars Plana Lensectomy The course of a lensectomy can be followed through the anterior segment with the microscope. The posterior localization of nuclear or cortical fragments along with capsule remains can be surveilled using the endoscope. In this way it is easy not to miss any crystalline lens remains that could be left in the eye, as may occur if we only use the microscope. Moreover, after removing the crystalline lens fragments the endoscope enables any iatrogenic peripheral retinal tears to be detected and if these appear, we can immediately photocoagulate them.

Capsulectomy Depending on the underlying disease, the surgeon may choose to extract the capsule remains. Although this procedure can be partially or fully conducted using the vitrector, the ideal is to use forceps to lift the edges of the capsule under endoscopic guidance. Endoscopically-guided capsulectomy is easy to perform and serves to eliminate all capsule remains without leaving behind any tissue that could act as a substrate for a potential proliferation.

Introducing Silicone Oil Under endoscopic visualization, the injection of silicone oil is an easy procedure. Normally, the endoscope is used with a wide visual field in an airfilled eye. The silicone cannula can be visualized within the eye when we start the injection process and we can watch the oil falling on the optic nerve and macula gradually filling the globe. This technique offers two advantages over injection guided by the microscope. The first is that we can visualize the procedure until the end of the filling process with the endoscope but not with the operating microscope. When the oil goes beyond the globe equator, microscopy vision of the extreme

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176 periphery is poor. In contrast, the endoscope allows revision of the periphery and the posterior iris without the need for indentation or other maneuvers, offering precise monitoring of the air/silicone interface and the desired filling. The second advantage is the immediate detection of the eventual passage of silicone oil to the subretinal space, facilitating its resolution at the moment of injection. Silicone oil does not degrade the endoscope image yet attenuates the impacts from the laser. Thus, the maneuvers we can carry out in an air-filled eye can also be undertaken in an eye filled with silicone oil.

Introducing Perfluorocarbon Liquid Generally the injection of a perfluorocarbon liquid is conducted with the eye filled with fluid and since it is heavier, it sinks towards the posterior pole creating a clear boundary between the perfluorocarbon and the balanced salt solution (Fig. 12). As more perfluorocarbon liquid is gradually injected, the subretinal fluid is displaced peripherally through the tear and the retina is flattened if there is no traction. However, if significant traction persists, the retina will not respond and will not flatten. One of the advantages of the endoscope is that the retinal flattening process can be visualized and any zones of persistent traction or gliosis can be detected. The endoscope may also be useful for the removal of perfluorocarbon liquid from the eye. Sometimes, small bubbles of perfluorocarbon liquid may be trapped in zones that are invisible to the microscope or visualization through the cornea and/or crystalline lens may have become blurred. In this situation the endoscope is of great help since it allows visualization and extraction of every last bubble of perfluorocarbon liquid.

Diabetic Retinopathy and Endoscopic Vitrectomy As proliferative diabetic retinopathy progresses, ocular proliferation gives rise to numerous problems which in turn lead to surgical indications, such as vitreous

Figure 12  Endoscopic visualization of the injection of perfluorocarbon liquid

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177 hemorrhage, premacular hemorrhage, severe diabetic retinopathy not responding to photocoagulation, tractional macular detachment, rhegmatogenous and tractional retinal detachment, anterior hyaloid fibrovascular proliferation, rubeosis iridis, etc. These diseases may be associated with opacity of the media.

Vitreous Hemorrhage The vitrectomy maneuvers, active or passive extrusion, fluid/air exchange and endophotocoagulation are those most commonly used to treat vitreous hemorrhage; all these procedures can be better performed under endoscopy making the removal of vitreous and blood more complete. Cleaning the anterior vitreous at the base of the vitreous is easier under endoscopic visualization. Similarly, in cases of recurrent hemorrhage, we can detect the presence of anterior proliferations, which we can approach or treat with the vitrector or forceps. It is also possible to more efficiently complete anterior panretinal photocoagulation.

Neovascularization of the Iris with Opacity of the Media If the patient has a dense cataract, corneal opacity, hyphema, or any other media opacity problem, the best treatment option is endoscopic photocoagulation. Substantial anterior pole opacity makes photocoagulation impossible with the visualization offered by the operating microscope. Further, the endoscope enables extensive photocoagulation. Finally, if neovascular glaucoma is already present after posterior retinal treatment, endoscopic cyclophotocoagulation can be conducted, irrespective of crystalline lens transparency. Combined endoscopic cyclophotocoagulation and panretinal photocoagulation is, in this situation, the safest and most efficient treatment option, avoiding aggressive procedures such as retinal cryotherapy or cyclocryotherapy.

Retinal Detachment Surgery Endoscopy facilitates vitrectomy when treating rhegmatogenous retinal detachment in several ways. First of all, the elimination of vitreous with blood, deposits and opacities can give rise to improved vision for the patient, assuming the retina flattens and attains good functionality. In second place, it simplifies the search for retinal tears avoiding the need for indirect ophthalmoscopy. This can be of particular help when faced with an opacified posterior capsule that impairs proper visualization of the peripheral retina. The endoscope can even easily detect retinal holes in the extreme periphery and these can be photocoagulated at the exact moment of their visualization (Fig. 13). Thirdly, fluid/gas exchange with internal drainage of subretinal fluid can be easily and quickly performed under endoscopic guidance, thus flattening the retina (Fig. 14). This maneuver

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Figure 13  Peripheral retinal tear associated with a sclerotomy incision

Figure 14  Endoscopic visualization of fluid/air exchange

is evidently safer, more controlled and more complete than external drainage. Fourthly, endoscopic endophotocoagulation in an air-filled eye with an attached retina is very simple and efficient. Moreover, it is less aggressive than transscleral cryopexy (Fig. 15) and may reduce the risk of inducing proliferative vitroretinopathy (PVR). It can also be performed without changing instruments. In fifth place, postoperative discomfort is minimal for the patient compared to extrascleral surgery, especially if a scleral buckle is used. Finally, reoperations for retinal detachment are simplified with less aggression to the ocular globe than repeat scleral surgery (Fig 16).

Proliferative Vitreoretinopathy Scleral Indentation The endoscope can be of great help for the complete removal of the anterior vitreous and its anterior and posterior adhesions. This feature can thus minimize the need for scleral indentation, at least for those surgeons who use a scleral buckle to better access the base of the vitreous.

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Figure 15  Endoscopic visualization of transscleral cryopexy

Figure 16  Retinal detachment. Tear bridged by a vessel and vitrectomy of the vitreous adhesion-traction to the flap

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Dissecting the Vitreous Base Independent of when, during the course of vitrectomy, the surgeon acts in this zone, the complete elimination of the base of the vitreous and the membrane at the posterior iris and ciliary body is essential for the successful treatment of PVR. In this region, the endoscope may be of great use given its difficult access even in the best of circumstances. For surgeons with early experience in PVR surgery with scleral indentation and lensectomy, visualization using the operating microscope can be extremely poor during this stage of surgery. The endoscope can clearly delineate the altered anatomy and its effect on neighbouring structures. Scleral depression is often used to approach areas of interest to the microscope’s visual field. With the endoscope this is unnecessary. In effect, scleral depression could relax points of vitreous adhesion to the peripheral retina, pars plana, ciliary body, crystalline lens or posterior iris, thus masking their presence while endoscopic visualization clearly identifies their existence (Fig. 17).

Endoscopic Vitrectomy for Crystalline Lens Fragments Luxated in the Vitreous Cavity The operating endoscope can be useful to remove fragments from the posterior pole but is mainly used to localize and remove remnants of the lens nucleus and cortex that are not visible with the operating microscope because of their location and that could cause glaucoma and intraocular inflammation (Figs 18 and 19). It is surprising how much crystalline lens material can become trapped at the posterior iris, sulcus and vitreous that we cannot visualize using the operating microscope. Generally, this persisting material has no important consequences and disappears without leaving sequelae but sometimes it could cause considerable damage.

Figure 17  Endoscopic peripheral retinectomy in a case of anterior PVR

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Figure 18  Endoscopic visualization of fragments of crystalline lens luxated in the vitreous in an eye with intense corneal edema. With the operating microscope, good visualization is not possible

Figure 19  Exploring the posterior zone of the iris and ciliary body with the help of the endoscope. Note the abundance of crystalline lens remains, which if not removed could cause chronic intraocular inflammation

Endoscopic Vitrectomy in Endophthalmitis In many cases of endophthalmitis, visualization conditions are insufficiently good for vitrectomy due to corneal edema and miosis. When endophthalmitis is detected early, especially as a consequence of cataract surgery, most inflammation occurs at the site of intraocular lens implant and the anterior vitreous. However, the focus of infection can be detected in the sulcus region (Figs 20A and B). Conventional visualization techniques do not allow these areas to be seen, particularly if the cornea is edematous or the pupil is miotic.

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Figures 20A and B  (A) Inflammatory and infectious deposits on ciliary processes. View of the posterior aspect of the iris and pupil, and endoillumination probe entering through the pars plana; (B) Higher magnification image of the inflammatory masses appearing in the image on the left

One of the reasons why eyes with endophthalmitis that have been successfully vitrectomized require such a long time period until the infection resolves after surgery, is perhaps that infectious and inflammatory remains persist in inaccessible areas of the eye. Endoscopic vitrectomy offers the surgeon the opportunity to detect and eliminate most of this material. In addition, when vitrectomy is needed, most eyes with endophthalmitis find themselves in the postoperative course of the surgery that provoked the infection and thus have unhealed surgical incisions. In this situation scleral indentation is not recommended. In contrast, the endoscope can provide a view of the periphery at great magnification and good resolution, and any break detected can be rapidly sealed by photocoagulation.

Bibliography 1. Ben-nun J. Cornea sparing by endoscopically guided vitreoretinal surgery. Ophthalmology. 2001;108(8):1465-70. 2. Boscher C, Lebuisson DA, Lean JS, et al. Vitrectomy with endoscopy for management of retained lens fragments and/or posteriorly dislocated intraocular lens. Graefes Arch Clin Exp Ophthalmol. 1998;236(2):115-21. 3. Ciardella AP, Fisher YL, Carvalho C, et al. Endoscopic vitreoretinal surgery for complicated proliferative diabetic retinopathy. Retina. 2001;21(1):20-7. 4. De Smet MD, Carlborg EA. Managing severe endophthalmitis with the use of an endoscope. Retina. 2005;25(8):976-80. 5. De Smet MD, Mura M. Minimally invasive surgery—endoscopic retinal detachment repair in patients with media opacities. Eye (Lond). 2008;22(5):662-5.

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183 6. Eguchi S, Araie M. A new ophthalmic electronic videoendoscope system for intraocular surgery. Arch Ophthalmol. 1990;108(12):1778-81. 7. Faude F, Wiedemann P. Vitreoretinal endoscope for the assessment of the peripheral retina and the ciliary body after large retinectomies in severe anterior PVR. Int Ophthalmol. 2004;25(1):53-6. 8. Fisher YL, Heringer GC. Endoscopy for vitreoretinal surgery. In: Peyman GA, Meffert SA, Conway MD, Chou F (Eds). Vitreoretinal Surgical Techniques. London: Martin Dunitz; 2001. pp. 107-12. 9. Hattori T, Sonoda KH, Kinoshita S. Two useful techniques of pars plana vitrectomy using endoscope. Eye (Lond). 2006;20(12):1466-8. 10. Kita M, Yoshimura N. Endoscope-assisted vitrectomy in the management of pseudophakic and aphakic retinal detachments with undetected retinal breaks. Retina. 2011;31(7):1347-51. 11. Leagis JM, Rol P, Briat B, et al. Rigid endoscope with gradient-index lenses. Preliminary studies. J Fr Ophtalmol. 1997;20(6): 439-43. 12. Leon CS, Leon JA. Endoscopie chirurgicale oculaire. Paris: Medsi/McGraw-Hill; 1990. 13. Norris JL. Vitreous surgery viewed through an endoscope. Dev Ophthalmol. 1981;2:15-6. 14. Norris JL, Cleasby GW. An endoscope for ophthalmology. Am J Ophthalmol. 1978;85(3):420-2. 15. Norris JL, Cleasby GW, Nakanishi AS, et al. Intraocular endoscopic surgery. Am J Ophthalmol. 1981;91(5):603-6. 16. Rol P, Beck D, Fankhauser F, Niederer P. GRIN-endoscopy for laser treatment in ophthalmology. Klin Monbl Augenheilkd. 1994;204(5):470-3. 17. Sabti KA, Raizada S, Kandari JA, et al. Applications of endoscopy in vitreoretinal surgery. Retina. 2008;28(1):159-66. 18. Sens FM, Prünte C, Kain HL. GRIN (gradient-index) intraocular endoscopy— possibilities and limits—a review. Klin Monbl Augenheilkd. 2001;218(5):316-22. 19. Sheindlin JA, Hirose T, Hartnett ME. Ophthalmic endoscopy: applications in intraocular surgery. Int Ophthalmol Clin. 1999;39(1):237-47. 20. Sonoda Y, Yamakiri K, Sonoda S, et al. Endoscopy-guided subretinal fluid drainage in vitrectomy for retinal detachment. Ophthalmologica. 2006;220(2):83-6. 21. Stewart MW. Management of retained lens fragments: can we improve? Am J Ophthalmol. 2007;144(3):445-6. 22. Uram M. Endoscopic Surgery in Ophthalmology. Philadelphia: Lippincott Williams & Wilkins; 2003. 23. Uram M. Laser endoscope in the management of proliferative vitreoretinopathy. Ophthalmology. 1994;101(8):1404-8. 24. Uram M. Ophthalmic laser microendoscope endophotocoagulation. Ophthalmology. 1992;99(12):1829-32. 25. Uram M. Ophthalmic laser microendoscope ciliary process ablation in the management of neovascular glaucoma. Ophthalmology. 1992;99(12):1823-8. 26. Volkov VV, Danilov AV, Vassin LN, et al. Flexible endoscope for intraocular surgery. Arch Ophthalmol. 1990;108(7):1037-8. 27. Volkov VV, Danilov AV, Vassin LN, et al. Flexible endoscopes. Ophthalmoendoscopic techniques and case reports. Arch Ophthalmol. 1990;108(7):956-7. 28. Sabti KA, Raizada S, Kandari JA, et al. Williams GA. Applications of endoscopy in vitreoretinal surgery. Retina. 2008;28 (1):159-66.

chapter 9

Minimal Incision Vitrectomy Surgery: Twenty-Three, Twenty-Five and Twenty-Seven Gauge José Juan Martínez-Toldos, Javier A Montero-Moreno, José M Ruiz-Moreno, Armadá Maresca Félix, Natalia Pastora-Salvador, Anna Grabowoska, María Granados-Fernandez, Beatriz Manzano Muñoz

9.1  TWENTY-THREE GAUGE VITRECTOMY José Juan Martínez-Toldos

INTRODUCTION The year 2002 saw the introduction of new smaller caliber instruments designed for conjunctival and scleral incisions of 0.6, 0.5 or 0.4 mm, which did not require sutures. In principle, the benefits of smaller caliber instruments include less damage to ocular tissues, diminished circulation of fluid in the ocular globe and because of the small surgical wounds created, more rapid recovery for the patient and a reduced amount of induced astigmatism.1,2 In 2004, Eckardt3 developed a 23-gauge system that is used in complex cases of proliferative diabetic retinopathy (PDR) or vitreoretinal proliferation. Given the similar strength of the instruments to those used in conventional 20 gauge surgery, there is no limit to the surgical procedures the new instruments can be used for; it is easier to control the position of the eye and to manipulate the instruments, as this often depends on the force they produce. The 23-gauge system also allows for suture-free incisions. Such incisions are achieved using a 23-gauge stiletto blade angled at 45° to create a valved incision through which metal trocars are introduced with the help of a pressure plate. Constant pressure is applied to the pressure plate while the incision is made and during withdrawal of the stiletto blade to prevent slippage of the conjunctiva against the sclera (Figs 1A to C). The illumination system provides sufficient light, and forceps, scissors, endolaser and endodiathermy probes, backflush aspiration systems have been developed in 23 gauge. The vitrector

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A

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Figures 1A to C  (A) Twenty-three gauge metal trocars with sealing plugs and infusion cannula; (B) The incision is made with the help of a pressure plate; (C) Inserting the stiletto blade with the trocar

has a cutting speed of 1,200 cuts per minute and aspiration power above 500 mm Hg. With small variations, this vitrectomy system has been widely developed and all the commercial firms offer a system of this caliber. Also, among surgeons, the system has become so popular that 72.5% of vitreoretinal surgeons routinely conduct 23-gauge vitrectomy.4 When starting on this type of surgery following 20-gauge vitrectomy, it is important to select cases that are not too complex until a certain comfort level has been attained in each step of the procedure. The treatment of vitreous hemorrhage and epiretinal membranes are good procedures to start with before moving on to cases of retinal detachment, macular hole and PDR. It should be stressed that instrument rigidity is similar to that of 20-gauge instruments and that it does not take long to adjust to the new technique. Fluid dynamics and control are good, especially with the new high-speed vitrectomy machines that offer working with duty cycles.

INCISION CONSTRUCTION Good wound construction is important to avoid cannulas becoming dislodged during surgery and ensure that the incision self seals so that there are no leaks that could provoke hypotension or increase the risk of endophthalmitis. In addition, we should seek to avoid the need for sutures. Today’s hollow trocars enable the incision to be placed and the trocar inserted in a single maneuver. Basically this consists of displacing the conjunctiva and then introducing the trocar and stiletto blade at an angle of 25–30° through the sclera in a slightly oblique direction to make a small tunnel, and then pointing toward the eye center to create an incision involving two planes, which will always be more airtight and safe. Valved cannulas exist which permit a tightly sealed surgical procedure with less turbulence within the eye. These cannulas are preferable to the more simple plugged cannulas. As in 20-gauge surgery, it is important to check that the infusion cannula is well positioned in the ocular cavity to avoid choroid detachment. We

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186 should start with the inferior temporal incision to position the infusion line and then introduce the instrument ports with a separation of 160–170° (Figs 2 and 3).

VITRECTOMY When working with a high-speed vitrectome, the duty cycle can be adjusted. We use the 50/50 cycle in the central vitreous and as we approach the retina, we switch to the shaving mode, which gives us the security that we will not damage the retina. Since the probes are longer and the cutting mouth is more toward the tip, we can get closer to the retina. In cases of PDR, the vitrector can be used as scissors by placing it under the membrane and cutting at high speed and low suction. This maneuver can be made easier if we use viscodissection to remove zones of traction without the need to introduce new instruments or the need for bimanual surgery.

Figure 2  New Edge Plus system by Alcon comprising a single-step trocar for a linear incision, metal 23- and 25- gauge cannulas with integrated silicone valves and vitrector with a 3.3–4 mm scleral marker

A

B

Figures 3A and B  Disposable 23G forceps ILM

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187 We can also use the vitrectome probe with active aspiration to lift membranes and detach the hyaloid. Using backflush we can displace blood and then by reducing the cutting speed eliminate pieces of tissue, clots or small crystalline lens fragments.

CLOSING THE INCISION To close the wound, we should lower the infusion pressure to around 20 mm Hg, to avoid losses through the cannulas. An instrument is attached to the cannula such as the illumination probe, the cannula is withdrawn retaining the probe and finally we can remove the probe and apply a gentle massage to the sclera so that the scleral fibers recover their memory. We can also use a 23-gauge needle to introduce a little air through the cannula before its removal to avoid or minimize losses and vitreous incarceration. If we have worked for a long time and the incision has been excessively manipulated, it is best to fill the globe completely with air. This will facilitate closing the incisions. Notwithstanding, if there is leakage and the eye shows a tendency toward hypotony, we should not hesitate to place a stitch using reabsorbable 8-0 sutures. If the incision is visible beneath the conjunctiva this can be done directly; if there is blood or we cannot see the incision well, it is best to place a linear cut in the conjunctiva to expose the wound and then close it well. The conjunctival incision does not require suturing. If silicone oil has been left in the eye, it is best to suture the incisions to avoid leakage. The main problems caused by a poorly closed wound are hypotony and endophthalmitis. An incision in a hypotonic eye has a siphon effect for the entry of microorganisms.

BENEFITS OF TWENTY-THREE GAUGE SURGERY Instruments are similar to those of 20 gauge in terms of rigidity and fluidics. Other than this, the advantages of twenty-three gauge surgery are: ƒƒ Incisions are usually airtight without sutures ƒƒ Less surgery time ƒƒ Since there are no sutures, there is usually no induced astigmatism ƒƒ It may be used in nearly all procedures except in very complex cases or foreign bodies although 20/23 gauge may be combined ƒƒ Faster recovery ƒƒ Reduced inflammation Owing to these benefits, 23-gauge vitrectomy is currently the preferred system and is used in over 90% of procedures.

COMPLICATIONS Several complications have been described for the use of 23-gauge vitrectomy: retinal detachment, cataract progression, persistent or recurrent vitreous

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188 hemorrhage, cystoid macular edema, conjunctival chemosis on the day following surgery, hypotony, endophthalmitis, intraoperative choroidal detachment and even hemorrhagic choroidal detachment.5 The appearance of endophthalmitis is directly related to incision closure and the practice of introducing gas in the eye has reduced the incidence of endophthalmitis from the initial 0.18% described in the literature to 0.04%, suggesting the possible benefit of fluid/air exchange at the end of surgery.6 Retracting the cannula during surgery has been proposed as an explanation for choroidal detachment as a complication. To avoid this problem, more pronounced 30–45° incisions are recommended so that the cannula can be introduced several millimeters in the vitreous chamber (a 15° incision would mean the cannula is scarcely introduced in the ocular cavity such that any slight retraction would make the cannula occupy the choroidal space and induce choroidal detachment). We should check that at least 2 mm of cannula have been introduced in the eye and then align the cannula at 90° to the sclera with the help of a Steri-strip.7

REFERENCES 1. Fujii GY, De Juan E, Humayun MS, et al. Initial experience using the transconjunctival sutureless vitrectomy system for vitreoretinal surgery. Ophthalmology. 2002;109(10):1814-20. 2. Fujii GY, De Juan E, Humayun MS, et al. A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology. 2002;109(10):1807-12. 3. Eckardt C. Transconjunctival sutureless 23-gauge vitrectomy. Retina. 2005;25(2):208-11. 4. American Society of Retina Specialist Annual Preferences and Trends Survey; 2010. 5. Lott MN, Manning MH, Singh J, et al. 23-gauge vitrectomy in 100 eyes: short-term visual outcomes and complications. Retina. 2008;28(9):1193-200. 6. Chiang A, Kaiser RS, Avery RL, et al. Endophthalmitis in microincision vitrectomy: outcomes of gas-filled eyes. Retina. 2011;31(8):1513-7. 7. Tarantola RM, Folk JC, Shah SS, et al. Intraoperative choroidal detachment during 23-gauge vitrectomy. Retina. 2011;31(5):893-901.

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9.2  TWENTY-FIVE GAUGE VITRECTOMY Javier A Montero-Moreno, José M Ruiz-Moreno

INTRODUCTION Since 1974, three-port, 20-gauge caliber surgery has been the gold standard for vitrectomy. However, during the past few years, interest has been mounting in the use of ever smaller caliber operating instruments to perform sutureless minimally invasive microincision surgery. Chen was the first to describe sutureless vitrectomy in 1996.1 In earlier work, Peyman had developed the 23-gauge caliber system, which was used mostly in pediatric surgery.2 According to a questionnaire about preferences and trends administered to the members of the American Society of Retina Specialists, 48% of those who completed the questionnaire in 2004 had never employed a small caliber system; in 2007, 75% admitted to using such a system at least once and in 2008, this figure was 80%.3 Among the benefits of sutureless transconjunctival vitrectomy we find, reduced surgical trauma, faster postoperative and visual recovery, and greater patient satisfaction.4-8 Moreover, transconjunctival access avoids the need to dissect and suture the conjunctiva and sclera, shortening surgery time thus increasing efficiency in the operating room, besides reducing surgical trauma, and the foreign body sensation produced by the increased manipulation that sutures entail and by possible reactions induced by the sutures themselves. The use of microcannulas facilitates the exchange of instruments from one entry port to another and protects the vitreous base from mechanical traction. Not least important, is the almost complete lack of scarring of the conjunctiva, which enables further operations if necessary. Among its drawbacks we could mention, suction and flow speed in the 25-gauge system are significantly lower than with 20 gauge as a consequence of the smaller caliber, which could make the removal of vitreous strands difficult. Further, 25-gauge instruments may seem more flexible. In effect, this was the reason for the initial restrictions of this gauge to cases not requiring extensive vitrectomy or to membrane dissections (such as epiretinal membranes, macular holes or vitreomacular traction syndromes). For these reasons, the popularity of transconjunctival sutureless vitrectomy with small caliber instruments has exponentially grown among ophthalmologists. However, parallel to its increased use have also grown the number of doubts about the airtightness of such self-healing incisions. Thus, a series of published reports has described a greater risk of postoperative hypotony and endophthalmitis compared to conventional vitrectomy.9-11 Over recent years, both the quality and variety of instruments for this type of surgery have increased and we today have available sets of instruments from the different companies (Dorc, Grieshaber, Millenium, Synergetics, among others) designed to undertake any vitreoretinal surgical procedure.

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190 Among these newly developed tools, we find single-step trocars that are easier to insert or two-step trocars that provide greater stability. Valved trocars exist that avoid the use of plugs, although they hinder the introduction of silicone-tipped cannulas. There is a large variety of light probes for each instance during surgery: stiff, flexible, with a pick, focal, intermediate or wide-field, as well as auxiliary light probes such as the Chandelier or Torpedo. There are also several types of laser probes: straight or curved, with or without illumination or the multidirectional retractile laser probe which is useful for endophotocoagulation in zones of difficult access. Similarly, we also have available a growing number of forceps and manual or pneumatically-driven scissors (Figs 1 and 2). Inserting the trocars is a key maneuver to prevent complications. Thus, the conjunctiva has to be sufficiently displaced such that the conjunctival incisions do not coincide with the sclerotomies (Fig. 3). Sclerotomies should be performed at an angle of 20–30° on the plane of the pars plana, parallel to the limbus. Their position should be at 2 o’clock and 5 o’clock for maneuvers and in the inferior temporal zone for infusion, all three at a distance of 3.5 mm from the limbus. To avoid suturing the lens retaining ring to the limbus, silicone rings (these require more assistant cooperation) or noncontact systems such as binocular indirect ophthalmomicroscope, Oculus or optical fiber free intravitreal surgery system, Topcon may be used. The vitrectomy itself does not vary from the 20-gauge technique, except that the smaller caliber infusion cannula determines a higher infusion pressure in the console (35–40 mm Hg) and a longer vitrectomy duration (Fig. 4). It is best to reduce the intraocular infusion pressure to 10–15 mm Hg as the operation is finalized and before removing the cannulas, to avoid the risk of excessive pressure forcing the incisions causing the passage of saline solution or gas to the subconjunctival space. The cannulas are removed one by one, in the same direction to their introduction while cutting the vitreous to avoid peripheral

Figure 1  Peeling an unstained epiretinal membrane using Eckardt pincers

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Figure 2  Stripping the internal limiting membrane after brilliant blue staining in a case of macular hole

Figure 3  Inserting the transconjunctival trocars

Figure 4  25-gauge vitrectomy

Step by Step Vitrectomy

192 vitreous hernias. Massaging the sclerotomies helps wound closure. This can be done using a microsponge to detect the presence of a vitreous wick.

BENEFITS OF MICROINCISION VITRECTOMY ƒƒ Surgery time is reduced since there is no need for conjunctival opening

ƒƒ

ƒƒ

ƒƒ

ƒƒ

or closing, or closing sclerotomies—between 10 minutes and 16 minutes depending on the series There is less postsurgery inflammation reducing the need for topical postoperative treatment and visual recovery is faster for the patient improving postsurgery comfort The ocular surface is better preserved along with limbus stem cells leading to reduced conjunctival scarring. In turn, this leads to the diminished appearance of postoperative ulcers or epithelial alterations, which is of special interest in diabetic patients and contact lens wearers A fourth port can be easily added so that the use of the ports and infusion can be easily exchanged reducing peripheral vitreous traction and the production of retinal tears. This benefit facilitates the introduction of lights such as the chandelier and torpedo, as additional support or for bimanual surgery As scleral sutures are avoided, this reduces the risk of corneal topographic changes and associated astigmatism.

DRAWBACKS OF MICROINCISION VITRECTOMY ƒƒ Maneuvering capacity is lessened due to the reduced rigidity of the

ƒƒ

ƒƒ

ƒƒ

ƒƒ

instrument ends. This makes it difficult to work in the retinal periphery and increases the risk of damaging the natural lens in phakic patients. The newer instruments have improved this feature of the 25-gauge system by providing more rigid ends Fluid dynamics is reduced compared to 20 gauge and 23 gauge, both for aspiration and infusion. Vitreous aspiration and cutting is slower for 25 gauge although in the new models, the cutter mouth is closer to the vitrector tip, which increases efficiency and enables more precise shaving of the peripheral vitreous A lower intensity of light is produced because of the caliber of the fiber. This shortcoming has been resolved in part by the more powerful xenon light source and lights with additional fibers (Chandelier) There is a risk of trocar dislodgement especially during prolonged surgery. This produces immediate intraoperative chemosis hindering surgery with a need to replace the trocar Instruments are more expensive than 20-gauge instruments although the trend is that they are becoming comparable in price

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193

COMPLICATIONS The most frequent complications of 25-gauge vitrectomy are related to sutureless sclerotomies.9-11 Postoperative hypotony is common but transient and is associated with a conjunctival chemosis that reabsorbs spontaneously but that may provoke ciliochoroidal detachments and macular folds. Postoperative vitreous hemorrhages can occur due to bleeding of the sclerotomies toward the vitreous cavity, especially in patients on anticoagulants. This complication seems to be related to the lack of diathermy in the sclerotomy zone and may be promoted by postoperative hypotony. Subconjunctival hemorrhages are frequent but insignificant. The most revealing study has reported a 0.018% incidence of endophthalmitis following 20-gauge surgery compared to 0.23% for sutureless 25-gauge surgery.9 Collectively, reported results suggest a cumulative incidence of 0.025% for 20 gauge versus 0.45% for 25-gauge.9,12,13 In a survey performed in 2007, 14.7% of responders admitted to having had at least one case of endophthalmitis following sutureless 25-gauge or 23-gauge surgery, so it seems evident that the rate of endophthalmitis is higher in these cases than for 20-gauge vitrectomy. This difference has been attributed by some authors to incision construction, since it seems that the risk of both postoperative infections, leakage and hypotony, and even of postoperative vitreous hemorrhage, was higher in the studies in which straight incisions were used compared to those placing angled incisions. Thus, it seems the wound architecture can be an essential factor. Similarly, it has been observed that the penetration, throughout the incision, of India ink applied to the conjunctiva, immediately after the intervention is greater in cases of straight incisions rather than angled incisions.14 Even when the sclerotomy has been initially well constructed, excessive manipulation and traction during surgery may induce changes in incision structure. In addition, other complications common to 20-gauge surgery, such as cataract, phototoxicity, etc. can be produced.

FUTURE PERSPECTIVES The considerable technical advances made in the field of microincisional surgery in recent years are likely to continue into the coming years. Areas in which there is still room for improvement include improving illumination, and resolving the issue of the excessive flexibility of instruments along with the efficiency of vitrectomes. Ideally these will permit up to 5,000 cuts per minute and adjustable cutting/aspiration cycles. This will also help shorten core vitrectomy times and improve the control of vitreous cutting in peripheral zones or close to a detached retina (Box 1). Apart from adequate incision construction, developments in sclerotomy closure techniques include the use of reabsorbable sutures and biological adhesives that help reduce losses, which occasionally occur despite making angled incisions.

Step by Step Vitrectomy

194 Box 1: Keys to microincisional surgery • Incision shape: angled sclerotomies (in two planes) are preferable to straight sclerotomies as the risk of an incision remaining half open is reduced and this is accompanied by a diminished risk of leakage and endophthalmitis • Instilling povidone iodine 5%: in the conjunctival fornices and over the bulbar conjunctiva to reduce the risk of microbes entering the vitreous cavity • Incision: –– Measure the distance to the limbus and displace the conjunctiva at the entry point –– Flatten the sclera to obtain the longest possible intrascleral path, which will allow for better apposition of the wound edges • At the end of the surgery: –– Undertake partial air/fluid exchange –– Withdraw the cannula with a solid instrument such as the light pipe to avoid vitreous wicks –– Massage the incision wound with a microsponge or cotton bud –– Wait for the wound to close –– Use a reabsorbable suture or adhesive if leakage persists –– Straight incisions need to be sutured.

These methods can be used in selected cases in which the surgeon has reason to suspect the incision may not be airtight.15

REFERENCES 1. Chen JC. Sutureless pars plana vitrectomy through self-sealing sclerotomies. Arch Ophthalmol. 1996;114(10):1273-5. 2. Peyman GA. A miniaturized vitrectomy system for vitreous and retinal biopsy. Can J Ophthalmol. 1990;25(6):285-6. 3. Mehran Taban, Peter K. Kaiser. (2009). Microincisional vitrectomy: techniques, tips and the future.[online] Available from www.retinaspecialistsorg/services/ pat_survey/. [Accessed March, 2008]. 4. Ibarra MS, Hermel M, Prenner JL, et al. Longer-term outcomes of transconjunctival sutureless 25-gauge vitrectomy. Am J Ophthalmol. 2005;139(5):831-6. 5. Lakhanpal RR, Humayun MS, de Juan E, et al. Outcomes of 140 consecutive cases of 25-gauge transconjunctival surgery for posterior segment disease. Ophthalmology. 2005;112(5):817-24. 6. Okamoto F, Okamoto C, Sakata N, et al. Changes in corneal topography after 25-gauge transconjunctival sutureless vitrectomy versus after 20-gauge standard vitrectomy. Ophthalmology. 2007;114(12):2138-41. 7. Rizzo S, Genovesi-Ebert F, Murri S, et al. 25-gauge, sutureless vitrectomy and standard 20-gauge pars plana vitrectomy in idiopathic epiretinal membrane surgery: a comparative pilot study. Graefes Arch Clin Exp Ophthalmol. 2006;244(4):472-9. 8. Yanyali A, Celik E, Horozoglu F, et al. 25-Gauge transconjunctival sutureless pars plana vitrectomy. Eur J Ophthalmol. 2006;16(1):141-7. 9. Kunimoto DY, Kaiser RS, Wills Eye Retina Service. Incidence of endophthalmitis

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195 after 20- and 25-gauge vitrectomy. Ophthalmology. 2007;114(12):2133-7. 10. Scott IU, Flynn HW, Acar N, et al. Incidence of endophthalmitis after 20-gauge vs 23-gauge vs 25-gauge pars plana vitrectomy. Graefes Arch Clin Exp Ophthalmol. 2011;249(3):377-80. 11. Scott IU, Flynn HW, Dev S, et al. Endophthalmitis after 25-gauge and 20-gauge pars plana vitrectomy: incidence and outcomes. Retina. 2008;28(1):138-42. 12. Aaberg TM, Flynn HW, Schiffman J, et al. Nosocomial acute-onset postoperative endophthalmitis survey. A 10-year review of incidence and outcomes. Ophthalmology. 1998;105(6):1004-10. 13. Eifrig CW, Flynn HW, Scott IU, et al. Acute-onset postoperative endophthalmitis: review of incidence and visual outcomes (1995-2001). Ophthalmic Surg Lasers. 2002;33(5):373-8. 14. Singh A, Chen JA, Stewart JM. Ocular surface fluid contamination of sutureless 25-gauge vitrectomy incisions. Retina. 2008;28(4):553-7. 15. www.retinalphysician.com/articleviewer.aspx?articleID=102833.

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9.3  TWENTY-SEVEN GAUGE VITRECTOMY Armadá Maresca Félix, Natalia Pastora-Salvador, Anna Grabowoska, María Granados-Fernandez, Beatriz Manzano Muñoz

INTRODUCTION Currently, 27-gauge instruments are being used to directly remove epiretinal membranes and for 27-gauge caliber vitrectomy.1,2 Thus, complete three-port vitrectomy with 27-gauge instruments are today being performed using the vitrectomes [Alcon Accurus (ALCON Fort Worth, Texas) and Dorc Associate (DORC 3214 VN Zuidland, The Netherlands)] with the Dorc vitrector probe (Fig. 1). Extracting epiretinal membranes directly without vitrectomy is a treatment mode designed to preserve the crystalline lens in patients susceptible to cataract because of their age.1,2 The use of ever smaller caliber instruments for vitrectomy or other surgical procedures seeks to improve recovery, induces less postoperative trauma, diminishes conjunctival scleral scarring, avoids suture-induced astigmatism and to achieve more rapid visual recovery and comfort for the patient.3,4 However, small-caliber surgical approaches are not free from several complications such as insufficient sclerotomy closure, the need for sutures in some cases and postoperative hypotony with the consequence of choroidal detachments. Although rare, the risks of bacterial contamination and postsurgical endophthalmitis need to be considered when performing a smallcaliber technique. Reducing the caliber of vitrectomy to 27 gauge may help diminish these complications, as induced risks are minimized.3,4

INSTRUMENTATION The instruments used so far for 27-gauge procedures are manufactured by Dorc and consist of a 27-gauge vitrector and valved, disposable metal 27-gauge microcannula mounted on a 27-gauge stiletto blade with a handle whose proximal end has scleral markings. The infusion line, also by Dorc, has a jawed tip to help connect it to the microcannula (Figs 1, 2, 3 and 4). The vitrectome with which these instruments are used is the Dorc Associate machine (DORC 3214 VN Zuidland, The Netherlands), but it is also possible to work with the Alcon Accurus (ALCON Fort Worth, Texas). As light pipes, a Dorc or Synergetics design can be employed with the Alcon Accurus, Dorc BrightStar or Synergetics Photon light sources (Figs 5 and 6). Twenty-seven gauge caliber laser probes are manufactured by Dorc and Synergetics, and with an adapter can be used with the Alcon laser system. The surgical instrument manufacturers Synergetics (Synergetics Inc., St Charles, MO, USA) and Asico (26 Plaza Drive Westmont, IL 60559, USA)

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197

Figure 1  Dorc’s 27-gauge vitrector

Figure 2  Cutting mouth of Dorc’s 27-gauge vitrector

Figure 3  Metallic valved trocar for 27-gauge vitrectomy

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198

Figure 4  Tip of Dorc’s 27-gauge infusion cannula

Figure 5  Self-puncturing 27-gauge light probe by Synergetics

Figure 6  Dorc’s 27-gauge light fiber

Chapter 9    Minimal Incision Vitrectomy Surgery: Twenty-Three ...

199 already offer in their catalogues a sufficient number of forceps, scissors, diathermy probes, spatulas and picks to conduct most current procedures, especially at the level of the macula. The firm Hurricane offers a 27-gauge cannula that is useful for aspiration of fluid/gas exchange maneuvers. Owing to a study by Oshima,5 we have available data to compare with the 25-gauge Total Plus system by Alcon. Thus, for the 25-gauge system versus the 27-gauge system, respectively: vitrector dimensions are inner diameter 0.347 mm versus 0.275 mm, outer diameter 0.515 mm versus 0.409 mm; distance from cutter mouth to its tip 0.33 mm versus 0.211 mm; cutter mouth area 0.066 mm2 versus 0.079 mm2; vitrector length 32 mm versus 25 mm; and vitrector tip displacement in response to a 0.5 N force (i.e. rigidity) 3.3 mm versus 5.8 mm.5 These data are provided in Table 1. The optimal duty cycle for the 27-gauge Dorc vitrectome is 1,000–1,500 cuts per minute and an aspiration capacity of 0.05–0.07 ml/second and power of 600 mm Hg.5 Optimal infusion pressures using a Dorc 27-gauge infusion system with an Alcon Accurus vitrectome are in our opinion 25–35 mm Hg. Using these pressures, maximum aspiration without cutting will not induce ocular prolapse due to the vacuum generated.

INDICATIONS The indications we propose for this caliber span from macular surgery in its entirety, with the exception of eyes with myopia magna, including macular hole, macular pucker, etc., to simple hemovitreous, vitreous opacities, vitreomacular traction, noncomplex proliferative diabetic retinopathy, vitreous biopsy, endophthalmitis and macular edema of different origins.6 Our first impression with the use of this equipment (with the Alcon Accurus vitrectome) has been the extraordinary cutting and suction capacity for this small caliber. The rigidity of the vitrector shaft enables working comfortably in the periphery and even entering the anterior chamber without the vitrector bending. Its shorter length than probes of higher caliber confer it this rigidity yet it is not

Table 1 Comparing the new 27-gauge instruments with the 25-gauge Total Plus system by Alcon 25 gauge

27 gauge

Inner diameter

0.347 mm

0.275 mm

Outer diameter

0.515 mm

0.409 mm

Cutter mouth-to-tip distance

0.33 mm

0.211 mm

Guillotine area (vitrector mouth area)

0.066 mm

0.079 mm

Length

32 mm

25 mm

Rigidity (displacement in response to a 0.5 N force)

3.3 mm

5.8 mm

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200

recommended for long eyes such as those with myopia magna. The 27-gauge infusion system generates the necessary intraocular pressure to undertake any type of maneuver such as achieving hyperpressure in cases of retinal bleeding or fluid/air exchange. For such exchanges, the Hurricane 27-gauge cannula needs to be used with the vitrectome’s active aspiration system.6 For illumination, the PHOTON I light source by Synergetics has proved sufficient for most vitrectomies. However, each light probe has its peculiar features. Thus, the 27-gauge Dorc system provides diffuse light, which is inadequate for macular surgery (comprising most vitrectomies for which it is used). The Synergetics probe is more useful for this purpose, since it gives more focal light. Nevertheless, both probes are excessively short and the macula is not properly reached by the light beam. This is perhaps the most significant drawback of the 27-gauge caliber system. In our experience, the forceps marketed by Asico are world apart from the remaining 27-gauge forceps available. Thus, their Corcostegui pick forceps are extremely good at grasping and their rigidity makes the surgeons forget that they are working with a caliber of 27-gauge. The remaining designs are a step behind these supplied by Asico.6 Both Synergetics and Dorc 27-gauge laser probes have proved their efficacy for photocoagulating even the peripheral retina. In our initial 10 surgeries using this caliber we have treated cases of epiretinal membranes, hemovitreous secondary to retinal central vein obstruction and to diabetic retinopathy, myopic foveoschisis, macular hole and combined cataract/ macular pucker. The mean surgery duration was 27.3 minutes. In no case was it necessary to suture the sclerotomies and mean intraocular pressure was slightly lower, 24 hours after surgery than the presurgery value—13.1 mm Hg compared to 15 mm Hg. At 1 week postsurgery, the mean was 16.1 mm Hg. Conversion to a larger caliber (23-gauge or 25-gauge) was not necessary in any case and there were no perioperative complications.

CONCLUSION In conclusion, we would say that the 27-gauge vitrector has a similar rigidity to the 25-gauge Alcon design, albeit shorter in length, and shows sufficient cutting and aspiration capacity. Optimal duty cycles are obtained from 1,000–1,500 cuts per minute for aspiration power ranges of up to 600 mm Hg. However, above a speed of 2,000 cuts per minute it is inefficient. Using a vented gas forced infusion pressure system, a range of 25–35 mm Hg is sufficient to maintain a flow rate of 0.05–0.07 ml/second, which is optimal for vitrectomy. The light pipe is clearly too short such that a focal light source is better than a more diffuse one. Our surgery times are slightly longer than those needed for 25-gauge procedures but this is because we are still at an early stage in the learning

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201 curve. As the caliber is reduced, so too are the risks of complications inherent to Micro-incision vitrectomy system, although there is still a need for new instruments and materials to improve the quality of surgery.

REFERENCES 1. Saito Y, Lewis JM, Park I, et al. Nonvitrectomizing vitreous surgery: a strategy to prevent postoperative nuclear sclerosis. Ophthalmology. 1999;106(8):1541-5. 2. Sawa M, Saito Y, Hayashi A, et al. Assessment of nuclear sclerosis after nonvitrectomizing vitreous surgery. Am J Ophthalmol. 2001;132(3):356-62. 3. Sawa M, Ohji M, Kusaka S, et al. Nonvitrectomizing vitreous surgery for epiretinal membrane long-term follow-up. Ophthalmology. 2005;112(8):1402-8. 4. Sakaguchi H, Oshima Y, Tano Y. 27-gauge transconjunctival nonvitrectomizing vitreous surgery for epiretinal membrane removal. Retina. 2007;27(8):1131-2. 5. Oshima Y, Wakabayashi T, Sato T, et al. A 27-gauge instrument system for transconjunctival sutureless microincision vitrectomy surgery. Ophthalmology. 2010;117(1):93-102. 6. Armadá Maresca, Félix, et al. Técnicas 27 gauge poderaoserutels? Libro: 25 Perguntas and Respostas Membranas Epirretinianas. GER Grupo de Estudios Da Retina: 2011. pp. 54-9.

chapter 10

Vitrectomy in Anterior Segment Surgery Complications José Juan Martínez-Toldos, Juan Carlos Elvira-Cruañes

INTRODUCTION Cataract surgery is one of the most frequently performed surgical procedures worldwide. Over the last few years, the technique has advanced tremendously especially since the use of phacoemulsification was proposed by Kelman.1,2 Today, there is no argument that the surgical treatment of choice for cataract is phacoemulsification, as a safe procedure offering rapid visual recovery. Phacoemulsification surgery has been completed with the use of topical anesthesia and sutureless corneal incisions. This type of surgery provides excellent results in the vast majority of cases. However, although infrequent, when complications do occur, these can lead to a significant loss in vision. It is, therefore, important that the surgeon knows how to manage these complications to minimize vision loss in these patients.

OCULAR PERFORATION IN RETROBULBAR ANESTHESIA As already pointed out, topical anesthesia is even more used by anterior pole surgeons, since it avoids the risk of perforation during retro-or peribulbar injection. Notwithstanding, in vitreoretinal surgery the use of retrobulbar anesthesia represents an advancement from the days when surgery was performed under general anesthesia. We have already mentioned that our anesthesia of choice is transconjunctival retrobulbar, which has provided excellent results. Although we generally use topical anesthesia, there are still cases in which the retrobulbar approach is preferred, such as in patients who do not cooperate, patients with neurological or psychic disorders; or in combined cataract/ glaucoma, cataract/vitrectomy surgery and when an intraocular lens (IOL) is fixed to the iris in aphakic patients with no capsule support.

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

203 Globe perforation while administering local anesthesia can be a rare yet serious complication occurring in 0.075–0.1% of the cases.3 Among the risk factors for this complication are axial myopia, posterior staphyloma and previous scleral surgery. The risk increases when axial myopia is associated with a small orbit impairing the control of the needle and following the needle as it crosses the tissue planes. It is also known that an eye size larger than 26 mm, staphyloma or the presence of a scleral buckle will also increase the risk of perforation. Duker et al4 estimated an incidence of 1 in 140 cases in these eyes. In such cases, the use of sub-Tenon’s peribulbar anesthesia may be considered, which consists of introducing anesthesia, avoiding its injection, via an incision in the anterior conjunctiva using a blunt metal needle into the sub-Tenon’s space. A variation of this is Fukasaku’s pinpoint anesthesia, whereby a long, curved, blunt-tipped cannula is inserted in the sub-Tenon’s space until close to the optic nerve.5,6 To avoid complications during the injection process, the “up and in” viewing position popularized by Atkinson should be avoided since in this position, the macula and optic nerve are more exposed and therefore more susceptible to damage. Mild sedation with propofol is thus recommended for anesthesia injection in the primary viewing position.

Transconjunctival Sub-Tenon’s Anesthesia The conjunctival incision is placed 10 mm from the limbus (usually in the inferior nasal quadrant, between the middle and inferior rectus muscles) until some 1.2 mm length of sclera can be observed. Next the sub-Tenon’s space is dissected and opened to help introduce the cannula, which should preferably be a blunt curved metal or plastic design of 20 gauge. The cannula is introduced and advanced through the sub-Tenon’s space until the retrobulbar zone is reached where a mixture of adequate anesthetic is injected (some 2–3 ml). A few minutes should be waited gently massaging the area to obtain the full effect. This form of anesthesia achieves good analgesia and akinesia. It is also a good rescue technique for incomplete/failed peri-or retrobulbar anesthesia or when surgery is complicated or prolonged in patients undergoing cataract extraction under topical anesthesia (in such cases it is best to suture the incision). Although some surgeons/anesthesiologists use a needle for sub-tenonian injection, a blunt cannula introduced through a conjunctival incision is safer in terms of avoiding ocular perforation and retrobulbar hemorrhage. The greatest shortcoming of this procedure is a higher incidence of conjunctival chemosis, which increases the risk of extrusion of current vitrectomy trocar systems. Chemosis may be drained by massage or even a conjunctival and Tenon incision to avoid this small problem.7

Ocular Perforation Ocular perforation may occur without previous warning. High intraocular pressure (IOP) can be induced when anesthetic is injected in the globe. Intraocular hypotension can also occur if the eye is perforated before the

Step by Step Vitrectomy

204 anesthetic is injected. Intraoperatively, a diminished or absent fundus reflex may be observed. After ocular perforation, vitreous hemorrhage or retinal detachments or tears are produced in most cases although these may not be detected until the first postoperative visit. Most intraocular anesthetics, especially lidocaine, are not toxic for the retina and vision is recovered in the patient after the accidental injection of anesthetic in about 16 hours. The most serious outcome of inadvertent anesthetic injection is central retinal artery obstruction due to the increased intraocular volume.8

Treatment Treatment requires that the problem is first identified. If suspected, cataract surgery should be delayed until the problem stabilizes and can be correctly identified. In cases of intraocular injection, the increased pressure can lead to occlusion of the central retinal artery. If this occurs, the patient will immediately go into amaurosis such that the elevated ocular tone can be felt, often accompanied by an immediate, progressive, intense corneal edema. In such cases, IOP should be reduced by an anterior chamber paracentesis and removal of the aqueous humor. We should also visualize using the indirect ophthalmoscope the state of the retina in peri/retrobulbar cases that show signs of: hemorrhage at the angle or anterior chamber, severe hypotony or hypertony or loss of previous fundus reflex in an early cataract. This could help the surgeon make the appropriate decision. Following anesthesia injection, if the ocular media is transparent and the retina is reattached and there is extramacular perforation, photocoagulation of the retina is performed at the site of needle entry. If vitreous hemorrhage exists, combined phacovitrectomy surgery is undertaken in which it is especially important to eliminate all the vitreous traction at the portal of entry by photocoagulating around the lesion. If there is a previous retinal detachment observed by ophthalmoscopy or ultrasound because of accompanying vitreous hemorrhage, we can also undertake phacovitrectomy. A scleral buckle is usually not necessary if vitreous traction has been adequately removed but should never be ruled out depending on the size of the tear or other factors indicating a poor prognosis. An auxiliary light can be used for this purpose, which will allow, with self-indentation, a more exhaustive peripheral vitrectomy. Linear tears can be seen at the needle entry point and these could subsequently detach the retina. Occasionally, retinal incarceration can occur, in which case we perform a phacovitrectomy with retinotomy to remove the traction caused by the incarceration and then undertake endophotocoagulation with posterior tamponade, usually with gas or air. When the macular area is affected by subretinal hemorrhage, phacovitrectomy can be carried out with retinotomy to remove the blood with the help of tissue plasminogen activator (tPA). If choroid hemorrhage is not too extensive, it could

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

205 resolve on its own. If not, 14 days later scleral drainage will help liquefy the blood and then surgery with transscleral drainage and intraocular injection of perfluorocarbon liquid can be performed.

RETROBULBAR HEMORRHAGE Retrobulbar hemorrhage occurs in approximately 0.3–0.44% cases of retrobulbar anesthesia.9,10 Predisposing factors for this complication are medication with anticoagulants, corticosteroids or nonsteroidal anti-inflammatory drugs. Systemic diseases such as thrombocytopenia and poorly controlled high blood pressure can also be risk factors, as can excessive handling of the needle during its insertion and the injection procedure. Several studies have revealed a significant flow reduction in posterior ocular vessels following a retrobulbar injection (even in the absence of hemorrhage).11 Retrobulbar hemorrhage causes rapid filling of the orbit with significant chemosis, proptosis and immobilization of the globe. The abrupt increase in IOP can compromise the intraocular vasculature.12,13 In most cases, compression of the globe with a finger can be enough to control bleeding. If the pressure is very high, we can perform a canthotomy to decompress the globe and avoid vascular effects. Surgery should be undertaken after a period of 15 days. If the lateral canthotomy fails to reduce the pressure on the ocular globe, an emergency orbitotomy can be performed. After opening the external canthal tendon and freeing its superior and inferior fibers, we access the retrobulbar space in the inferior temporal quadrant reaching the septum. The septum is dissected using blunt scissors and opened between the lateral and inferior recti. If there is hematoma associated with the high pressure, retrobulbar pressure may be reduced through this septal opening by means of the drainage described.14 There are three sites in the anterior orbit that are relatively avascular: (1) the inferotemporal quadrant (where the lateral third joins the medial two-thirds); (2) the superotemporal quadrant in the sagittal plane of the lateral limbus; and (3) the nasal component of the middle rectus. The superonasal quadrant should be avoided because of the presence of terminal vessels of the ophthalmic artery and the trochlea of the superior oblique muscle.15

ANTERIOR VITRECTOMY An anterior vitrectomy can be defined as the removal of vitreous from the anterior chamber, or the anterior third of the vitreous cavity. The approach can be anterior via the clear cornea, or sclerocorneal limbus, or posterior via the pars plana. Most common indications for an anterior vitrectomy are capsular rupture during cataract surgery or in cases of surgery for anterior segment trauma. Other

Step by Step Vitrectomy

206 indications are the removal of vitreal fibers bound to the iris or to the surgical wound, as a measure of avoiding complications related to vitreous adhesions such as cystoid macular edema or vitreocorneal touch syndrome, which could provoke corneal edema.

Vitrectomy Following Vitreous Loss The incidence of vitreous loss has been estimated at 0.8–1.25%16-19 and is most common in elderly patients with hard cataracts and with pseudoexfoliation syndrome owing to zonular weakness and poor dilation. Vitreous is lost when the posterior capsule is torn during surgery. The surgeon should be well aware of the signs that indicate capsular rupture such as deepening of the anterior chamber and difficult displacement of crystalline lens material. Often rupture occurs beneath the nucleus and passes undetected by the surgeon. When a posterior capsular rupture is detected, the surgeon should act quickly, yet calmly, first by withdrawing all instruments from the anterior chamber (Fig. 1) following the steps: ƒƒ Stop phaco tip aspiration ƒƒ Keep all instruments in the eye; do not remove them ƒƒ Maintain irrigation; pedal at position 1 ƒƒ Withdraw the paracentesis instrument ƒƒ Generously fill the anterior chamber with viscoelastic ƒƒ Once the anterior chamber has been filled with viscoelastic, the phaco tip can be removed and the situation assessed. Often the buttonhole widens as the pressure in the anterior chamber falls because of flow cessation without having adequately filled the anterior chamber with viscoelastic. Nevertheless, the chamber should be filled with viscoelastic for the remaining maneuvers. These maneuvers serve to keep the vitreous in place preventing its escape through the incisions. It is important to stop aspiration since the entire vitreous sac could be suctioned. The viscoelastic maintains the IOP and keeps the vitreous in a posterior position.

Figure 1  Capsular rupture. Aspiration through the phaco tip should be stopped and a constant intraocular pressure maintained, first with infusion fluid and then with viscoelastic

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

207 Traditionally vitrectomy was performed using the vitrectome with coaxial irrigation, which was inserted through the phaco incision lowering the height of the infusion bottle. However, this method has the consequence of enlarging the capsular tear and hydrating the vitreous, provoking its escape toward the anterior chamber and incisions. The use of the vitrectome with coaxial infusion is therefore not recommended (Figs 2A and B). We prefer to perform a vitrectomy using both hands;19 one for the irrigation cannula and the other for the vitrectome. If we place the vitrector at the phaco incision, infusion will cause the vitreous to escape through the incision and the vitreous fibers will become trapped in the postoperative course. To avoid this, we should: ƒƒ Make a new 1 mm incision close to the phaco incision making use of the pressure provided by the viscoelastic ƒƒ Introduce the irrigation tube through the paracentesis, lowering the infusion bottle height to 15 cm above the patient’s head; direct irrigation toward the iris and aspirate most of the saline with the vitrector to avoid hydrating the vitreous ƒƒ Introduce the vitrectome with no irrigation through the new incision (not the phaco incision) ƒƒ Place the vitrectomy probe just under the tear with the vitrector opening facing upward to extract the vitreous above the point of rupture ƒƒ The remains of the cortex can be removed by vitrectome aspiration. The normal irrigation/aspiration momentary cutting modes are useful to suction the cortex at the periphery (with no cutting function to avoid breaking capsule remains) and then cutting more in the center to minimize traction on small vitreous fibers that could be trapped. ƒƒ If the anterior capsule is intact, an IOL can be implanted by trapping its optics in the capsulorhexis; this creates a stable plane to complete the anterior chamber flushing procedure. These maneuvers are generally conducted with vitrectomy systems fitted

A

B

Figures 2A and B  (A) Anterior vitrectomy following capsular rupture; (B) The image shows the irrigation line and vitrector introduced through accessory incisions avoiding the main temporal incision

Step by Step Vitrectomy

208 to the normal phacoemulsifier. However, with the necessary experience and equipment, 23-gauge or even 25-gauge instruments (depending on the size and density or cortex remains) may be employed. A 23-gauge irrigation cannula may be adapted to the vitrectome infusion line and, through another corneal incision, the 23-gauge vitrector is introduced without the need for trocars.20,21 An infusion pressure of 20 mm Hg is set and we conduct a bimanual vitrectomy. Following a central vitrectomy in the pupil area, we proceed with the peripheral cortex. Depending on its density, the cutting speed can be dropped to 500–600 cuts per minute for its aspiration (Figs 3A and B). These maneuvers will enable us to pressurize the eye while controlling the vitreous. The pressure provided by the viscoelastic and the infusion cannula keeps the phaco incision closed. If not, the incision can be closed with a cross stitch.

A

B

Figures 3A and B  (Chalam et al) (A) After capsular rupture, the corneal wound can be sutured and 25 gauge trocars introduced for the anterior vitrectomy just beneath the capsule tear. The infusion cannula may be placed at the pars plana or the anterior chamber through the cornea; (B) Once the tear and anterior chamber have been freed of vitreous, the intraocular lens is placed in the sulcus with the help of viscoelastic

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

209 Vitrectomy can be undertaken without irrigation relying only on the viscoelastic pressure with the vitrectomy probe’s open side facing upward. As pressure is lost, more viscoelastic is introduced. This maneuver allows us to remove the vitreous that tends to escape without the need for irrigation. If a large amount of nucleus remains during anterior capsule rupture, the eye is pressurized using a dispersive viscoelastic placed under the nucleus (viscoelastic is also placed in the anterior chamber), displacing the vitreous. The irrigation bottle is then lowered, the nucleus is transferred to the anterior chamber and phacoemulsification undertaken in the anterior chamber, trying to avoid aspirating the vitreous. This is done by alternatively stopping to plug the phaco tip and continuing emulsification, then stopping to plug the tip again and emulsifying, etc. This process is repeated until the complete removal of the nucleus. We can then go on to perform a bimanual vitrectomy, as described above. A guide may be placed under the nucleus for the emulsification procedure with the help of viscoelastic as described by Michelson.22 If the nucleus is lost in the vitreous cavity, then the vitrectomy is performed as indicated; if the capsule exists, the IOL can be implanted and the patient referred to a posterior pole surgeon for standard vitreoretinal surgery. If the surgeon is an experienced anterior/posterior pole surgeon, then, in the same operation, vitreous surgery can be conducted and a sulcusor iris-fixated IOL is implanted. We prefer this last option.

RETAINED LENS FRAGMENTS The clinical situation that most frequently leads to the presence of crystalline lens or portions of the lens in the vitreous cavity, is capsular rupture during phacoemulsification (Figs 4A and B). This complication is more common in elderly patients with a hard nucleus and in cases of pseudoexfoliation. It is also more likely to occur in patients who have undergone previous vitreous surgery and also frequently occurs at the start of the learning curve for phacoemulsification. Its incidence is 0.3%.23 Sometimes, zonular weakness will lead to posterior dislocation of the lens without subsequent capsular rupture. Also posterior polar cataracts or traumatic cataract can induce the nucleus to fall. Several techniques have been described to treat a dislocated crystalline lens. These mostly include a three-port pars plana vitrectomy and the use of a perfluorocarbon liquid to refloat the crystalline lens to an anterior position.24-26 Other surgeons have described maneuvers performed during surgery that involve refloating the nucleus using large volumes of balanced saline solution (BSS)27 or applying the vitrectome with coaxial irrigation through the phaco incision and Machemer lens. 28 All these maneuvers and techniques are potentially dangerous, and have been linked to the possibility of giant retinal tears29 such that we do not recommend them. In these situations, the vitreous should be removed from the anterior chamber without excessive handling to avoid inflammation, and the IOL implanted. This is made possible because

Step by Step Vitrectomy

210 of the presence of capsular remnants or an intact anterior capsulorhexis; the luxated crystalline lens can then be approached. If the crystalline lens is very hard, it is best not to implant a lens in case it has to be removed anteriorly (Box 1). The most common clinical manifestation of a dislocated crystalline lens is diminished vision in the postoperative course. Poor visual acuity is a consequence of intraocular inflammation, which is directly related to the amount of crystalline remains and the extent of surgical manipulation. This inflammation increases during the 1st week and may then start to decrease. In a high proportion of cases, IOP increases. This is due to obstruction of the trabeculum by inflammatory cells or lens particles. Corneal edema is another constant sign of this problem and is related to surgical manipulation, mass remains in the anterior chamber and a high IOP. The occurrence of vitreous hemorrhage in the postoperative course is related to inadequate pressure changes or trauma to tissue due to posterior dislocation of the lens or part of the lens. Retinal detachment is not a consequence of the presence of crystalline material in the eye rather it is produced by the manipulation needed during cataract surgery or posterior vitreous surgery to extract the lens. Hence, traction of the vitreous gel will subsequently provoke retinal tears and detachment. The appearance of this problem markedly worsens the visual prognosis.

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Figures 4A and B  (A) Soft nucleus located in the anterior vitreous; (B) An almost complete nucleus in the posterior vitreous. Note the initial cuts made for the “divide and conquer” maneuver Box 1: Managing a dislocated crystalline lens • • • • •

Avoid panicking; do not undertake any unplanned maneuvers Perform an anterior vitrectomy without leaving vitreous in the wound If there are capsular remnants implant an intraocular lens If the cataract is very hard avoid intraocular lens placement Apply ocular anti-inflammatory and hypotensive agents.

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Surgical Indications It is clear that large fragments of crystalline lens will not be well tolerated by the eye and that vitreous surgery should be pursued as soon as possible after the corneal edema resolves, which is the limiting factor for surgery. When crystalline remnants are small and soft, that is, when fewer than 25% are less than 2 mm in size,30 the patient should be monitored. However, we should always be prepared, since if the inflammation does not resolve, we will have to undergo surgery because lens remnants could exist in the anterior vitreous or beneath the iris that could go undetected. In our experience, any hard crystalline lens fragment should be removed. If we wait too long, we run the risk of substantial inflammation with vascular effects such that we prefer to pursue surgery in these cases. Soft lens remains are simply monitored, and vitreous surgery undertaken if we are unable to control the inflammation. Sometimes a patient may have soft lens remnants in the bag, which become displaced in the postoperative course to the papillary area inducing a pseudocataract. In these cases, we also pursue early surgery. The time from dislocation to surgery should always be as short as possible and never exceed a month (Box 2).

Associating Surgery at the Time of Lens Dislocation If the surgeon performing cataract surgery is also (as often occurs) a vitreoretinal specialist, conversion to standard vitreous surgery may be conducted at the time of lens dislocation. Each day there are more machines available with Venturi and peristaltic pumps so that phacoemulsification and vitrectomy can be performed with the same equipment. In effect, we conduct vitreous surgery at the time of lens dislocation. The corneal incision should be sutured before proceeding with the vitrectomy. The advantages of performing vitreous surgery at the time of lens dislocation are: ƒƒ No complex maneuvers are needed ƒƒ The eye is not excessively manipulated ƒƒ The cornea is kept free from edema ƒƒ No inflammation has been produced at this stage ƒƒ An IOL can be placed on capsule remnants Box 2: Surgical indications for a dislocated crystalline lens • • • • • •

Large lens fragments Hard lens fragments, irrespective of size High intraocular pressure Noncontrollable uveitis Pseudocataract due to cortical remains Early surgery: 10–15 days, maximum 30 days

Step by Step Vitrectomy

212 ƒƒ If we lack capsular support, an Artisan lens can be fixed to the iris in the

anterior chamber or behind the iris. The drawbacks of immediate vitrectomy are usually associated problems: a greater risk of choroidal hemorrhage due to prior manipulation of the anterior pole and the presence of an adhered posterior hyaloid. This will need to be lifted to adequately remove the crystalline lens fragments and avoid postoperative complications such as retinal detachment and macular pucker or macular edema. Thus, in a single surgery, the problem can be resolved avoiding the need for a second operation allowing for faster recovery of vision. Moreover, surgery is ambulatory so the patient can go home.31 For conversion to vitreous surgery, we first have to close the corneal incision with a cross stitch, pressurizing the eye with viscoelastic, and then administer anesthesia, preferably sub-Tenon’s peribulbar, as described at the beginning of this chapter.

Surgical Technique Our current preference is the use of 23-gauge transconjunctival trocar systems. After introducing the trocar for the infusion line a superior trocar is introduced. A conjunctival incision is made and the sclerotomy widened to 20-gauge if the phacofragmentor will need to be used and we lack a 23-gauge phacofragmentor or phacoemulsifier. Infusion via 23-gauge avoids hypotony (even with the 20-gauge phacofragmentor) if we set a pressure of 30 mm Hg or more, especially if we can control intraocular pressure as with the latest vitrectomy machines. However, 25-gauge systems could be dangerous due to imbalance between infusion and aspiration. With the 23-gauge trocars we try to eliminate as much of the vitreous possible, producing posterior detachment of the hyaloid, along with all the crystalline lens fragments possible. The phacofragmentor needs only be used for the harder fragments that cannot be eliminated with the vitrectome even at high aspiration power and low cutting speed (300–400 cuts per minute). It is very useful to have an auxiliary torpedo or chandelier-type light source. First, we perform a central and peripheral vitrectomy as exhaustively as possible to avoid aspirating further vitreous in the aspiration or emulsification maneuvers with the retinal traction this would produce. It is known that vitreous cannot be emulsified. We should especially insist on the sclerotomy through which we will later introduce the phacofragmentor, since due to its larger mouth and aspiration without cutting it is easier to inflict retinal damage. The hardness of the crystalline lens is graded 1–4 (1-soft, 2-semisoft, 3-semihard and 4-hard). The following situations can be encountered: ƒƒ Soft remnants (grade 1) at the anterior and posterior poles ƒƒ Medium hardness remains (grade 2–3) at the posterior pole ƒƒ Hard crystalline lens remains (grade 4) ƒƒ Remains of any grade with retinal detachment ƒƒ Hard lens remnants with retinal detachment

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213 When lens fragments are soft, they can be easily removed with the vitrector both from the anterior and posterior pole. The anterior pole is cleaned by freeing the vitreous and conducting an anterior vitrectomy with indentation to remove vitreous as much as possible. We then continue by aspirating the cortical remnants that remain in the capsular bag with the vitrector, always trying to preserve sufficient remnants for IOL placement or to avoid the displacement of an already implanted IOL (Figs 5A and B). The momentary mode of vitrectomy is very useful to remove these cortical remains. First, we suction cortical masses in the periphery (to avoid breaking capsule remains) and then switch to cutting mode in the center. We then check whether the hyaloid is attached and remove it with aspiration to the periphery. Surgery is completed by conscientiously revising the retinal periphery to check for tears or holes. Any small retinal breaks are treated with laser or cryotherapy, and fluid/air exchange is undertaken as a preventive measure. In the case of a harder crystalline lens (grade 2–3), we will have to use the phacofragmentor. The first step is to free the crystalline lens from the vitreous with the vitrector, ensuring it falls to the posterior pole. We should then continue to eliminate all possible remains with the vitrector, which is always safer than the phacofragmentor. Once the crystalline lens has fallen to the posterior pole, the state of the posterior hyaloid can be verified. If it cannot be observed, the use of triamcinolone will help. A sign that the hyaloid membrane is attached is that the fragments do not freely move and often they spring back toward the retina as the hyaloid also incarcerates at the mouth of our probe. Once the hyaloid has been eliminated, we can introduce a little perfluorocarbon to protect the retinal posterior pole. If we introduce too much, because of the convex surface of the perfluorocarbon bubble, the lens will move to the periphery impairing its visualization and approach.

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Figures 5A and B  (A) Soft crystalline lens remnants that fully occlude the pupil impeding visualization of the fundus; (B) These cortical remnants are removed under aspiration using the vitrectome with no cutting function

Step by Step Vitrectomy

214 In most cases it is sufficient to partially refloat the crystalline lens to roughly the distal third of the vitreous cavity. For very hard lenses, it is recommended they should be refloated to a plane behind the iris before their phacofragmentation. With the phaco tip we approach the crystalline lens fragment and aspirate to trap it and lift it to the center of the eye where, with the help of the endoillumination probe, we continue with its emulsification. Usually the lens will break up into pieces that fall to the posterior pole and these need to be repeatedly retrieved and lifted until only small fragments remain. At this point, we again use the vitrectome to eliminate them and to aspirate any cortical remains that may persist. The phacofragmentor settings should be pulsed (maximum number of pulses possible) linear-mode ultrasound and medium vacuum (80 mm Hg, always with the crystalline lens at the phaco tip). Special attention has to be paid at the times the point becomes exposed because this is when most aspiration is exerted on the vitreous cavity, such that we need to lower aspiration at these moments. To keep the crystalline lens stuck to the phacofragmentor tip, we should use low ultrasound power. This will avoid the lens fragments shooting out from the phaco tip (Figs 6 A and B). The anterior pole phacoemulsifier may also be used, though with the drawback of its shorter tip (yet sufficient in most cases). If we use the Ozil system, fragments are more easily retained on the phaco tip and thus more easily eliminated. Surgery is completed by revising the periphery. If the crystalline lens is hard (grade 3–4), it will be difficult to remove and many aspiration/lifting maneuvers will be needed (Fig. 7). Ultrasound power may be increased and it is recommended that the lens be luxated to a retroiridal plane. The anterior pole phacoemulsifier may also be used, which we introduce with a microtip without irrigation through the sclerotomy. The drawback is that it is shorter than the phaco tip and it is more difficult to reach the posterior pole. As a benefit, however, it is extremely efficient and much quicker. Low powers are used to avoid repelling the lens fragments

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Figures 6A and B  (A) Freeing the posterior hyaloid with triamcinolone and the vitrectome active; (B) Phacofragmentation of the nucleus with the aid of the endoillumination probe

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215 and a little perfluorocarbon is introduced over the macular area to protect it from the fallout of lens fragments. We have been using the phacoemulsifier for more than 10 years and have never had any problems of burns at the corneal incision. This instrument is tremendously efficient if it is used with low flow rates (10–15 ml/minute) and low ultrasound power in pulsed mode to keep the crystalline lens fragments stuck to the tip. A type of smoke is produced upon emulsification that fills the vitreous cavity, and this has to be aspirated to restore good visualization (Figs 8A and B). It is also best to previously protect the corneal endothelium with viscoelastic.

Figure 7  In the case of hard remnants, we can use viscoelastic alongside perfluorocarbon to keep the crystalline lens fragments in the central zone and avoid their displacement to the periphery promoted by the convex surface of the perfluorocarbon bubble. If the perfluorocarbon bubble is small, viscoelastic is not needed

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Figures 8A and B  (A) As we emulsify the nucleus in the vitreous cavity, smoke is produced at the start of the maneuver; (B) Lifting the nucleus to the middle portion of the vitreous to start emulsification. The tip of the phaco has been plugged but aspiration is maintained providing good retaining power

Step by Step Vitrectomy

216 During phacofragmentation or phacoemulsification, small drops of saline can splash both wide-field contact lenses or noncontact visualization systems, which will consequently need to be cleaned. The small particles remaining on the retina can be removed with the vitrectome and we can get closer to the retina with sufficient safety. If the patient presents retinal detachment besides a dislocated natural lens, we first emplace a scleral buckle and then revise the anterior chamber since there are often remnants of masses that hide in the anterior angle. Special attention should be paid to eliminating vitreous remains on any retinal tears; we might find to avoid the introduction of perfluorooctane as the lens is refloated and the entry of subretinal fragments. We then perform anterior and posterior vitrectomy and introduce the perfluorocarbon liquid to reattach the retina and refloat the fragments to an anterior position, where with the vitrector they can be removed if soft. If harder, we can use the phacoemulsifier or fragmentor, setting the parameters mentioned above. In this case, if we place the probe in the pupillary area close to the level of the iris, we can use a spatula to keep the fragments on the tip; we use the microscope light as if we were undertaking anterior pole surgery without the need for endoillumination at this stage. Following emulsification, we apply the endolaser, implant an IOL if not already placed on capsular remnants, or even better, trapped in the anterior capsulorhexis if intact. If there is no capsular support, we can fix the IOL to the iris, having previously revised the periphery. This surgery procedure is completed with perfluorocarbon/air and air/gas exchange, maintaining the habitual tamponade proportional to the case. In the uncommon event of a retinal detachment and a dislocated very hard crystalline lens, the procedure is as follows: ƒƒ Placement of a scleral buckle ƒƒ Anterior and posterior vitrectomy ƒƒ Perfluorocarbon to reattach the retina and refloat the nucleus to the most anterior plane possible ƒƒ Phacoemulsification with the help of a Sinskey hook and light from the microscope ƒƒ If we think that too many maneuvers will be needed, the lens fragment may be displaced to the anterior chamber and then removed via a corneal incision ƒƒ Revision of periphery with indentation ƒƒ Endolaser therapy for tears ƒƒ Implant of an iris-fixated IOL in the anterior chamber or behind the iris ƒƒ Perfluorocarbon/air/gas or if necessary silicone oil exchange. In the latter case, an additional inferior iridectomy would be needed.

INTRAOCULAR LENS DISLOCATION The decentration of a posterior chamber IOL occurs in 0.2–1.2% of the cases and does not usually require treatment.32,33 Less common but more complicated

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217 is an IOL luxated to the vitreous chamber. A feature shared by all cases is a lack of sufficient capsular support (Figs 9A and B). The general course of events is capsular rupture, IOL placement and a few days or weeks later, its subluxation or complete dislocation. Other causes are dislocation following anterior segment trauma, or spontaneous dislocation including the capsular bag due to a zonular defect34 as in pseudoexfoliation syndrome. Other described cases have been dislocations in patients of an advanced age with high myopia, previous vitrectomy and some connective tissue disorders.35 Also certain silicone plate lenses can be dislocated as the result of capsule contraction following YAG laser treatment.36 Recently, the dislocation of a silicone lens implanted in the posterior chamber above the crystalline lens (phakic refractive lens) has been described. This type of lens is implanted in patients with high myopia who suffer dislocation to the vitreous chamber due to probable zonular damage and who, being phakic, require a vitrectomy with lens removal via the pars plana37 (Fig. 10).

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Figures 9A and B  (A) Complete dislocation of a polymethylmethacrylate lens with an intact capsular bag in a patient with high myopia; (B) Dislocated lens in a patient undergoing cataract surgery 2 years previously

Figure 10  Dislocated posterior chamber phakic refractive lens with risk of passage to the vitreous chamber

Step by Step Vitrectomy

218 A dislocated lens may be explanted and replaced or repositioned. Repositioning the lens in the sulcus by means of today’s vitreoretinal surgery seems a good option to achieve good vision. Thus, many techniques have been described to resolve this problem, which may be managed in a variety of ways: ƒƒ Repositioning the lens via an internal approach: –– The most simple option is to reposition the lens on the anterior or posterior capsular remnants without the need for suturing. However, the lens could again become displaced in which case its removal or placement in the sulcus would be recommended –– After removing the posterior chamber lens, it may be implanted in the anterior chamber.37,38 This option is sometimes used in elderly patients since it barely requires manipulation, although the patient has to have a good endothelial cell count since 30% endothelial loss is produced.39 Accordingly, we do not recommend this technique –– We can also fix the lens to the iris. This involves placing the lens in the anterior chamber and luxating its haptics behind the iris. When in position, the haptics are sutured to the iris and the lens optics can be introduced into the posterior chamber.40-42 This position of the lens is more physiological although it will have to be established whether it induces pigment dispersion with the risk of secondary glaucoma –– The lens can be repositioned in the sulcus with scleral fixing sutures. To do this, we can refloat the IOL with perfluorocarbon liquid and transiently externalize the haptics to place the suture.43-48 This method has been widely used and its related problems are well known and include: external erosion of the suture, endophthalmitis, decentration, tilt, dislocation, vitreous and choroidal hemorrhage, and cystoid macular edema. –– In 2007 a new suture-free scleral fixation technique via a scleral tunnel was introduced.49,50 ƒƒ Repositioning the lens via an external approach: –– In this way we can remove the IOL, place the sutures and implant it in the sulcus fixing it with the suture. In this case, we can use the same lens that has become dislocated, or implant a type of lens designed for this purpose with holes for sutures.51-55 The implant of the lens through a small self-sealing corneal incision has also been described –– The IOL may be fixed to the sclera without sutures through a scleral tunnel –– Another possibility is to remove the IOL and if there is no capsular support implant a new IOL in the anterior chamber fixed to the iris. The lens designed for this purpose is the Artisan “iris-claw” lens, which has iris-fixating haptics. Currently, Eckardt implants this type of lens behind the iris after hooking the haptics on the posterior iris surface.56,57

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Surgical Technique In all cases, we perform an anterior and posterior vitrectomy and check if the hyaloid is detached or attached to the retina. The IOL is usually stuck in the vitreous in the inferior globe, so we should undertake vitrectomy to free the lens and deposit it at the posterior pole. The lens should not be first manipulated since this could traction the vitreous causing retinal tears, which could provoke its detachment and compromise the visual outcome. Once the vitrectomy is finished and the lens freed, we can proceed to lift the lens using the following maneuvers:

Use of Perfluorocarbon Liquid To refloat the lens, we have to place the perfluorocarbon bubble under the IOL and as the bubble enlarges, the lens is displaced to an anterior position. To avoid the perfluorocarbon bubble settling on the lens and squashing it against the retina, it should be lifted and positioned vertically with the help of forceps or the light pipe and injection system. Once the lens has been grasped, we can fill the eye with perfluorocarbon until the lens adopts an anterior position behind the mydriatic pupil (Fig 11).

Lifting the Lens with Forceps When we lift the IOL using forceps by the anterior haptic, as we reach a superior position we will need another instrument such as a spatula to retain the lens and place it in the anterior chamber. This maneuver is therefore bimanual. According to Ducorneau, we can lift the lens in a single maneuver. To do this, we grasp the posterior haptic, lift the lens, turn the forceps 180° and lift until the anterior haptic reaches the anterior chamber angle. Next, the posterior haptic held with the forceps can be placed in the lower half of the angle. For this maneuver,

Figure 11  Refloating a lens with perfluorocarbon: the lens is grasped using a light probe with pick and a Chang cannula until it reaches an anterior position

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220

Figure 12  Refloating using the vitrector

the haptics have to be able to keep the entire lens in an upright vertical position. With polypropylene haptics this is difficult, although these have practically disappeared from the market. As we enter the anterior chamber, the wide-field visualization system should be withdrawn and we can then switch to direct viewing through the microscope. It is also possible to refloat the lens inserted in the bag and dislocated, using the suction handpiece vitreotome (Fig. 12) Once the lens is in position we can perform the following maneuvers: ƒƒ Implant the lens in the sulcus if there is sufficient anterior and posterior capsular support. If the anterior capsulorhexis is intact, we pass the IOL through it to implant it in the sulcus trapping its optics in the capsulorhexis; this provides a stable fixation plane with little risk of decentration. If an IOL reimplanted in the sulcus is again dislocated by rotation or the contraction of capsular remains, it is best to remove the lens and undertake another form of implant ƒƒ The posterior chamber IOL can be reimplanted in the anterior chamber. This could be a good option for elderly patients or patients with a high endothelial cell count. However, we do not recommend this strategy due to the high endothelial loss induced ƒƒ Implant the lens in the posterior chamber sutured to the iris. The lens is first placed in the anterior chamber with the haptics displaced to the posterior. In this position, the haptics are sutured to the iris and the entire lens finishes up behind the iris. The risk of pigment dispersion inducing glaucoma will later have to be checked ƒƒ Suturing the lens to the sulcus. For this we prefer to externalize the haptics to place the suture and thus avoid dangerous intraocular maneuvers ƒƒ Implant the aphakic Artisan lens in the anterior chamber, anchoring the haptics on the anterior iris surface or as described by Eckardt jabbing the haptics behind the iris, leaving the lens in the posterior chamber ƒƒ Our technique of choice is an aphakic Artisan lens implanted in the anterior chamber although recently we have been placing this lens in the posterior chamber.

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Implanting an Aphakic Artisan Lens This is the lens of choice when there is no capsule support. We have been implanting the Artisan lens in aphakic patients for several years. Its use provides good chamber depth, allows for good visualization of the retina, and if required, vitreoretinal surgery can be performed.56,57 Surgery is performed in a single procedure in cases of traumatic dislocation, crystalline fragments persisting after cataract extraction, complete dislocation of the lens and capsular bag and dislocation due to insufficient capsular support. Undertaking surgery after vitrectomy has the drawback that we lack vitreous support and the globe has a tendency to collapse as we try to work in the anterior chamber. ƒƒ This problem can be resolved by: Working with an open infusion line: this will give us ocular tone but will induce protrusion of the iris as we manipulate the anterior chamber with the risk of bleeding and rupture of the iris ƒƒ Filling the globe with perfluorocarbon: sufficient tone for lens implant can be achieved by introducing viscoelastic in the anterior chamber, but after this we should undertake perfluorocarbon/fluid exchange with the pupil closed. Surgery can be done using a wide-field visualization system since not much mydriasis is needed ƒƒ Positioning a Flieringa ring to avoid the globe collapsing: sutured to the sclera, this ring provides sufficient stability in the anterior chamber, which will have to be filled with viscoelastic (Figs 13A to C). To implant the IOL in the anterior chamber, a 5 mm corneal incision is made and acetylcholine is introduced to close the pupil, and viscoelastic, to give tone and protect the endothelium. The lens is slightly curved and should be placed concave downward on the iris. Then with the help of forceps and a hook, the lens is fixed to the iris (Figs 14A and B). If we wish to implant the IOL behind the iris, we can also apply acetylcholine and viscoelastic and introduce the lens concave upward so that the haptics hook onto the iris and there is no tent effect. The lens is introduced into the anterior

A

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C

Figures 13A to C  (A) Anchoring the Artisan “iris-claw” lens in the anterior chamber. Note the Flieringa ring and lens placed concave side downward; (B) Fixation is achieved with the help of retaining forceps and an anchoring hook; (C) Fixation maneuver on the opposite side using the same instruments

Step by Step Vitrectomy

222

B

A

Figures 14A and B  (A) Lens with slight curvature. The concave side faces upward as the lens is placed behind the iris to avoid tenting; (B) With the concave side facing downward, the lens is positioned on the iris in the anterior chamber

chamber, the lens optics is grasped with T-forceps in the center of its diameter and the lens is displaced through the pupil. In this position, the haptics are marked behind the iris to create an imprint on the iris so that, with the help of a spatula, the lens can be anchored to the posterior side of the iris (Figs 14, 15 and 16).

Late Intraocular Lens Dislocation with the Capsular Bag The standard of care for cataract surgery is phacoemulsification with the implant of an IOL in the capsular bag. However, an optimal surgical result does not guarantee a postoperative course without complications. Anterior and posterior capsular opacification, capsular contraction and closure, and cystoid macular edema are some of the well-known complications of the state-of-theart cataract surgery. Following cataract surgery, the complication of IOL decentering or dislocation to the posterior chamber occurs at a reported incidence between 0.2% and 3%. The causes are loss of zonular or capsular integrity during surgery or the asymmetric placement of the lens haptics.

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Figures 15A and B  (A) Lens newly implanted behind the iris; (B) Appearance of the lens on the day after surgery in another patient

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C

Figures 16A to C  (A) Implanting the lens behind the iris: the lens is grasped with T-shaped forceps by the middle portion of the optics; (B) Lens positioned behind the iris. An imprint is made behind the iris and using a spatula the haptics are fixated; (C) Fixation is repeated on the opposite side

Dislocation of an IOL with the capsular bag is a late complication described with increasing frequency as a result of progressive zonular dehiscence. Its real incidence is unknown but 20% of the surgeons admit they have encountered this complication and cases have been described to arise from 4.5 months to 16 years. The incidence reported in 2009 in a 10-year study including 810 cataracts was 1%.58

Mechanisms Predisposing conditions are pseudoexfoliation in 50% of the cases followed by other circumstances such as uveitis, trauma, vitrectomy and a long axial length.59,60 Associated factors are preoperative zonular weakness, surgical trauma to the zonules, capsular contraction syndrome and postoperative trauma. Zonular weakness has been well described in pseudoexfoliation syndrome, high myopia, as an outcome of vitreoretinal surgery and in some connective tissue disorders (Marfan syndrome, homocystinuria, hyperlysinemia, scleroderma, Ehlers-Danlos syndrome and WeillMarchesani syndrome).

Prevention Small continuous curvilinear capsulorhexis increases fibrosis and contraction, thus if these signs are detected the use of the YAG laser to create relaxing cuts is recommended. During phaco, efforts should be made to preserve zonular integrity with chopping techniques being the safest. Tangentially aspirating the cortex more or less perpendicular to the zonule may minimize zonular dehiscence. The use of a capsular tension ring is indicated in cases of pseudoexfoliation, although this may reduce but not prevent capsule contraction. In eyes with significant zonular weakness, the use of tension rings could diminish the incidence of luxation by increasing resistance to capsular contraction.

Step by Step Vitrectomy

224 In cases of advanced pseudoexfoliation, lens placement at the sulcus with its optics captured in the capsulorhexis has been described to avoid displacement though this induces inflammation. In eyes undergoing vitrectomy, sparing of the anterior hyaloid membrane has been proposed.

Treatment Some cases of a subluxated IOL may be followed by observation only. However, a loss of visual acuity, monocular diplopia or halos are indications for surgery. Oshika described a simple technique in which the subluxated bag was fixed using a double-armed 9-0 polypropylene (Prolene) suture to the sulcus through a clear cornea stab incision (Fig. 17).61 One needle goes over the haptic and capsular bag under the iris and out through the ciliary sulcus; the other needle penetrates the capsular bag under the haptic and exits through the ciliary sulcus. Alternatively, the subluxated IOL containing bag can be sutured to the iris with the help of a second instrument using 10-0 Prolene suture (Figs 18A and B). The IOL should be stabilized and there should be good ocular tone to

Figure 17  Sulcus fixation of an intraocular lens in the bag using a double-armed suture

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Figures 18A and B  (A) Stabilizing an intraocular lens using a straight 10-0 suture needle; (B) Fixating the fibrous capsule to the sulcus

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

225 manipulate the sutures well. We use 23–25 gauge vitrectomy instruments for this technique. An ingenious technique uses viscoelastic introduced through the pars plana to lift and retain the lens in the center, and then a spatula is introduced through the pars plana to help pass the suture to the iris and the bag-IOL complex. Also described, has been the use of a straight needle passed through the ring of capsular fibrosis with the help of anterior chamber infusion. In cases of complete dislocation requiring IOL explant, a good option is an Artisan lens fixated to the anterior iris surface or eventually in the posterior chamber.

ENDOPHTHALMITIS Endophthalmitis is a serious intraocular inflammation caused by infection. The incidence of endophthalmitis after cataract extraction and IOL implant is around 0.1%.62,63 This incidence rises by around fourfold in the case of posterior capsule rupture and anterior vitrectomy. The most common preventive measures currently adopted are: ƒƒ Wide-spectrum topical antibiotics (commonly a quinolone) a few days preoperatively and cleaning with pure povidone iodine of the skin and eyelids, and diluted 50% in the conjunctival sac a few minutes before surgery to reduce counts of conjunctival flora. ƒƒ Isolating the eyelids and lashes with tape ƒƒ Intracameral antibiotic: Cefuroxime has been found to cut the risk of endophthalmitis by fivefold but is ineffective against methicillin-resistant staphylococci, enterococci and pseudomonas. It also has to be reconstituted in a vial with the consequent risk of endophthalmitis. Moxifloxacin (Vigamox R, 0.1 ml) may also be used. In Europe, intracameral cefuroxime is most commonly used. Endophthalmitis symptoms are: considerable loss of vision, ocular pain (although 25% present without pain) and photophobia. The most common signs are: ƒƒ Conjunctival hyperemia ƒƒ Eyelid edema ƒƒ Anterior chamber turbidity with corneal edema and keratic precipitates ƒƒ Anterior chamber hypopion Absence of the red reflex due to substantial vitritis classifying postsurgery endophthalmitis: ƒƒ Hyperacute: fulminating infection whose onset is earlier than 24 hours, usually caused by Gram-negative bacteria (Pseudomonas aeruginosa) or pneumococcus. Prognosis is poor even after receiving adequate treatment. Fortunately its incidence is very low (Figs 19A and B). ƒƒ Acute: this is the most common form. It manifests between days 1 and 5 after surgery. Gram-positive organisms account for 80% (Staphylococcus

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226

A

B

Figures 19A and B  (A) Severe hyperacute endophthalmitis in a patient with cataract and vitreous hemorrhage. Caused by Streptococcus pneumoniae. Conducting an anterior approach vitrectomy due to poor visualization. Outcome poor despite complete treatment including three flushing attempts; (B) Endophthalmitis presenting 48 hours after surgery caused by Staphylococcus epidermidis. Note the hypopyon, corneal edema and vitreous infiltration behind the lens

epidermidis, Staphylococcus aureus). This form of endophthalmitis responds well to adequate diagnosis and treatment. ƒƒ Subacute: occurs after days 5–6 and before day 20 postsurgery. Symptoms are milder and it may respond well to treatment. ƒƒ Late onset: this form of endophthalmitis develops after a month and before a year has passed after surgery. The course of infection includes persistent red eye and uveitis responding to steroid treatment. The causative microorganism is usually Propionibacterium acnes.

Etiology Most infections secondary to cataract surgery are caused by Gram-positive bacteria. According to the US Endophthalmitis Vitrectomy Study,64 94.2% are caused by Gram-positive microorganisms, of which 70% are produced by S. epidermidis, 9.9% by S. aureus and 14.3% by other Gram-positive organisms. It should be noted that 100% of these causative agents are sensitive to vancomycin. Gram-negative microorganisms account for 6.5% of the cases, of which 89% respond to amikacin and ceftazidime. When a diagnosis of endophthalmitis is suspected according to the signs and symptoms described above, the first step is to obtain samples for microbial culture. Swabs taken from the conjunctiva, eyelids or cornea are of little use because of their variability. In contrast, a vitreous humor sample will return a positive result in close to 70% of the cases of infection. Aqueous humor provides a positive culture result in only 50% of the cases.65,66 Vitreous or aqueous humor samples will first inform the surgeons of whether the microorganism is Gram-positive or negative. If available, polymerase chain reaction is the most sensitive method for diagnosing endophthalmitis. If the bacteriological results are negative, then standard treatment is given and maintained according to

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

227 the signs and symptoms. In general, if the condition does not worsen, initial treatment is continued. Samples of vitreous humor may be obtained during surgery or on an outpatient basis. Topical or retrobulbar anesthesia is induced followed by the instillation of 5% povidone. A 22-gauge needle fitted to an insulin syringe is inserted 3.5–4 mm from the limbus penetrating 5–10 mm toward the eye center and 0.4 ml of vitreous humor are aspirated. In this operation, the first dose of wide-spectrum antibiotic is usually given.

Treatment In the clinical trial designed to evaluate treatment strategies in the Endophthalmitis Vitrectomy Study,67 no differences were detected in final visual acuity and ocular media transparency according to the use or not of systemic antibiotics (amikacin, ceftazidime). In patients with an initial visual acuity of light perception only, better results were obtained when a pars plana vitrectomy was immediately performed compared to intracameral antibiotics. Results indicated a threefold higher chance of a final visual acuity greater or equal to 0.5, a twofold chance of a visual acuity greater or equal to 0.05, and a halved risk of severe vision loss. In the case of a visual acuity of hand motion or better no differences were detected between immediate pars plana vitrectomy and tap biopsy. Intravitreal antibiotic injection is the best way to achieve high concentrations of antibiotic in the eye. The following doses of antibiotic should be administered in every endophthalmitis process: ƒƒ Intravitreal doses –– Vancomycin: 1 mg in 0.1 ml –– Ceftazidime: 2.25 mg in 0.1 ml –– If the patient is allergic to beta-lactams, amikacin can be given at 0.4 mg in 0.1 ml. Dexamethasone (0.4 mg in 0.1 ml) can be added. Other routes of administration may be added to the intravitreal injection. ƒƒ Subconjunctival –– Vancomycin: 25 mg in 0.5 ml –– Ceftazidime: 100 mg in 0.5 ml –– Dexamethasone: 6 mg ƒƒ Topical –– Vancomycin: 50 mg in 1ml –– Ceftazidime 100 mg in 1ml –– Amikacin 20 mg in 1ml –– Prednisolone acetate 1% every 2 hours ƒƒ General These agents penetrate inflamed eyes and attain potentially efficient doses after their intravenous administration. –– Vancomycin: 1 g every 12 hours

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228 –– Ciprofloxacin (750 mg every 12 hours); high concentrations of this antibiotic are achieved in the vitreous after its oral administration –– Ceftazidime (1 g every 12 hours). ƒƒ Infusion Drip If a vitrectomy is undertaken, the following antibiotics are added to the infusion saline. –– Gentamicin: 8 μ/ml (4 mg in 500 ml BSS) –– Vancomycin: 10 μ/ml (5 mg in 500 ml BSS) or clindamycin 9 μ/ml (4.5 mg in 500 ml BSS) –– Dexamethasone 64 μ/ml (32 mg in 500 ml BSS).

Vitrectomy The idea of conducting a vitrectomy is that it eliminates the microorganisms causing infection along with their toxins from the globe, improving the penetration of antibiotics and clearing the path of vision. Nevertheless, vitrectomy carries several risks, especially in cases of corneal opacity, presence of an IOL and substantial vitritis, apart from the risk of suffering retinal tears in surgery due to the inflammation and friability of the retina. The presence of retinal detachment considerably worsens the prognosis. A rate of 5% retinal detachments was detected in the Endophthalmitis Vitrectomy Study. Some surgeons recommend an anterior approach to vitrectomy to avoid vitreous traction at the pars plana.68 However, with the introduction of trocars (23/25 gauge systems), especially valved designs, less traction is generated on the peripheral retina making the pars plana vitrectomy a more suitable option. In addition, the posterior capsule can be spared (not all current IOLs are suitable for sulcus placement). Notwithstanding, in cases of poor visualization an anterior vitrectomy approach is practically mandatory.

Anterior Approach For an anterior approach, we use the incision made previously for cataract surgery and place another incision at the limbus separated by an angle of 170° to introduce 23/25-gauge instruments. First, a sample is taken from the anterior chamber and membranes on the iris and IOL is removed. Next, the posterior capsule is opened at the central level using the vitrector with irrigation and introducing the light pipe. This means we can perform the vitrectomy with only two port openings. A core vitrectomy is undertaken avoiding traction on the vitreous, and at the end of surgery, the antibiotics are introduced. If possible, the IOL is luxated to the sulcus in front of the capsulorhexis, to avoid its subsequent dislocation. In the case of a three-piece IOL we can try to trap the optics in the capsulorhexis, either leaving the haptics in the bag or simultaneously luxating them to the sulcus. If owing to the capsulotomy (normally the IOL does not adhere to the capsular remains) the lens is too unstable; for in the bag or sulcus

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

229 placement it is best to explant the lens and replace it, if not immediately in a subsequent operation.

Posterior Approach The possibility of placing a 6 mm infusion cannula or an infusion tube in the anterior chamber should be evaluated. We always include the antibiotics mentioned previously in the infusion fluid. Before opening the infusion line, we should ensure the fluid will not pass to the choroids, since some uveal effusion and hypotony or the presence of a peripheral dense exudate is relatively common in these cases. If the exit point of the infusion line cannot be seen, the introduction through the 23-gauge trocar of a 25/27 gauge needle to free the line is a helpful strategy. First, the fibrin membranes formed on the iris and lens are removed using intraocular membrane forceps. Once this has been done, greater dilation of the iris can be achieved or iris hooks can be used for good visualization of all maneuvers (Figs 20A and B). The vitreous sample can be obtained with the infusion line closed or preferably introducing air. Using a 5 ml syringe, the assistant collects a 0.3–0.5 ml sample of vitreous gel free of infusion fluid by manual aspiration for Gram staining and culture (Figs 21A and B). To do this, the syringe is connected to the vitrectome’s aspiration line and the sample is obtained as we cut the vitreous with vitrector. A core vitrectomy is performed behind the lens and we work backward at a high cutting rate and low aspiration power to avoid tractions and tears of the retina since it is highly friable. No traction should be exerted on the hyaloid for the same reason. As we approach the end of surgery, the doses of intravitreal antibiotics can be introduced. In all cases, good visualization is needed for the maneuvers.

Late-Onset Endophthalmitis This may occur from the first month postsurgery up until 1 year. Following a YAG capsulotomy, endophthalmitis can even appear later than a year. Muttonfat keratic precipitates in uveitis are a classic granulomatous presentation accompanied by a Tyndall effect and anterior vitreous cellularity. The appearance of typical saccular whitish plaques reminiscent of cortical remnants is more characteristic of Propionibacterium acnes infection. Besides frequent topical treatment with corticosteroids, wide-spectrum antibiotics and mydriatics, some authors have described the successful use in 30–50% of the cases of oral clarithromycin 500 mg/12 hours for 14 days (Fig. 22).69 A further therapeutic option described in the literature is Nd-YAG capsulotomy followed by intravitreal antibiotic injection.70 For cases refractory to treatment, we would proceed with intravitreal vancomycin. If ineffective, the course to follow would be a pars plana vitrectomy with flushing of the

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230

A

B

Figures 20A and B  (A) Removing inflammatory membranes from the anterior chamber affecting the iris and angle; (B) Appearance of the anterior chamber after freeing from membranes

A

B

Figures 21A and B  (A) Obtaining a sample of infiltrated vitreous for culture: the vitreotome is active and a 5 ml syringe is connected to the aspiration line; (B) Pressure is maintained by instilling air

Figure 22  Late-onset endophthalmitis. Note the deposits on the anterior lens surface

Chapter 10    Vitrectomy in Anterior Segment Surgery Complications

231 capsular bag with the aforementioned antibiotics, though in these resistant cases it is necessary to replace the IOL by means of a full capsulectomy and sacculectomy followed by IOL implant in the sulcus or anterior chamber. Our choice for this purpose would be an iris-fixated IOL.

REFERENCES 1. Kelman CD. Phacoemulsification and aspiration. A new technique of cataract removal. A preliminary report. Am J Ophthalmol. 1967;64(1):23-35. 2. Kelman CD. Phacoemulsification and aspiration. A report of 500 consecutive cases. Am J Ophthalmol. 1973;75(5):764-8. 3. Teichmann KD, Uthoff D. Retrobulbar (intraconal) anesthesia with a curved needle: technique and results. J Cataract Refract Surg. 1994;20(1):54-60. 4. Duker JS, Belmont JB, Benson WE, et al. Inadvertent globe perforation during retrobulbar and peribulbar anesthesia. Patient characteristics, surgical management, and visual outcome. Ophthalmology. 1991;98(4):519-26. 5. Fukasaku H, Marron JA. Pinpoint anesthesia: a new approach to local ocular anesthesia. J Cataract Refract Surg. 1994;20(4):468-71. 6. Fukasaku H. Sub-tenon´s pinpoint anesthesia. Ophthalmol Clin Nort Am. 1998;2:127-9. 7. Nouvellon E, Cuvillon P, Ripart J. Regional anesthesia and eye surgery. Anesthesiology. 2010;113(5):1236-42. 8. Davis DB, Mandel MR. Efficacy and complication rate of 16,224 consecutive peribulbar blocks. A prospective multicenter study. J Cataract Refract Surg. 1994;20(3):327-37. 9. Morgan CM, Schatz H, Vine AK, et al. Ocular complications associated with retrobulbar injections. Ophthalmology. 1988;95(5):660-5. 10. Edge KR, Nicoll JM. Retrobulbar hemorrhage after 12,500 retrobulbar blocks. Anesth Analg. 1993;76(5):1019-22. 11. Huber KK, Remky A. Effect of retrobulbar versus subconjunctival anaesthesia on retrobulbar haemodynamics. Br J Ophthalmol. 2005;89(6):719-23. 12. Goldsmith MO. Occlusion of the central retinal artery following retrobulbar hemorrhage. Ophthalmologica. 1976;153(3):191-6. 13. Kraushar MF, Seelenfreund MH, Freilich DB. Central retinal artery closure during orbital hemorrhage from retrobulbar injection. Trans Am Acad Ophthalmol Otolaryngol. 1974;78(1):OP65-70. 14. Burkat CN, Lemke BN. Retrobulbar hemorrhage: inferolateral anterior orbitotomy for emergent management. Arch Ophthalmol. 2005;123(9):1260-2. 15. Fishkind W. Complications in Phacoemulsification: Avoidance, Recognition, and management. New York: Thieme; 2002. p. 8. 16. Fishkind WJ. Unexpected vitrectomy as a complication of cataract surgery. J Cataract Refract Surg. 1994;20:54-7. 17. Osher RH, Cionni RJ. The torn posterior capsule: its intraoperative behavior, surgical management, and long-term consequences. J Cataract Refract Surg. 1990;16(4):490-4. 18. Powe NR, Schein OD, Gieser SC, et al. Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation. Cataract Patient Outcome Research Team. Arch Ophthalmol. 1994;112(2):239-52.

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232 19. Fishkind W. Complications in Phacoemulsification. Avoidance, Recognition, and Management. New York: Thieme; 2002. pp. 136-9. 20. Chalam KV, Gupta SK, Vinjamaram S, et al. Small-gauge, sutureless pars plana vitrectomy to manage vitreous loss during phacoemulsification. J Cataract Refract Surg. 2003;29(8):1482-6. 21. Shah VA, Gupta SK, Chalam KV. Management of vitreous loss during cataract surgery under topical anesthesia with transconjunctival vitrectomy system. Eur J Ophthalmol. 2003;13(8):693-6. 22. Michelson MA. Use of a Sheet´s glide as a pseudo-posterior capsule in phacoemulsification complicated by posterior capsule rupture. Eur J Implant Refract Surg. 1993;5:70-2. 23. Leaming DV. Practice styles and preferences of ASCRS members―1994 survey. J cataract Refract Surg. 1995;21:378-85. 24. Hutton WL, Snyder WB, Vaiser A. Management of surgically dislocated intravitreal lens fragments by pars plana vitrectomy. Ophthalmology. 1978;85(2):176-89. 25. Shapiro MJ, Resnick KI, Kim SH, et al. Management of the dislocated crystalline lens with a perfluorocarbon liquid. Am J Ophthalmol. 1991;112(4):401-5. 26. Lewis H, Blumenkranz MS, Chang S. Treatment of dislocated crystalline lens and retinal detachment with perfluorocarbon liquids. Retina. 1992;12(4):299-304. 27. Truhlsen SM. Approaching nucleus slippage. Arch Ophthalmol. 1991;109(5):627. 28. Weinstein GW, Charlton JF, Esmer E. The “lost lens”: a new surgical technique using the Machemer lens. Ophthalmic Surg. 1995;26(2):156-9. 29. Aaberg TM, Rubsamen PE, Flynn HW, et al. Giant retinal tear as a complication of attempted removal of intravitreal lens fragments during cataract surgery. Am J Ophthalmol. 1997;124(2):222-6. 30. Kim JE, Flynn HW, Smiddy WE. Retained lens fragments after phacoemulsification. Ophthalmology. 1994;101(11):1827-32. 31. Lai TY, Kwok AK, Yeung YS, et al. Immediate pars plana vitrectomy for dislocated intravitreal lens fragments during cataract surgery. Eye (Lond). 2005;19(11):115762. 32. Stark WJ, Worthen DM, Holladay JT, et al. The FDA report on intraocular lenses. Ophthalmology. 1983;90(4):311-17. 33. Smith SG, Lindstrom RL. Malpositioned posterior chamber lenses: etiology, prevention, and management. J Am Intraocul Implant Soc. 1985;11(6):584-91. 34. Gross JG, Kokame GT, Weinberg DV, et al. In-the-bag intraocular lens dislocation. Am J Ophthalmol. 2004;137(4):630-5. 35. Chan CK, Agarwal A, Agarwal S, et al. Management of dislocated intraocular implants. Ophthalmol Clin North Am. 2001;14(4):681-93. 36. Martínez-Castillo V, Elies D, Boixadera A, et al. Silicone posterior chamber phakic intraocular lens dislocated into the vitreous cavity. J Refract Surg. 2004;20(6):7737. 37. Mittra RA, Connor TB, Han DP, et al. Removal of dislocated intraocular lenses using pars plana vitrectomy with placement of an open-loop, flexible anterior chamber lens. Ophthalmology. 1998;105(6):1011-4. 38. Allara RD, Weinstein GW. A new surgical technique for managing sunset syndrome. Ophthalmic Surg. 1987;18(11):811-4. 39. Hara T, Hara T. Ten-year results of anterior chamber fixation of the posterior chamber intraocular lens. Arch Ophthalmol. 2004;122(8):1112-6.

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233 40. Zeh WG, Price FW. Iris fixation of posterior chamber intraocular lens. J Cataract Refract Surg. 2000;26(7):1028-34. 41. Condon GP. Simplified small-incision peripheral iris fixation of an AcrySof intraocular lens in the absence of capsule support. J Cataract Refract Surg. 2003;29(9):1663-7. 42. Stutzman RD, Stark WJ. Surgical technique for suture fixation of an acrylic intraocular lens in the absence of capsule support. J Cataract Refract Surg. 2003;29(9):1658-62. 43. Friedberg MA, Pilkerton AR. A new technique for repositioning and fixating a dislocated intraocular lens. Arch Ophthalmol. 1992;110(3):413-5. 44. Flynn HW, Buus D, Culbertson WW. Management of subluxated and posteriorly dislocated intraocular lenses using pars plana vitrectomy instrumentation. J Cataract Refract Surg. 1990;16(1):51-6. 45. Uthoff D, Teichmann KD. Secondary implantation of scleral-fixated intraocular lenses. J Cataract Refract Surg. 1998;24(7):945-50. 46. Lewis H, Sanchez G. The use of perfluorocarbon liquids in the repositioning of posteriorly dislocated intraocular lenses. Ophthalmology. 1993;100(7):1055-9. 47. Chang S, Coll GE. Surgical techniques for repositioning a dislocated intraocular lens, repair of iridodialysis, and secondary intraocular lens implantation using innovative 25-gauge forceps. Am J Ophthalmol. 1995;119(2):165-74. 48. Chan CK. An improved technique for management of dislocated posterior chamber implants. Ophthalmology. 1992;99(1):51-7. 49. Gabor SG, Pavlidis MM. Sutureless intrascleral posterior chamber intraocular lens fixation. J Cataract Refract Surg. 2007;33(11):1851-4. 50. Scharioth GB, Prasad S, Georgalas I, et al. Intermediate results of sutureless intrascleral chamber intraocular lens fixation. J Cataract Refract Surg. 2010;36(2):254-9. 51. Lindquist TD, Agapitos PJ, Lindstrom RL, et al. Transscleral fixation of posterior chamber intraocular lenses in the absence of capsular support. Ophthalmic Surg. 1989;20(11):769-75. 52. Ramocki JM, Shin DH, Glover BK, et al. Foldable posterior chamber intraocular lens implantation in the absence of capsular and zonular support. Am J Ophthalmol. 1999;127(2):213-6. 53. Oshima Y, Oida H, Emi K. Transscleral fixation of acrylic intraocular lenses in the absence of capsular support through 3.5 mm self-sealing incisions. 1998;24(9):1223-9. 54. Lane SS, Schwartz GS. Techniques of primary and secondary transscleral fixation of posterior chamber intraocular lenses. In: Fishkind WJ. Complications in Phacoemulsification. New York: Thieme; 2002. pp. 155-65. 55. van der Meulen IJ, Gunning FP, Vermeulen MG, et al. Artisan lens implantation to correct aphakia after vitrectomy for retained nuclear lens fragments. J Cataract Refract Surg. 2004;30(12):2585-9. 56. Mohr A, Hengerer F, Eckardt C. Retropupillary fixation of the iris claw lens in aphakia. 1 year outcome of a new implantation techniques. Ophthalmologe. 2002;99(7):580-3. 57. Baykara M, Ozcetin H, Yilmaz S, et al. Posterior iris fixation of the iris-claw intraocular lens implantation through a scleral tunnel incision. Am J Ophthalmol. 2007;144(4):586-91.

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234 58. Mönestam EI. Incidence of dislocation of intraocular lenses and pseudophakodonesis 10 years after cataract surgery. Ophthalmology. 2009;116(12):2315-20. 59. Davis D, Brubaker J, Espandar L, et al. Late in-the-bag spontaneous intraocular lens dislocation: evaluation of 86 consecutive cases. Ophthalmology. 2009;116(4):66470. 60. Hayashi K, Hirata A, Hayashi H. Possible predisposing factors for in-the-bag and out-of-the-bag intraocular lens dislocation and outcomes of intraocular lens exchange surgery. Ophthalmology. 2007;114(5):969-75. 61. Gimbel HV, Condon GP, Kohnen T, et al. Late in-the-bag intraocular lens dislocation: incidence, prevention and management. J Cataract Refract Surg. 2005;31(11):2193-204. 62. Peyman GA, Bassili SS. A practical guideline for management of endophthalmitis. Ophthalmic Surg. 1995;26(4):294-303. 63. Aaberg TM, Flynn HW, Schiffman J, et al. Nosocomial acute-onset postoperative endophthalmitis survey. A 10-year review of incidence and outcomes. Ophthalmology. 1998;105(6):1004-10. 64. Han DP, Wisniewski SR, Wilson LA, et al. Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study. Am J Ophthalmol. 1996;122(1):1-17. 65. Joondeph BC, Flynn HW, Miller D, et al. A new culture method for infectious endophthalmitis. Arch Ophthalmol. 1989;107(9):1334-7. 66. Peyman GA, Vastine DW, Raichand M. Experimental aspects and their clinical application. Ophthalmology. 1978;85(4):374-85. 67. Results of the Endophthalmitis Vitrectomy Study. A randomized trial of immediate vitrectomy and of intravenous antibiotics for the treatment of postoperative bacterial endophthalmitis. Endophthalmitis Vitrectomy Study Group. Arch Ophthalmol. 1995;113(12):1479-96. 68. Nieto UI, Corcóstegui GB, Paradinas MR. Tratamiento quirúrgico de las endoftalmitis: vías de abordaje. Resultados. Complicaciones. Arch Soc Esp Oftal. 1987;52:463-8. 69. Pellegrino FA, Wainberg P, Schlaen A, et al. Oral clarithromycin as a treatment option in chronic post-operative endophthalmitis. Arch Soc Esp Oftalmol. 2005;80(6):339-44. 70. Rojo A. Ferrer E, Torrón C, et al. Nd-YAG capsulotomy and intravitreal antibiotics as treatment of chronic endophthalmitis. Arch Soc Esp Oftalmol. 2000;75(2):109-16.

chapter 11

Eye Trauma Vitrectomy Joséfina Bañuelos Bañuelos, Patricia Martínez-García, Javier Orduña-Azcona, Ana Orive-Bañuelos, Alfonso Arias Puente

INTRODUCTION The ocular trauma may affect all globe structures and represents an important cause of blindness. There is no preference with respect to laterality and it affects more the young men. Vitrectomy is frequently required1 and the timing of surgery depends on the integrity of the eye wall. An open ocular trauma implies a rupture of the globe walls.2,3 Lesions can be multiple and in most cases they affect anterior and posterior chamber. Furthermore, they lead to an exposure of the ocular content to a septic environment with a high risk of endophthalmitis. In the case of blunt trauma, vitrectomy is directed to treat the complications: vitreous hemorrhage, glaucoma, retinal detachment (RD), alterations of the lens and macular involvement.

VITRECTOMY IN OPEN TRAUMATISMS Clinical History and Initial Examination In addition to recording the personal history and comorbidities which may interfere with the treatment, it is essential to ask when, where, how and with which object, the injury occurred. In cases of extensive wounds any manipulation that could provoke massive intraocular hemorrhage needs to be avoided.4 In addition to assessing the situation of the ocular media, it is essential to exclude the existence of endophthalmitis and the presence of an intraocular foreign body (IOFB). Orbital radiology is the most accessible method if a metallic foreign body is suspected. Once it has been confirmed, a CT should be

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236 carried out in order to localize the IOFB. If it is not metallic, nuclear magnetic resonance is indicated. Ultrasound should not be performed in an open eye injury.

Presurgical Considerations Once the eyeball has been evaluated, the following surgical questions need to be addressed: ƒƒ Assess whether the preparation and the available appliances are adequate to tackle the surgery and possible complications that may occur. If surgery can’t be delivered, the patient should be referred to another health provider4 Avoid the manipulation of the eyeball, the removal of protruding IOFB or forced opening of the lids. Occlude the eyeball and administer the first dose of systemic antibiotic. ƒƒ Whenever possible a hospital admission should be done as that encourages treatment compliance and a better relation with the patient. Generally patients are young people and anxious due to the high visual risk. They perceive a lower injury severity if they are sent home. ƒƒ General anesthesia is the preferred technique. It favors the wound closure and treatment of complications. Local anesthesia can be used to close small wounds if the patient is cooperative and later peribulbar anesthesia can be performed for vitrectomy. ƒƒ Treatment options: – Perform complete surgery in the initial intervention: close the ocular wound and perform vitrectomy. It has the advantage of reducing the risk of endophthalmitis, a better situation of the transparent media and lower costs. However, it increases the risk of intraoperative bleeding especially of posterior scleral wounds and the ciliary body. Generally, a skilled team will not be available to execute the surgery in 24 hours. – Perform the urgent ocular wound closure and later a vitrectomy. Then we will generally have better technical resources, a better eye evaluation and a lower risk of bleeding. However, we may have more opaque media due to a corneal edema or a progression of the crystalline opacity. The vitrectomy should be done as soon as possible, better within 4 days, to reduce the activation of vitreoretinal proliferation (VRP) factors and of endophthalmitis if there is an IOFB. But it can be delayed by up to 2 weeks if there is no risk of infection and depending on the nature of the trauma. It is preferable to postpone the surgery and wait for having qualified personnel and resources.4 The lack of light perception does not contraindicate surgery and it should not delay an initial reconstruction of the eyeball. Primary enucleation is only indicated if there is significant lack of tissue. The secondary enucleation is indicated in case of a painful blind eye unresponsive to treatment. Sympathetic ophthalmia is very rare and can occur days or decades after the trauma, but that

Chapter 11

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Eye Trauma Vitrectomy

237 is very unlikely. The threat of sympathetic ophthalmia is not an indication for enucleation of an eye with no light perception.4 ƒƒ Informed consent: you must specify the previous findings, treatment options, likely intraoperative complications, the need to modify the technique to new findings during the surgery, postoperative complications and the possibility of needing several interventions. The patient must know the purpose of the surgery: the need to close the eyeball, to remove the IOFB, to restore ocular anatomy, to prevent infection and to control inflammation. Functional recovery is secondary and often subject to intraoperative findings. It is important that the professional who informs the patient is familiar with the procedure to be able to answer the questions. Frequently, these patients claim medicolegal implications during or at the end of the process.

Surgical Technique Vitrectomy can be realized with 20, 23 or 25 gauge provided that you have these equipments at your disposal and accepting that it might be necessary to revert to a 20 gauge or even expand the incision further in case of an IFOB. In some cases accessory light might be required in order to exert the surgery bimanually. The infusion must be visualized before opening due to the risks of a detachment of the choroid or the retina. If required use a 6 mm infusion. However, if the opacity of the media persists, an infusion in the anterior chamber should be initially installed and once structures can be visualized, an infusion in the posterior segment can be installed. Avoid incisions close to traumatic scleral wounds. In these procedures wide-field systems are preferably used, like the binocular indirect ophthalmomicroscope system, in order not to be in contact with the eyes.5 If there is a corneal wound it is best to perform corneal suturing because it decreases the stromal edema and facilitates the visualization.4 If the edema is epithelial it can de-epithelialize (Not in diabetes or a history of recurrent erosion). In cases of severe corneal edema, corneal infiltration or hematocornea, temporary keratoprosthesis may be required,6,7 or if donor cornea is available the best technique is penetrating keratoplasty.8,9 In case of anterior lacerations, it can be frequently found blood in the anterior chamber, a hernia of the iris, miosis and fibrin if some hours have already elapsed. It is fundamental to wash the hyphema, to remove the membranes and to achieve pupil dilatation with epinephrine or iris retractors. Viscoelastic material is often required in order to keep the anterior chamber transparent and allow the surgery to continue. If there is no cataract or the opacity is small and thus we can perform a surgery, the extraction of the crystalline is not indicated. In case of an opacification or a rupture that prevents us from visualizing the posterior pole, the cataract needs to be removed. The morphology of traumatic cataracts plays

Step by Step Vitrectomy

238 an important role in determining the appropriate surgical technique and the final visual outcome.10-12 The phacoemulsification may only be performed in an anterior way if there is no risk of vitreous in the anterior chamber, subluxation by a zonular rupture or a posterior rupture causing tractions of the vitreous during the aspiration. This technique allows to avoid that residuals fall into the posterior chamber and to put an intraocular lens (IOL) into the capsular bag. In case of a soft lens with a rupture of both capsules, lensectomy of the crystalline can also be performed by vitrectomy via the anterior chamber. But it is preferable to perform it via pars plana, leaving a maximum of the anterior capsule in order to place a lens into the sulcus (Fig. 1). In case of a senile cataract and a firmer nucleus it is sometimes necessary to dislocate it to the posterior pole and to perform a lensectomy in the posterior chamber fragmenting the nucleus manually or with a phacofragmenter. If mechanical phacofragmentation is performed it is paramount to perform a complete vitrectomy in advance, in order to prevent tractions provoking new iatrogenic retinal lesions. In some cases, the lens must be removed during the intervention due to an increased opacity, an intraoperative lesion or in order to better complete the surgery. The patient must always be informed on this eventuality before starting the intervention. If the retina is severely affected and there is a high risk of anterior proliferative vitreoretinopathy (PVR), it is required to completely remove the lens, although it might be transparent or not bruised. Furthermore, executing a complete capsulectomy reduces the risk of anterior PVR and the evolution of phthisis. The placement of an IOL is not a priority in the surgery of ocular trauma. In case of severe traumas with significant affection of the retina, if the lens is not placed we will have less inflammation and a better visualization. The IOL needs to be acrylic due to the possibility of retinal complications. Generally

Figure 1

Posterior lensectomy

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239 we cannot carry out biometry in a perforated eye. Deferring the placement of the IOL to a second intervention will facilitate a more precise correction. After trauma, a zonular affection preceding the surgery is frequent and this risk is increased by the vitrectomy. There are an increased number of incidences of subluxation or of posterior luxation of the IOL and the capsular bag13 (Figs 2 and 3). When a perforating trauma exists (anterior and posterior laceration) and the posterior wound is not accessible, suture only the anterior perforation and defer the surgery. After 24 hours there may be a spontaneous sealing of the posterior laceration that may contain normal pressure during the vitrectomy (Fig. 4).

Figure 2

Intraocular silicone oil in ocular severe trauma

Figure 3

Oil extraction and insertion of intraocular lens

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240

Figure 4

Healed posterior laceration

The risk of reopening is higher in case of large wounds, elderly patients and high pressure during the vitrectomy. Cerclage placement is not paramount in urgent treatments because of the risks associated with ocular manipulation. There is no consensus on whether it should be used in all perforating traumas or posterior vitrectomies in particular, in case of media opacity. It can be beneficial to use a prophylactic laser. Cryotherapy on scleral or intraoperational lesions must be avoided as it increases the risk for PVR.14

SPECIAL SITUATIONS Trauma and Dense Vitreous Hemorrhage When we have an open trauma with a dense hemorrhage and high risk of retinal rupture, early vitrectomy needs to be executed in order to prevent the starting of PVR factors. It is important to avoid intraoperative hypotony because it increases the risk of rebleeding. If there is a risk of rebleeding or choroidal detachments, postoperative intraocular silicone may repress hemorrhage and prevent hypotony. In the absence of ocular laceration, the presence of post-traumatic intraocular hemorrhage does not imply emergency vitrectomy. It is of utmost importance to carry out ultrasound to rule out RD. If it starts to be reabsorbed and can be visualized, it is not necessary to operate the retina. If the retina cannot be visualized and the vitreous begins to organize, early vitrectomy is indicated due to the risk of PVR and RD.

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Trauma and Retinal Detachment The detachment of the retina associated with a perforating trauma represents a high risk factor for visual loss. As in any open injury, the question arises whether to do a complete surgical intervention or delay the vitrectomy in order to repair the RD. In addition, the detachment may be very different depending on if it is associated with a perforation, an IOFB or a burst of the eyeball, and if the lesions are unique or multiple and older or more recent. Performing an emergency surgery, including the closing of the ocular wound and to repair the detachment, has the advantage of reducing the incidence of endophthalmitis and the risk of PVR. If the vitrectomy is delayed there is a higher likelihood of a detachment of the posterior vitreous, especially significant in case of young patients. The recommendable delay should not be more than 1 week and it must not surpass 2 weeks. The PVR factor risks are: traumatic injury to the retina, presence and size of the IOFB, traumatic cataract, vitreous hemorrhage and preoperative visual acuity (AV).15 The use of intraocular silicone as the first choice reduces the early redetachment and limits the PVR, supports the positioning, and reduces rebleeding and the development of postoperative endophthalmitis16,17 (Fig. 5). In the complex post-traumatic detachments of the retina, partial retinectomy should be performed, or including 360° when there are severe previous PVR and subretinal fibrosis, large tears with contraction of the edges, and retinal incarceration of the scleral wound.18 It should be assessed if circular indentation is needed in order to fully secure the retinal detachment surgery. Risk of redetachment in these complex RD cases is 17–39%.17,18

Trauma and Intraocular Foreign Body About 40% of open eye injuries involve an IOFB. Most of the foreign bodies (FBs) are metallic (90%) and of these, 55–80% are magnetic. Also, more than half (65%) remain lodged in the vitreous cavity.19,20

Figure 5

Post-traumatic detachment and reparation with intraocular silicone oil

Step by Step Vitrectomy

242 Plain radiography has low sensitivity for IOFB. CT scan is the diagnostic technique of choice to locate metallic IOFB; it is fast, accessible and highly sensitive. You can spot sizes from 0.5 mm onwards, and the size gives information on the location and the condition of the eye wall. However, it does not detect fresh wood, ceramic or plastic. Ultrasound can detect any intraocular alteration, but this technique involves manipulating the eye and should be performed when the walls of the eyeball are already closed. In the presence of an ocular laceration with retention of IOFBs the Gold Standard technique is to intervene as soon as possible with closing of the wound and extraction of the FB applying vitrectomy. However, the criteria may vary depending on the risk of endophthalmitis. In case of no risk, the closure of the wound can be done first, followed by protection with systemic antibiotics and posterior vitrectomy with IOFB extraction. However, if the risk is high a complete urgency treatment is indicated with only one intervention. The risk is determined by the composition of the FB, the origin, the place where the trauma has occurred, the size and delay of the diagnosis.21-24 In addition to the risk of endophthalmitis there are other indications of delayed IOFB removal which are listed below: ƒƒ When human and technical resources are not available to perform the vitrectomy ƒƒ When there has not been the possibility of a prior workup to know the location of the IOFB ƒƒ When we have extensive wounds at the level of the ciliary body and no risk of endophthalmitis ƒƒ In perforating trauma with no accessible exit and FB in orbit. Wait for closure through cicatrization of the posterior wound before conducting the vitrectomy. It is not necessary to remove the orbit FB. ƒƒ The delay of vitrectomy also favors the detachment of the posterior vitreous, which allows better alimentation of the vitreous We must always maintain a correct and comprehensive coverage with antibiotics or conduct intravitreal antibiotic, respectively. For extraction of IOFB you must have an intraocular magnet and intraocular forceps that can adapt to different IOFB (Fig. 6). If the foreign body is on the retina or difficult to access, once freed from the vitreous it should be captured with the magnet and extracted with intraocular forceps. This bimanual technique is performed using the accessory light. Alternatively, the central vitreous can be illuminated with a microscope and the IOFB can be captured and extracted with the bimanual forceps (Fig. 7). However, the intraocular magnet does not have enough pull to allow the extraction through the aperture of the sclera and the IOFB could again fall on the retina. In case of retinal injuries caused by the impact of a FB, the retinectomy with choroidectomy on the edges of impact and complete removal of the vitreous significantly decreases the risk of retraction and PVR25 (Fig. 8).

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243

Figure 6

Figure 7

Magnet and intraocular forceps

Intraocular foreign body extraction with magnet and forceps

Figure 8

Macular impact. Intraocular oil

Step by Step Vitrectomy

244 If the foreign body is stuck in the sclera, it is likely that the perforation is complete. It is also likely that while capturing the IOFB a decompression of the globe will happen and the infusion has to be lowered. Generally, these wounds are not accessible to the suture. If you require a vitreous tamponade, better use silicone. It is important to assess the CT of the injured globe for the presence of a double perforation. This injury usually has a bad prognosis. About 14–26% of IOFB are associated with RD for traumatic retinal breaks, peripheral tears in the extraction, iatrogenic retinal ruptures and PVR. Factors associated with final AV are: preoperative visual acuity, size of the foreign body, posterior localization of the IOFB and presence of preoperative RD endophthalmitis, and timing of surgery.19,26, 27

Trauma and Endophthalmitis In an open eye trauma you have to be alert about the infection risk. The incidence of endophthalmitis in the diverse reports varies considerably (Table 1). The presence of corneal affection does not relate to the trauma, inflammation in the anterior chamber or hypopyon, vitreous involvement and endophthalmic retinopathy (perivascular infiltrates, hemorrhages and retinal edema), but it confirms the beginning or the existence of bacterial endophthalmitis.28 In the case of a clinical fungal infection, the clinical picture is more chronic, the infiltrated vitreous is more characteristic and it is generally associated with organic foreign bodies (Fig. 9). The most important risk factors are: the place where the trauma occurred (contamination), rural environment, delayed closure of the wound, age greater than 50 years, presence of IOFB, a lens rupture, and a filtering and dirty wound. The onset of endophthalmitis may be masked by injuries from the trauma and pain is not a paramount symptom except for Bacillus hyperacute disease pattern.29,30

TABLE 1 Incidence of endophthalmitis Yang et al Ophthalmologica 2010

(1981–2002) 41 years

12% endophthalmitis

Andreoli et al

Am J Ophthalmol 2009

675 patients

40 years

0.9% endophthalmitis

Colyer et al

Ophthalmology 2003–2005 2007 (Iraq)

27 years

0% endophthalmitis

Allen B

Ophthalmology 2003–2004 2005 (Iraq)

26.6 years 0% endophthalmitis

Mansouri et al

Retina 2009

22.5 years 5.1% endophthalmitis

1998–2003 (Iran)

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245 Antibiotic prophylaxis of endophthalmitis should be performed from the moment of the diagnosis whenever there is an open trauma in the absence of aseptic conditions. Extensive coverage with systemic and topical antibiotics should be conducted, adding clindamycin depending on the risk of anaerobic contamination. The use of intravitreal antibiotic is based on an individual decision (Box 1). Treatment of post-traumatic endophthalmitis is always surgical and vitrectomy is the treatment of choice. It must be assumed that the degree of difficulty of the intervention is greater and less predictable than in the postoperative endophthalmitis, the germs are usually more aggressive and the prognosis is worse.30,31 The media should be clarified, reducing corneal edema. If the cornea is strongly affected, temporary keratoprosthesis or a penetrating keratoplasty may be required. If the lens is integrated, it must be removed. An extensive capsulotomy needs to be conducted if there exists an IOL. The vitrectomy must be performed very carefully and slowly due to the risk of predamaged structures. Remove the FBs if any, remove all the affected vitreous and the maximum of pus. Do not induce posterior vitreous detachment if the vitreous is much attached and if the retina is necrotic. The internal limiting membrane (ILM) needs to be left for a second intervention. Intraocular silicone is used if there

Figure 9

Early endophthalmitis

Box 1: Antibiotic prophylaxis of endophthalmitis Vancomycin 1 g/12 (Anaerobic Gram-positive and Gram-positive) + (Clindamycin 600 mg/8 hour) (Anaerobic Gram-positive and Gram-negative) + Ceftazidime 1 g/12 (Gram-negative) or Fluoroquinolones: Levofloxacin or Moxifloxacin 400 mg/24 hour Systemic steroids Topical: Antibiotics (Moxifloxacin) + steroids + mydriatics

Step by Step Vitrectomy

246 has been a complete vitrectomy and there are associated lesions of the retina. It has the advantage of promoting infection control, keep the media clear and maintain the retina fixed. If you apply intravitreal antibiotics, use one quarter of the dose (Table 2).4

VITRECTOMY AND COMPLIACTIONS OF THE OCULAR TRAUMA Macular Hole The incidence is higher in young males and more frequent in blunt traumas with small objects and ocular contusion. The etiopathology of the traumatic macular hole is not known. It could be caused by a shock wave (this would explain its elliptic form) or by a sudden DVP (only 15% of the patients present associated DVP), traumatic necrosis of the fovea (edema and hemorrhage) or simply traction of the ILM at the moment of the impact. Though they may close spontaneously and it is recommended to wait for at least 3 months, the early surgery improves the visual acuity even in the presence of traumatic maculopathy.32,33

TABLE 2 Treatment for bacterial traumatic endophthalmitis Mode of injection

Name of the antibiotic

Dosage

Intravitreal

Ceftazidime Vancomycin Dexamethaxone

2.2 mg/0.1 ml 1–2 mg/0.1 ml 0.4 mg/0.1 ml

Liquids infusion

Ceftazidime Vancomycin Dexamethasone

2.2–25 mg/100 ml 25 mg/100ml 0.4–25 mg/100 ml

Subconjunctival (not tested)

Ceftazidime Vancomycin Dexamethasone

100 mg/0.5 ml 25 mg/0.5 ml 15 mg/1 ml

Topical

Fortified topical Prednisolone acetate 1% Moxifloxacin

Hourly

Oral

Moxifloxacin

400 mg/day

Intravenous

Ceftazidime Vancomycin Dexamethaxone

1 g/12 h 1 g/12 h 1–2 mg/kg/wt

(Source: Reproduced with permission from Kuhn F. Ocular Traumatology. Berlin: Springer, 2008)

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Ocular Hypotony and Bulb Phthisis This is the most severe complication because it implies a loss of the ocular anatomy. It can be caused by open traumas or by blunt traumas. It involves a loss of the function of the ciliary body with a decreased production of aqueous may be due to serous or chronic hemorrhagic detachment with or without RD, chronic inflammation or traction due to previous VRP. The vitrectomy is indicated to reapply the retina, extract the membrane structure, completely remove the lens and try to normalize the ocular anatomy. If the eye has functional viability, intraocular silicone should be placed into the posterior chamber. If you just want to keep the anatomy you must completely fill the eyeball. If there exists hypotony only, which does not improve with the treatment, and the vision deteriorates with the edema of the disk and chorioretinal folds (Fig. 11), the vitrectomy with the extraction of the ILM and intraocular gas may be sufficient to reverse the situation.34

Figure 10

Figure 11

Post-traumatic macular hole

Disk and macula edema

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248

REFERENCES 1. Peyman GA, Raichand M, Goldberg MF, et al. Vitrectomy in the management of intraocular foreign bodies and their complications. Br J Ophthalmol. 1980;64(7):476-82. 2. Kuhn F, Maisiak R, Mann L, et al. The Ocular Trauma Score (OTS). Ophthalmol Clin North Am. 2002;15(2):163-5. 3. Kuhn F, Morris R, Witherspoon CD, et al. The Birmingham Eye Trauma Terminology system (BETT). J Fr Ophtalmol. 2004;27(2):206-10. 4. Kuhn F. Ocular Traumatology. Berlin: Springer, 2008. 5. Kuhn F. Visualization issues in ocular trauma surgery. Retina Today. 2011:66-9. 6. Harissi-Dagher M, Dohlman CH. The Boston Keratoprosthesis in severe ocular trauma. Can J Ophthalmol. 2008;43(2):165-9. 7. Dong X, Wang W, Xie L, et al. Long-term outcome of combined penetrating keratoplasty and vitreoretinal surgery using temporary keratoprosthesis. Eye (Lond). 2006;20(1):59-63. 8. Yan H, Cui J, Zhang J, et al. Penetrating keratoplasty combined with vitreoretinal surgery for severe ocular injury with bloodstained cornea and no light perception. Ophthalmologica. 2006;220(3):186-9. 9. Roters S, Szurman P, Hermes S, et al. Outcome of combined penetrating keratoplasty with vitreoretinal surgery for management of severe ocular injuries. Retina. 2003;23(1):48-56. 10. Shah MA, Shah SM, Shah SB, et al. Effect of interval between time of injury and timing of intervention on final visual outcome in cases of traumatic cataract. Eur J Ophthalmol. 2011;21(6):760-5. 11. Pieramici DJ, Capone A Jr, Rubsamen PE, et al. Lens preservation after intraocular foreign body injuries. Ophthalmology. 1996;103(10):1563-7. 12. Kuhn F. Traumatic cataract: what, when, how. Graefes Arch Clin Exp Ophthalmol. 2010;248(9):1221-3. 13. Shah MA, Shah SM, Shah SB, et al. Comparative study of final visual outcome between open- and closed-globe injuries following surgical treatment of traumatic cataract. Graefes Arch Clin Exp Ophthalmol. 2011;249(12):1775-81. 14. Stone TW, Siddiqui N, Arroyo JG, et al. Primary scleral buckling in open-globe injury involving the posterior segment. Ophthalmology. 2000;107(10):1923-6. 15. El-Asrar AM, Al-Amro SA, Khan NM, et al. Retinal detachment after posterior segment intraocular foreign body injuries. Int Ophthalmol. 1998;22(6):369-75. 16. Nashed A, Saikia P, Herrmann WA, et al. The outcome of early surgical repair with vitrectomy and silicone oil in open-globe injuries with retinal detachment. Am J Ophthalmol. 2011, 151(3):522-8. 17. Azen SP, Scott IU, Flynn HW, et al. Silicone oil in the repair of complex retinal detachments. A prospective observational multicenter study. Ophthalmology. 1998;105(9):1587-97. 18. Kolomeyer AM, Grigorian RA, Mostafavi D, et al. 360º retinectomy for the treatment of complex retinal detachment. Retina. 2011;31(2):266-74. 19. Greven CM, Engelbrecht NE, Slusher MM, et al. Intraocular foreign bodies: management, prognostic factors, and visual outcomes. Ophthalmology. 2000;107(3):608-12.

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249 20. Williams DF, Mieler WF, Abrams GW, et al. Results and prognostic factors in penetrating ocular injuries with retained intraocular foreign bodies. Ophthalmology. 1988;95(7):911-6. 21. Colyer MH, Weber ED, Weichel ED, et al. Delayed intraocular foreign body removal without endophthalmitis during Operations Iraqi Freedom and Enduring Freedom. Ophthalmology. 2007;114(8):1439-47. 22. Thach AB, Ward TP, Dick JS, et al. Intraocular foreign body injuries during Operation Iraqi Freedom. Ophthalmology. 2005;112(10):1829-33. 23. Wani VB, Al-Ajmi M, Thalib L, et al. Vitrectomy for posterior segment intraocular foreign bodies: visual results and prognostic factors. Retina. 2003; 23(5):654-60. 24. Ahmadieh H, Soheilian M, Sajjadi H, et al. Vitrectomy in ocular trauma. Factors influencing final visual outcome. Retina. 1993;13(2):107-13. 25. Weichel ED, Bower KS, Colyer MH. Chorioretinectomy for perforating or severe intraocular foreign body injuries. Graefes Arch Clin Exp Ophthalmol. 2010;248(3):319-30. 26. Bai HQ, Yao L, Meng XX, et al. Visual outcome following intraocular foreign bodies: a retrospective review of 5-year clinical experience. Eur J Ophthalmol. 2011;21(1):98-103. 27. Jonas JB, Knorr HL, Budde WM, et al. Prognostic factors in ocular injuries caused by intraocular or retrobulbar foreign bodies. Ophthalmology. 2000;107(5):823-8. 28. Zhang Y, Zhang MN, Jiang CH, et al. Endophthalmitis following open globe injury. Br J Ophthalmol. 2010;94(1):111-4. 29. Alfaro DV, Roth D, Liggett PE. Posttraumatic endophthalmitis. Causative organisms, treatment, and prevention. Retina. 1994;14(3):206-11. 30. Chaudhry IA, Shamsi FA, Al-Harthi E, et al. Incidence and visual outcome of endophthalmitis associated with intraocular foreign bodies. Graefes Arch Clin Exp Ophthalmol. 2008;246(2):181-6. 31. Lieb DF, Scott IU, Flynn HW, et al. Open globe injuries with positive intraocular cultures: factors influencing final visual acuity outcomes. Ophthalmology. 2003; 110(8):1560-6. 32. García-Arumí J Corcostegui B, Cavero L, et al. The role of vitreoretinal surgery in the treatment of posttraumatic macular hole. Retina. 1997;17(5):372-7. 33. Yanagiya N, Akiba J, Takahashi M, et al. Clinical characteristics of traumatic macular holes. Jpn J Ophthalmol. 1996;40(4):544-7. 34. Ishida Y, Minamoto A, Takamatsu M, et al. Pars plana vitrectomy for traumatic cyclodialysis with persistent hypotony. Eye (Lond). 2004;18(9):952-4.

chapter 12

Basic Vitrectomy in Diabetic Retinopathy Jose Garcia-Arumi, Anna Boixadera, Laura Distefano, Vicente Martínez-Castillo, Miguel Angel Zapata

INTRODUCTION Diabetic retinopathy is the leading cause of blindness among working-age individuals in developed countries.1 Thirty-three percent of patients with type 1 diabetes and 17% with type 2 will develop proliferative retinopathy within 15 years of diabetes diagnosis,2 and 20% of patients with type 1 diabetes and 40% with type 2 will develop macular edema over a period of 10 years.3 Several complications of diabetic retinopathy require surgical man­ agement. Pars plana vitrectomy (PPV) has a number of established indications in diabetic patients yet others are still under discussion. Vitrectomy offers relief from retinal traction, clearing of media opacities, and stabilization of the proliferative process. Classic indications for PPV are vitreous hemorrhage, severe fibrovascular proliferation with tractional retinal detachment (TRD) affecting or threatening the macula, dense premacular hemorrhage and tractional-rhegmatogenous retinal detachment, whereas diffuse macular edema is a nonstandard indication for this procedure.4-6 However, diabetic macular edema (DME) associated with posterior hyaloid traction has been recently added as an indication for vitrectomy. 7 In addition, in patients with macular edema without a taut posterior hyaloid, vitrectomy surgery with or without internal limiting membrane (ILM) peeling has been reported.8 In general, improvements in surgical techniques instrumentation, and skills, have shortened the timing threshold for surgery and newly discovered benefits of early treatment continue to be described.9

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251

Surgical Approach First, a core three-port PPV is performed. A 6 mm cannula can be used in cases of extensive peripheral fibrosis or anterior retinal displacement that may obscure the cannula tip. Lensectomy can be added if lens opacity prevents adequate visualization or surgical access to the vitreous base. In eyes with complete vitreous separation, the usual indication is nonclearing vitreous hemorrhage; the vitreous is removed and this is followed by panretinal photocoagulation. If there is incomplete posterior hyaloid detachment, surgery is targeted at separating the posterior hyaloid. Several surgical techniques have been developed for membrane removal, such as segmentation, in which traction forces are eliminated by removing the posterior hyaloid and fibrovascular tissue connections to adjacent traction areas and isolating these independent segments (Figs 1A and B).7 Another technique is delamination, which involves cutting connections between the posterior hyaloid and/or fibrovascular tissue and the ILM (Figs 2A and B). In en bloc dissection, the vitreous and associated vitreoretinal membranes are removed as a single unit. The current technique

A

B

Figures 1A and B  Diagram showing the segmentation procedure: traction forces are eliminated by removing the posterior hyaloid and/or fibrovascular tissue connections to adjacent traction areas to isolate these independent segments

A

B

Figures 2A and B  Diagram showing how delamination is achieved: the connections are cut between the posterior hyaloid and/or fibrovascular tissue and the internal limiting membrane

Step by Step Vitrectomy

252 combines delamination and segmentation using a bimanual approach. For all these maneuvers, an accessory light may be needed, such as a 25-gauge xenon endoillumination probe through a fourth sclerotomy port. In eyes with incomplete posterior vitreous detachment and one or more focal adhesions, the cortical vitreous is identified, with or without the use of intravitreal triamcinolone, for a core vitrectomy.10 If there is wide separation between the vitreous and retina, the vitreous probe can be used to incise the posterior hyaloid in this region to gain access to the subhyaloid space. When a smaller separation exists, an opening can be made with a barbed microvitreoretinal (MVR) blade. Once the subhyaloid space is accessed, the opening is extended circumferentially 360° or minimally, depending on the degree of vitreous separation. This maneuver releases the peripheral vitreous from its posterior attachments, thus reducing the risk of iatrogenic retinal tears. Next, vitreoretinal proliferations and epiretinal membranes are addressed. Their dissection, which is usually initiated in the peripapillary region, can be conducted with the vitreous probe if there is adequate space between the vitreous and retina. If the separation cannot accommodate the probe, more detailed dissection using scissors, picks and/or forceps is required through a bimanual approach. Several radial cuts are made in the posterior hyaloid between focal areas of fibrovascular adhesion to extend the separation anteriorly. An additional surgical technique is viscodissection, which is used to increase the separation between the hyaloid or proliferative tissue. In this technique, small amount of hyaluronic acid is injected through a 40-gauge subretinal cannula (Fig. 3). A limitation of viscodissection is that one of the sclerotomies must be enlarged to 20-gauge if 23-gauge transconjunctival sutureless vitrectomy (TSV) is being done. We have designed a 23-gauge cannula for

Figure 3  Intraoperative fundus photograph showing the process of viscodissection: small amounts of hyaluronic acid is injected through a 40-gauge subretinal cannula to increase the separation between the hyaloid or proliferative tissue

Chapter 12    Basic Vitrectomy in Diabetic Retinopathy

253 viscodissection of 33-gauge caliber that will soon be available. Once focal adhesions are isolated, they are usually excised parallel to the retinal surface. If epiretinal membranes also exist, they are usually peeled toward the vascular epicenter and removed. After separation and removal of all posterior hyaloid and fibrovascular adhesions, the dissection is continued anteriorly. Broad vitreoretinal adhesions are more difficult to remove, particularly if they underlie retinal folds. In this case, the edge of the adhesion must be elevated, and each individual adhesion excised using membrane peeler cutter scissors. In eyes with no posterior vitreous separation, core vitrectomy is performed, but the subhyaloid space in the mid-periphery cannot be accessed using the vitreous cutter. This can be done in the peripapillary region using a barbed MVR blade. After making radial cuts, the hyaloid is stripped to the periphery in all quadrants. Blood beneath the posterior hyaloid can be aspirated using a soft-tipped cannula, the vitreous cutter, or if clotted, peeled with forceps. In some cases in which the retina is not completely reattached despite vitreoretinal dissection, a relaxing retinectomy may be required. The fibrovascular tissue over the optic disk is carefully removed with forceps (Fig. 4). After completing the vitrectomy, panretinal photocoagulation with or without cryotherapy of the sclerotomies is performed (Fig. 5). The peripheral fundus is then examined under scleral depression to search for possible iatrogenic retinal breaks before fluid-air exchange, when needed. Depending on the state of the retina after surgery, an extended tamponade of nonexpansible gas or silicone oil is left in the vitreous cavity. It should be noted that with 23-gauge TSV, injection of silicone oil is feasible. If silicone oil is used, all sclerotomies should be sutured (Figs 6 to 8). A recent variation of vitrectomy for proliferative diabetic retinopathy (PDR) is the use of intravitreally injected anti-VEGF medication as an adjuvant. One

Figure 4  Removal of a fibrovascular proliferation over the optic nerve using intraocular forceps

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254

Figure 5  Panphotocoagulation performed at the end of the vitrectomy

A

B

Figures 6A and B  (A) A 65-year-old man with severe tractional retinal detachment affecting the macula. Preoperative visual acuity was 20/400; (B) One month after 23-gauge transconjunctival sutureless vitrectomy with bimanual dissection and silicone oil tamponade, visual acuity was 20/100

A

B

Figures 7A and B  (A) A 25-year-old woman with traction-rhegmatogenous retinal detachment. Preoperative fundus photograph. Visual acuity was 20/200; (B) Three months after 23-gauge transconjunctival sutureless vitrectomy with bimanual dissection and gas tamponade, visual acuity was 20/60

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255

A

B

Figures 8A and B  (A) Tractional retinal detachment affecting the macula. Preoperative visual acuity was 20/400; (B) After 23-gauge transconjunctival sutureless vitrectomy with bimanual dissection, visual acuity was 20/100

such agent, bevacizumab 1.25 milligram, or ranibizumab 0.05 milligram, is injected into the vitreous cavity 2–5 days before PPV. This monoclonal antibody decreases bleeding during surgical dissection of fibrovascular membranes and inhibits the growth of new vessels. Its use also decreases surgical time and the incidence of postoperative recurrent vitreous hemorrhage, as well as improving final visual acuity.11 Certain complications can occur, as described by Arevalo et al.12 These authors reported a risk of TRD or its progression soon after intravitreal bevacizumab in patients with severe PDR. In our experience, the optimal effect of intravitreal anti-VEGF is achieved when vitrectomy is performed 2 days after the injection. Among the descriptions of 23-gauge TSV for diabetic retinopathy, Eckardt’s first article13 reports the outcome in 41 patients treated with 23-gauge TSV using the Dutch Ophthalmic Research Center system; of these patients, 11 had diabetic retinopathy. The author reported that the instruments are less flexible than in 25-gauge TSV, and noted that vitrectomy was still somewhat slower than for 20-gauge vitrectomy. In two cases of PDR, slight bleeding into the vitreous cavity occurred in the first few days after the operation. No case of postoperative hypotony was observed and Eckardt concluded that 23-gauge TSV seems to offer all the advantages of the minimally invasive TSV system developed by Fujii et al14 plus the benefits of larger, sturdier instrumentation. The characteristics of the vitreous probe, particularly the fact that the cutting tip is closer to the edge, facilitate dissection of the fibrovascular proliferations occurring in diabetic retinopathy. All the classic surgical maneuvers can be carried out with 23-gauge TSV. In addition, an accessory, the 25-gauge widefield endoillumination probe, can be placed on a fourth sclerotomy, permitting bimanual dissection. After the initial experience of Eckardt with 23-gauge TSV, Kim et al15 described a pilot study in 22 diabetic retinopathy patients. Among the indications, 11 were vitreous hemorrhage, 10 DME, and one TRD. Intraoperative suture placement was necessary in 7.5% and the authors reported no serious postoperative complications. This publication was followed by several reports of further pilot studies.16-19 Thus, Oshima et al17 compared a group of 33

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256 patients treated with 20-gauge PPV and 38 patients treated with 23-gauge TSV: significant differences were detected only in the operating time and need for sutures on the sclerotomies. A larger number of iatrogenic tears were produced at the entry sites with 23-gauge TSV, although the difference was not significant. In addition, better intraoperative fluid control was observed with 23-gauge TSV. In a prospective, randomized study of diabetic TRD comparing 34 patients treated with 20-gauge PPV and 47 patients with 23-gauge TSV, we noted that membrane dissection was possible using the vitreous probe in 82% of the patients in the 23-gauge group compared to only 25% undergoing 20-gauge PPV (p < 0.05). Sutures were required in 22% of the 23-gauge TSV patients versus 100% of the 20-gauge PPV patients (p < 0.05). No differences were recorded in postoperative visual acuity, operating time (although there was a trend toward shorter surgery duration with 23-gauge TSV), postoperative cataract, iatrogenic tears, or postoperative vitreous hemorrhage. Outcomes of 25-gauge PPV for the treatment of PDR also appear to be similar to those reported for 20-gauge vitrectomy in terms of effectiveness and safety.20,21 According to the Diabetic Retinopathy Vitrectomy Study,22 the timing of vitrectomy for severe vitreous hemorrhage should be within 3 months in patients with Type 1 diabetes and within 6 months in those with Type 2. Moreover, this study reported that 15% of eyes with TRD suffered severe visual loss (< 5/200) when surgery was not performed within 1 year (Figs 9A to D). Despite the indication based on the results of classic studies of up to 3 months and 6 months respectively for Type 1 and 2 diabetes, in our experience, prompt surgery avoids worsening functional results in severe cases. Postoperative complications include vitreous hemorrhage, which occurs in 29–75% of patients, depending on the series;23 the use of intravitreal gas is ineffective at decreasing the risk of this event.24 Other complications include a

A

B

Figures 9A to D  (A) Macular tractional retinal detachment in a patient with a preoperative visual acuity of 20/60 and; (B) Optical coherence tomography scan showing subfoveal fluid; (C) After 23-gauge transconjunctival sutureless vitrectomy with bimanual dissection, visual acuity was 20/30 and; (D) Optical coherence tomography revealed a normal foveal contour

Chapter 12    Basic Vitrectomy in Diabetic Retinopathy

257 rise in postoperative intraocular pressure to over 30 mm Hg, occurring in 35% of the patients in the first 48 postoperative hours,25 growth of new iris vessels, which takes place in 8–26% of phakic patients and 31–55% of pseudophakic patients,26 and the severe complication, anterior fibrovascular proliferation, which is seen in 13% of the patients.27 Intravitreal bevacizumab at the end of surgery may help decrease the rate of these postoperative complications, although the benefits of this measure remain to be proven. Ahn et al noted a significant decrease in early vitreous hemorrhage and a shorter vitreous clearing time in patients receiving intravitreal bevacizumab at the end of PPV compared to patients not given this intravitreal injection.28

VITRECTOMY FOR DIABETIC MACULAR EDEMA Vitreous changes leading to increased vascular permeability have been proposed as a cause of macular edema, such as destabilization by abnormal glycation and cross-linking of vitreous collagen, deposition of vascular factors in the premacular gel, and cell migration to the posterior hyaloid with subsequent contraction and macular traction. The observation that relieving mechanical traction on the macula reduces DME supports the indication for vitrectomy in such patients. Further, improved retinal oxygenation with an associated reduction in macular thickness suggests a potential benefit of surgery.29 In cases of diffuse macular edema, vitrectomy is only indicated when this edema is refractory to focal laser treatment and several intravitreal injections of triamcinolone or anti-VEGF. In cases of an attached posterior hyaloid without a thickened vitreous membrane, some authors have described benefits of vitrectomy with or without ILM peeling,8,30-34 although these patients show anatomic but not visual improvement35-38 and this indication for vitrectomy remains uncertain. Anti-VEGF or triamcinolone treatment can be left until after the completion of surgery. A good alternative to treat macular edema may be the use of sustained-release dexamethasone implants (OzurdexÒ), because of their longer-lived effect and the fact that the clearance time of the drug is unaffected by the vitrectomy as occurs with intravitreal injections. In cases of diffuse macular edema with a taut posterior hyaloid observed by ophthalmoscopy and optical coherence tomography, the benefits of surgery include opening, elevating, and removing the posterior hyaloid.7 The Diabetic Retinopathy Clinical Research Group has recently published the results of a trial conducted in 87 patients with clinical vitreomacular traction, moderate visual loss and a thickened macula. At the 6-month follow-up visit, 38% of the patients gained greater than or equal to 10 letters from baseline, while 22% lost greater than or equal to 10 letters compared to initial visual acuity. In most patients, a 50% reduction in central retinal thickness from baseline was achieved at the 12th month visit, but only in about half of the patients was central retinal thickness less than 250 microns.29 Although vitrectomy may lead to visual and anatomic improvements in patients with macular edema, further work is needed to address the benefits of this procedure.

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REFERENCES 1. Moss SE, Klein R, Klein BE. The 14-year incidence of visual loss in a diabetic population. Ophthalmology. 1998;105(6):998-1003. 2. Klein R, Klein BE, Moss SE, et al. The Wisconsin epidemiologic study of diabetic retinopathy. II. Prevalence and risk of diabetic retinopathy when age at diagnosis is less than 30 years. Arch Ophthalmol. 1984;102(4):520-6. 3. Klein R, Klein BE, Moss SE, et al. The Wisconsin epidemiologic study of diabetic retinopathy. XV. The long-term incidence of macular edema. Ophthalmology. 1995;102(1):7-16. 4. Mason JO, Colagross CT, Haleman T, et al. Visual outcome and risk factors for light perception and no light perception vision after vitrectomy for diabetic retinopathy. Am J Ophthalmol. 2005;140(2):231-5. 5. Helbig H, Sutter FK. Surgical treatment of diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol. 2004;242(8):704-9. 6. Mason JO, Colagross CT, Vail R. Diabetic vitrectomy: risks, prognosis, future trends. Curr Opin Ophthalmol. 2006;17(3):281-5. 7. Lewis H, Abrams GW, Blumenkranz MS, et al. Vitrectomy for diabetic macular traction and edema associated with posterior hyaloidal traction. Ophthalmology. 1992;99(5):753-9. 8. Rosenblatt BJ, Shah GK, Sharma S, et al. Pars plana vitrectomy with internal limiting membranectomy for refractory diabetic macular edema without a taut posterior hyaloid. Graefes Arch Clin Exp Ophthalmol. 2005;243(1):20-5. 9. Sullu Y, Hamidova R, Beden U, et al. Effects of pars plana vitrectomy on retrobulbar haemodynamics in diabetic retinopathy. Clin Experiment Ophthalmol. 2005;33(3):246-51. 10. Sakamoto T, Miyazaki M, Hisatomi T, et al. Triamcinolone-assisted pars plana vitrectomy improves the surgical procedures and decreases the postoperative bloodocular barrier breakdown. Graefes Arch Clin Exp Ophthalmol. 2002;240(6):423-9. 11. Zhao LQ, Zhu H, Zhao PQ, et al. A systematic review and meta-analysis of clinical outcomes of vitrectomy with or without intravitreal bevacizumab pretreatment for severe diabetic retinopathy. Br J Ophthalmol. 2011;95(9):1216-22. 12. Arevalo JF, Maia M, Flynn HW, et al. Tractional retinal detachment following intravitreal bevacizumab (Avastin) in patients with severe proliferative diabetic retinopathy. Br J Ophthalmol. 2008;92(2):213-6. 13. Eckardt C. Transconjunctival sutureless 23-gauge vitrectomy. Retina. 2005; 25(2):208-11. 14. Fujii GY, De Juan E, Humayun MS, et al. A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology. 2002; 109(10):1807-12. 15. Kim MJ, Park KH, Hwang JM, et al. The safety and efficacy of transconjunctival sutureless 23-gauge vitrectomy. Korean J Ophthalmol. 2007;21(4):201-7. 16. Arumí JG, Boixadera A, Martínez-Castillo V, et al. Transconjunctival sutureless 23-gauge vitrectomy for diabetic retinopathy. Review. Curr Diabetes Rev. 2009;5(1):63-6. 17. Oshima Y, Shima C, Wakabayashi T, et al. Microincision vitrectomy surgery and intravitreal bevacizumab as a surgical adjunct to treat diabetic traction retinal detachment. Ophthalmology. 2009;116(5):927-38.

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259 18. da R Lucena D, Ribeiro JA, Costa RA, et al. Intraoperative bleeding during vitrectomy for diabetic tractional retinal detachment with versus without preoperative intravitreal bevacizumab (IBeTra study). Br J Ophthalmol. 2009; 93(5):688-91. 19. Yang SJ, Yoon SY, Kim JG, et al. Transconjunctival sutureless vitrectomy for the treatment of vitreoretinal complications in patients with diabetes mellitus. Ophthalmic Surg Lasers Imaging. 2009;40(5):461-6. 20. Schoenberger SD, Miller DM, Riemann CD, et al. Outcomes of 25-gauge pars plana vitrectomy in the surgical management of proliferative diabetic retinopathy. Ophthalmic Surg Lasers Imaging. 2011;42(6):474-80. 21. Farouk MM, Naito T, Sayed KM, et al. Outcomes of 25-gauge vitrectomy for proliferative diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol. 2011;249(3):369-76. 22. Early vitrectomy for severe vitreous hemorrhage in diabetic retinopathy. Two-year results of a randomized trial. Diabetic Retinopathy Vitrectomy Study report 2. The Diabetic Retinopathy Vitrectomy Study Research Group. Arch Ophthalmol. 1985;103(11):1644-52. 23. Tolentino FI, Cajita VN, Gancayco T, et al. Vitreous hemorrhage after closed vitrectomy for proliferative diabetic retinopathy. Ophthalmology. 1989;96(10):1495-500. 24. Joondeph BC, Blankenship GW. Hemostatic effects of air versus fluid in diabetic vitrectomy. Ophthalmology. 1989;96(12):1701-6. 25. Han DP, Lewis H, Lambrou FH, et al. Mechanisms of intraocular pressure elevation after pars plana vitrectomy. Ophthalmology. 1989;96(9):1357-62. 26. Rice TA, Michels RG, Maguire MG, et al. The effect of lensectomy on the incidence of iris neovascularization and neovascular glaucoma after vitrectomy for diabetic retinopathy. Am J Ophthalmol. 1983;95(1):1-11. 27. Lewis H, Abrams GW, Foos RY. Clinicopathologic findings in anterior hyaloidal fibrovascular proliferation after diabetic vitrectomy. Am J Ophthalmol. 1987;104(6):614-8. 28. Ahn J, Woo SJ, Chung H, et al. The effect of adjunctive intravitreal bevacizumab for preventing postvitrectomy hemorrhage in proliferative diabetic retinopathy. Ophthalmology. 2011;118(11):2218-26. 29. Diabetic Retinopathy Clinical Research Network Writing Committee, Haller JA, Qin H, et al. Vitrectomy outcomes in eyes with diabetic macular edema and vitreomacular traction. Ophthalmology. 2010;117(6):1087-93.e3. 30. Dillinger P, Mester U. Vitrectomy with removal of the internal limiting membrane in chronic diabetic macular oedema. Graefes Arch Clin Exp Ophthalmol. 2004;242(8):630-7. 31. Ikeda T, Sato K, Katano T, et al. Vitrectomy for cystoid macular oedema with attached posterior hyaloid membrane in patients with diabetes. Br J Ophthalmol. 1999;83(1):12-4. 32. La Heij EC, Hendrikse F, Kessels AG, et al. Vitrectomy results in diabetic macular oedema without evident vitreomacular traction. Graefes Arch Clin Exp Ophthalmol. 2001;239(4):264-70. 33. Tachi N, Ogino N. Vitrectomy for diffuse macular edema in cases of diabetic retinopathy. Am J Ophthalmol. 1996;122(2):258-60.

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260 34. Yamamoto T, Hitani K, Tsukahara I, et al. Early postoperative retinal thickness changes and complications after vitrectomy for diabetic macular edema. Am J Ophthalmol. 2003;135(1):14-9. 35. Figueroa MS, Contreras I, Noval S. Surgical and anatomical outcomes of pars plana vitrectomy for diffuse nontractional diabetic macular edema. Retina. 2008;28(3):420-6. 36. Mochizuki Y, Hata Y, Enaida H, et al. Evaluating adjunctive surgical procedures during vitrectomy for diabetic macular edema. Retina. 2006;26(2):143-8. 37. Patel JI, Hykin PG, Schadt M, et al. Pars plana vitrectomy with and without peeling of the inner limiting membrane for diabetic macular edema. Retina. 2006;26(1):5-13. 38. Hoerauf H, Brüggemann A, Muecke M, et al. Pars plana vitrectomy for diabetic macular edema. Internal limiting membrane delamination vs posterior hyaloid removal. A prospective randomized trial. Graefes Arch Clin Exp Ophthalmol. 2011;249(7):997-1008.

chapter 13

Macular Surgery Amparo Navea, Elena Palacios, Carmen Desco, Jorge Mataix

SURGERY ON THE SURFACE OF THE MACULA This surgery is performed to treat several diseases: epiretinal membranes (ERM), vitreomacular traction syndrome, macular edema of a vascular origin (diabetic, vein occlusion), inflammatory macular edema (Irvine-Gass, uveitic), and macular hole (MH).

PRELIMINARY CONSIDERATIONS The clinical case should be studied attempting to determine the pathology requiring surgery. A good clinical history makes it possible to distinguish the primary retinal causes of the ERM, for example, vascular causes and cystoid macular edema following cataract surgery, vitreous interface diseases like MH and vitreomacular traction syndrome. The former conditions may have a poor visual prognosis due to the underlying retinal disease, while in the latter the membranes may be more closely adhered, thinner, and difficult to remove. Determination of the factors will help us to explain the prognosis to the patient and have an idea of what we will find during surgery. The retina should be carefully studied in order to examine the macula and observe the extent of the puckers; the edges of the ERM should be studied if they are visible, as should the contraction centers, the condition of the vitreous, and the cystic or noncystic appearance of the fovea. It is important not to forget to examine the peripheral retina: an open or treated tear can have generated an ERM which would contain cells from the retinal pigment epithelium and supposedly the surgery would be easier. An optical coherence tomography will show the points of adhesion of the membrane as well as the state of the retina, the degree of edema or atrophy

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262 which could contraindicate surgery if it is severe, as can be found in some forms of dry macular degeneration, since no visual improvement would be obtained.1 The crystalline lens should be evaluated. This lens can be preserved in the case of phakic patients so long as there is clear visualization of the macula during biomicroscopic stereoscopic examination. If there are central opacities or nuclear sclerosis that distort vision of the posterior pole, cataract surgery will have to be associated; this could be performed during the same operation or beforehand. If cataract surgery is not performed, the patient will have to be informed that he/she will probably need the operation some months afterward. Combined phakovitrectomy surgery has the advantage of saving the patient I operation. However, it does have some disadvantages. Although it is taken for granted that cataract surgery is a well mastered technique, awkward problems can arise during posterior vitrectomy (corneal edema, a pupil tending to contract, incisions that are not wholly sealed with flattening of the chamber) which will make the vitrectomy more tricky than if the two operations were performed separately. A possibly higher degree of postoperative inflammation should be expected and the appearance of pupillary synechiae should be watched out for as they are more frequent when the operations are associated. Separating the operations has the obvious disadvantage of making the patient go through surgery twice. Another point to be taken into account is that performing phacoemulsification on a vitrectomized eye is usually more difficult than on an eye with an integral vitreous.

INTERVIEW WITH THE PATIENT As in all medical activity, it is important to talk to the patient and explain what he/she may expect from the surgery. Macula surgery can lead to unwelcome postoperative surprises. The patient should know that the possibilities of visual recovery are generally uncertain and are related to the length of time their disease has been developing and the visual loss he/she has already undergone; the greater both of these are, the worse the visual prognosis. Nonetheless, they are not processes that tend to resolve spontaneously; therefore surgical treatment should be indicated promptly after diagnosis.2 The explanation should cover several aspects: ƒƒ Visual recovery associated with primary disease, time elapsed, and extent of visual loss ƒƒ Decrease in symptomatology: metamorphopsia or central scotoma depending on the postoperative retinal recovery. A certain degree of residual metamorphopsia may remain for some time or indefinitely ƒƒ Recovery period: retinal remodeling processes take their time and recovery of vision can be seen after months and years if long-term follow-up is performed. Nonetheless, a relative improvement is usually observed 1 month after surgery in the best cases

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263 ƒƒ Crystalline lens treatment in phakic patients: simultaneity of crystalline

lens surgery or its probable necessity in the months after vitrectomy will have to be explained ƒƒ The patient should be told about the need of postoperative postural rest, if it should be applied.

SURGERY PREPARATION A vitrectomy is programmed or not with cataract surgery. The size of the ports can be chosen in accordance with the surgeon’s preference. We find 23-gauge surgery very balanced and is what we usually use.

Technical Requirements A vitrectomy system, a wide field visualization device and visualization of the macula with high definition, such as the Mackemer magnifying macular contact lens or the high-resolution contact or noncontact lens, microforceps, dyes.

Human Requirements An experienced retinal surgeon is required. The work on the surface of the retina requires skill and training. It is difficult.

Patient Preparation The usual premedication for retina surgery will include pupillary dilation, sedation, and local anesthesia. The patient should be as comfortable as possible on the operating table so that he/she can keep still during surgery. The area should be cleansed with povidone and the areas should be sterile with an adhesive dressing holding eyelashes.

Surgeon Preparation The surgeon should be sitting properly in the surgeon’s seat. Macula surgery requires precision and a steady hand which is impossible if the surgeon is not sitting properly or if his/her arms are not supported, therefore the points that support the arms must be checked. The eyepieces, the height of the table, the microscope, and the surgeon’s seat should be suitably positioned. Check the position of the patient’s head. The plane of the patient’s face should be parallel with the floor so that the cornea is centered in the palpebral fissure and it should be possible to tilt the eyeball in order to have access to the upper and lower retinal periphery. Likewise, the sterile cloths and drapes should be correctly positioned. Work with little light during the vitrectomy requires that each drape be appropriately positioned and that there be no folds which could inadvertently

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264 limit the movements of the instruments, particularly at the inner and outer edges where the active terminals of the surgeon’s intraocular work move.

VITRECTOMY ƒƒ Position the microcannulas and the infusion line or perform the

ƒƒ

ƒƒ

ƒƒ ƒƒ

ƒƒ

sclerotomies if the former is not used, try to separate the incisions sufficiently for the instruments so that there is good intraocular mobility. Placement slightly above the horizontal meridians (some 150° of separation) is a comfortable position. Put on the wide field visualization system and start the vitrectomy Perform a mid-and peripheral vitrectomy. The length of time to be devoted to this part of the surgery is debatable: in the case in which there is no disease at the base of the vitreous body, it will probably not be necessary to eliminate the vitreous wholly. It is, however, advisable to eliminate it from the entry canal of the instruments to avoid subsequent incarcerations. At this point, the whole peripheral retina can be examined to detect any conditions that could need treatment Detach the hyaloid membrane if it was not already detached. Once the central vitreous has been removed, go deeper into the papilla to reduce the amount of vitreous cortex. Deactivate the vitrectomy blade and position the head on the edge of the papilla, preferably the nasal area, perform suction to try to grasp the posterior hyaloid membrane, swing the vitreotome horizontally to induce detachment. Repeat several times until achieved. Once it is detached, complete the vitrectomy halfway down or to the vitreous base Observe the macula: Decide whether to use dye and, if so, which to use Decide whether visualization is good or if macular lenses should be used Dye: There are different types; the one we use most is bright blue. It is loaded into a 2 cc syringe connected to a silicone tipped cannula which is injected directing the flow toward the posterior pole. When using microcannulas incorporating valves, it is not absolutely necessary to close up the infusion line as turbulence decreases considerably. After 1 minute we remove the coloring with a silicone tipped cannula connected to the extrusion needle or with the vitreotome Replace the lens if necessary. If we use a magnifying contact lens, the microscope head should be moved to a lower setting (as it will be focused for wide-field lenses). Start by focusing it approximately and, after introducing the microforceps and being able to see them through the pupil, adjust the fine focus and magnify the image. Unless you are very used to this procedure, care should be taken because of the drastic reduction in field produced by these lenses. To avoid involuntary intraocular contact, it is advisable to keep the ends of the two active instruments visible at all times through the pupil from the time they are introduced into the eye

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265 ƒƒ Peel away the membrane. Finding the edge or peeling plane of the membrane

is the most difficult maneuver in this operation; the second most difficult is not letting it go. If the edge of the membrane can be seen, which not the usual case is, it can be peeled back and removed entirely. When the edge is not visible, which is the usual case; there are several ways to proceed. Although there are reports of Tano’s brush for “scraping” the surface of the retina, it is difficult to find a plane without knocking it and causing bleeding. It may be a question of pinching the membrane and peeling it back until it tears which would give us a flap, going about it in the same way as one would to perform a capsulorhexis directly with forceps in cataract surgery. For this maneuver, try to choose an area where the membrane is thicker, for example where there are more puckers or a contraction center, or near or over one of the macular vessels. With the hand well-supported, open the forceps slightly and touch the surface of the membrane, depress it slightly, close the forceps without making a vertical movement and then pull gently upward once the membrane has been grasped. It usually tears thus providing a flap that can be dissected. It seldom comes away in one piece so it is dissected from the whole macula or part of it. If the dye has worked well, it is easier to find an edge as the membrane will be more “visible”. A membrane flap can also be created by using a vitrectomy surgical blade to make a linear incision and then using the forceps to remove it ƒƒ Once the membrane plane has been found, it should be dissected with the forceps. This maneuver should be performed by pulling the membrane tangentially over the retina centripetally. At this point in surgery, we should observe both the point of the membrane we are peeling and also the head of the forceps simultaneously. The head of the forceps should be situated in front of the point the membrane is being peeled away from; care must be taken or the retina could be knocked and torn. One of the most delicate steps is separating the membrane from the fovea. Care should be taken in performing this centripetally and very gently to avoid tearing the retina, especially if it is a cystic fovea. In some cases, there are friable membranes that tear and shred during dissection. They usually stay joined to the fovea and can be dissected from the perifoveal retina and, at the end, cut where they are joined to the fovea with the vitreotome ƒƒ Once the central membrane has been dissected, further dissection around the macula should be carried out ƒƒ To complete the operation, replace the wide-field system to check the peripheral retina, make a small final central vitrectomy and a partial or total air exchange.

SPECIFIC TECHNICAL POINTS IN MACULAR HOLE The technique is same, although special care should be taken in examining the peripheral retina as a greater incidence of detached retina after MH surgery

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266 has been reported than in ERM surgery.3 The inner limiting membrane (ILM) should be removed, using the same technique as for ERM, up to the edges of the hole. Further dissection of ILM beyond the vascular arches, or even inside them with a distance of 1 disk around the anatomic macula, is not necessary. Peeling the ILM is probably the most difficult part of macula surgery. At the end of the surgery a more complete air exchange should be done and the appropriate tamponade should be chosen. If the patient is not going to keep a facedown position, the C3F8 provides a longer-lasting, effective tamponade so long as the posture of the head is upright. If the patient can tolerate being facedown for some days, SF6 may be better. In cases of macular atrophy, silicone oil may be more useful.

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SURGERY IN THE SUBRETINAL MACULAR SPACE This type of surgery in the 90s was indicated for extracting subretinal neovascular membranes. Currently it has few, but necessary indications: serious submacular hemorrhage and foveal perfluorocarbon (PFC) liquid bubbles. An option for a relatively easy treatment of submacular hemorrhage consists of using combined recombinant tissue plasminogen activator (r-TPA) 25–50 µg/0.1 ml with gas.4 Recombinant tissue plasminogen activator injection of 0.1 cc followed by 0.3 cc of pure SF6 into the vitreous cavity, with the patient lying on his/her back for the first 6–8 hours so that the r-TPA can spread toward the clot and liquefy it, then the patient should lie facedown so that the gas can move the blood away from the macula. Perform a central vitrectomy and inject 0.1 ml of r-TPA solution under the retina using 38 or 40-gauge microcannulas needles. You can either wait 45–60 minutes for clot lysis and remove it by suction once it has liquefied, or you can inject pure SF6 and position the patient facedown, some hours after surgery. We have little and bad experience with these procedures. There is no large series that compares the injection of r-TPA and gas as opposed to vitrectomy although some short series give a better visual result with surgery in cases associated with age-related macular degeneration (AMD), which can also be used to remove the neovascular membrane that may be present.5 Regarding the surgical removal of these hemorrhages, the general points of macular surgery described above can also be applied to submacular surgery. It is indicated in circumstances in which the collection of subretinal substances can compromise vision. Natural evolution of big submacular hemorrhages leads to a very poor visual acuity because of both, the toxic effect of blood and also the subsequent fibrosis associated with exudative-AMD cases (Figs 1 to 4). Different situations may be encountered:

SEVERE SUBMACULAR HEMORRHAGE LOCATED INTO THE MACULAR AREA It should not extend to the periphery: perform a vitrectomy, use a fine-tipped cannula (38–40 gauge) connected to an injection system, perforate the retina and detach it injecting balanced salt solution (BSS). Then introduce the subretinal angled forceps through the retinotomy and extract the clot with care. It is enough just to free the fovea, it is not necessary to clean the whole subretinal space. If signs of new hemorrhaging are observed, intraocular pressure should be increased. To finish, perform an air exchange and use this or gas as a tamponade. It is not necessary to treat the posterior retinotomies with laser. An anti-VEGF injection can be added when finishing in the case in which hemorrhaging has occurred in AMD in order to help the lesion to heal up, unless it is due to tearing of a pigment epithelium detachment which is, in fact, quite usual in these cases.

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Figure 1  Patient I: submacular hemorrhage, observe the blood collecting under the macula before the surgery

Figure 2  Patient I: month after surgery

It is important to make a careful choice of the site for performing the retinotomy. This should be above and to the right of the fovea (as we look at the eye in the operating theater through the microscope, it will be upper temporal in the right eye and upper nasal in the left eye for right-handed surgeons), at a point at which the macula is damaged as little as possible, but which lets us reach under the fovea with the forceps. If we are very close we will run the risk of inducing macular scotomas and tears, on the other hand if we are not close enough the retina could be ripped by the forceps when trying to grasp the subfoveal clot.

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Figure 3  Patient II: another case of unilateral submacular hemorrhage

Figure 4  Patient II: spontaneous evolution 6 months of follow-up. Patient rejected the treatment

MASSIVE SUBRETINAL HEMORRHAGE THAT ALSO AFFECTS THE MACULA In these cases, the crystalline lens should be removed in phakic patients, a complete vitrectomy should be performed, a wide 100–180° temporal peripheral retinotomy along with the extraction of the clots with forceps and a vitreotome, application of the retina and laser and tamponade with silicone oil.

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SUBFOVEAL PERFLUOROCARBON BUBBLES Subretinal PFC bubbles do not require treatment, except those situated subfoveally or on the macula and which are very symptomatic. If they are not subfoveal, they can be extracted by piercing the retina with a thin cannula and suctioning, or using a vitrectomy blade and making a small incision in the direction of the retinal fibers and suctioning.6 If the bubbles are below the fovea, they cannot be extracted by using the technique described above without damaging it. In these cases, a detachment of the retina reaching the macula should be induced and a partial exchange of liquid-air should be performed leaving half the eye full of air; the patient should adopt a sitting position for a couple of days to move the bubbles downward. This technique can also be used for the treatment of postoperative retinal folds that affect the fovea. It is not easy to induce a voluntary retinal detachment, but it can be achieved in several ways. The one we use is as follows: connect a cannula with a 40-gauge tip to a silicone injection system with a syringe filled with BSS. This procedure makes it possible to direct a fine jet of liquid hard against the surface of the retina. The cannula is introduced into the eye and the point is placed in contact with the retina without pressing the point chosen. Maintaining the position, the liquid is injected; a blister usually forms and the retina detaches little by little. The tip of the cannula should be maintained into the created retinotomy without enlarging it, otherwise the liquid injected will reflow to the vitreous cavity and a large enough detachment would not be obtained. More than one separate injection often has to be applied. The first should be near the macular area outside the macular vessels, so that the macula can be detached but does not tear. We will keep injecting BSS till no further detachment can be induced. At this point, the macula can or cannot be detached. If not still detached, we will change tools and proceed to perform several air-fluid exchanges which will push the subretinal liquid toward the posterior pole (exactly what we do not want to happen when we operate on a detachment with adhered macula). The subfoveal bubble should not be attempted to be removed with instruments, as they are difficult to visualize once the retina is detached. Moreover, the fovea may tear if the subretinal space is suctioned. There are more situations besides those we have described in which macular surgery is indicated; detailing them all does not fall within the scope of this practical manual. However, the techniques described here cover the great majority of the cases we treat at present. In the future, there will probably be other possibilities available. On the other hand, we observe that old techniques, like removing subretinal membranes, are still useful in a few complex present day cases.

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REFERENCES 1. Mirza RG, Johnson MW, Jampol LM. Optical coherence tomography use in evaluation of the vitreoretinal interface: a review. Surv Ophthalmol. 2007;52(4):397-421. 2. Suh MH, Seo JM, Park KH, et al. Associations between macular findings by optical coherence tomography and visual outcomes after epiretinal membrane removal. Am J Ophthalmol. 2009;147(3):473-80. 3. Le Rouic JF, Becquet F, Ducournau D. Does 23-gauge sutureless vitrectomy modify the risk of postoperative retinal detachment after macular surgery? A comparison with 20-gauge vitrectomy. Retina. 2011;31(5):902-8. 4. Arias L, Monés J. Transconjunctival sutureless vitrectomy with tissue plasminogen activator, gas and intravitreal bevacizumab in the management of predominantly hemorrhagic age-related macular degeneration. Clin Ophthalmol. 2010;18:67-72. 5. Thompson JT, Sjaarda RN. Vitrectomy for the treatment of submacular hemorrhages from macular degeneration: a comparison of submacular hemorrhage/membrane removal and submacular tissue plasminogen activator-assisted pneumatic displacement. Trans Am Ophthalmol Soc. 2005;103:98-107. 6. García-Arumí J, Castillo P, López M, et al. Removal of retained subretinal perfluorocarbon liquid. Br J Ophthalmol. 2008;92(12):1693-4.

Chapter 14

Vitrectomy for Retinal Detachment with and without Proliferative Vitreoretinopathy J Fernando Arevalo, Reinaldo A Garcia, Veronica Oria

INTRODUCTION Repair of primary rhegmatogenous retinal detachment (RRD) was usually unsuccessful before Gonin1 demonstrated the importance of localizing and sealing retinal breaks. Scleral buckling introduced by Custodis,2 intraocular gases introduced by Norton,3 and the development of vitreous surgery by Machemer4 profoundly changed the history of RRD repair. Pars plana vitrectomy (PPV), a method originally reserved for complicated cases, is now used increasingly for primary repair of uncomplicated RRD.5 Vitrectomy may be selected to diminish complications associated with scleral buckling, to help relieve vitreoretinal traction and/or to create a large empty vitreous cavity in which a tamponade can be introduced. Even though vitrectomy is the most invasive of all techniques described for RRD repair, primary vitrectomy seems to be useful in complicated cases, which has an unfavorable prognosis with simpler procedures.6 The selection of alternative techniques for different types of retinal detachment (RD) is a matter of surgeon preference. However, a variety of relatively complicated RRD are currently best managed with vitrectomy techniques with or without associated scleral buckling: (a) RRD with proliferative vitreoretinopathy (PVR), (b) RRD associated with giant retinal tears (GRTs), (c) RD associated with proliferative retinal vascular disease, (d) RRD due to posterior breaks, (e) RD associated with viral and other forms of retinitis, (f) RD associated with posterior vitreoretinal traction, and (g) RD associated with significant vitreous opacification.7 The objective of this chapter is to discuss the different vitrectomy techniques available to repair RD with and without PVR in a step-by-step approach.

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COMBINED VITRECTOMY AND SCLERAL BUCKLING Scleral Buckling Technique Preparation of the Surgical Field Under peribulbar anesthesia, a 360° conjunctival peritomy at the limbus is performed, this maneuver can be facilitated by spreading Wescott scissors beneath Tenon’s capsule just posterior to the limbus, thereby avoiding the fusion of conjunctiva and Tenon’s capsule at the limbus. Taking into account the considerable manipulation the conjunctiva undergoes during scleral buckling, two radial relaxing incisions should be made to prevent tearing of the conjunctiva (Fig. 1). After peritomy, the space between Tenon’s capsule and sclera is entered in the four quadrants between the rectus muscles with closed blunt scissors. Opening the scissors at each quadrant lyses the episcleral fascial connections between Tenon’s capsule and sclera. The insertion of each rectus muscle is then engaged with a muscle hook. Once the muscle insertion is engaged, the connections to Tenon’s capsule can be identified and separated from the muscle. The septum is then cut between the forceps and the tip of the muscle hook with the scissors. This maneuver will expose the tip of the muscle hook from behind the muscle and septum. It is then verified that the entire muscle is engaged on the muscle hook (Fig. 2A). To expose the posterior part of the eye, the conjunctiva and Tenon’s capsule is pushed back with a cotton tip applicator (Fig. 2B). After isolation of the muscle is complete, a traction suture is placed around the muscle using either a fenestrated muscle hook or a reversed needle (Figs 3A and B); 2-0 or 4-0 black silk is an effective traction suture. All four rectus muscles can be isolated in this manner.8

Figure 1  (Arevalo et al) Limbal peritomy and relaxing incisions. Limbal peritomy is begun by grasping both Tenon’s capsule and the conjunctiva as close to the limbus as possible. A radial relaxing incision approximately 8 mm long is made through the conjunctiva and Tenon‘s capsule in oblique meridians to prevent tearing of the conjunctiva during exposure of the globe

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A

B

Figures 2A and B  (Arevalo et al) Isolation of muscle’s tendons. (A) The insertion of the rectus muscles is isolated using a muscle hook; (B) Tenon’s capsule and conjunctiva are retracted

A

B

Figures 3A and B  (Arevalo et al) Muscle engaging. (A) With the first muscle hook in place, a needle of a 4-0 black silk suture is passed through the holder’s tip of the second hook, and then it is passed under the muscle; (B) With the second hook in place, the first hook is retracted to engage one arm of the black silk suture. This procedure is repeated at the four rectus’ muscles

Accurate Placement of the Buckle on the Sclera This is one of the most important steps in the procedure. After ophthalmoscopic localization of retinal breaks, the surgeon should make temporary marks on the sclera with a scleral marker such as an O’Connor’s or Gass’ marker. The scleral mark is then enhanced with a sterile pen, superficial cautery or both (Fig. 4). For small flap tears or atrophic holes, a single mark on the posterior edge of the break is sufficient. Some surgeons prefer a single mark after a scleral burn with diathermy placed in the center of their anterior edge because the anterior edge is the usual site of persistent vitreoretinal traction. In lattice degeneration, both

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Figrue 4  (Arevalo et al) Localizing the retinal breaks. The black dots show the proper location of the external scleral marks, which are made to denote the boundaries of each break through indirect ophthalmoscopic visualization

ends of the degeneration are marked on the sclera. The boundaries of a dialysis are noted by marking both ends and the posterior extent to which the retina will likely fall. In large horseshoe tears, the posterior edge and the ends of the anterior flaps are marked externally on the sclera. Both anterior and posterior extent of the tear is important to note because not all the time the horseshoe tear is radially oriented.6 If the retina is bullously detached, elevated breaks appear to lie more posteriorly than their true location because of parallax.8 Rarely it may be necessary to drain subretinal fluid to flatten the retina before localization. If no specific pathologic factor is to be supported, the encircling element should support the posterior margin of the vitreous base.

Encircling Exoplants Although radial exoplants are preferred with large horseshoe tears and relatively posterior tears without the presence of other retinal pathology, specifically other areas of vitreoretinal traction away from the segmental element are not supported, which may result in formation of new retinal breaks. Traditionally an encircling exoplant is chosen for RD with multiple breaks, aphakic or pseudophakic eyes, high myopia, extensive areas of lattice degeneration, PVR grade B or greater, giant tears, and eyes with very thin sclera.8 We prefer an encircling #41 silicone band alone or a #240 silicone band alone or with a piece of grooved soft silicone tire (#506 gauge) placed beneath the encircling band in areas needing support of retinal breaks or vitreoretinal traction. The addition of the encircling band ensures a permanent buckling effect and provides some degree of support in areas where it is necessary, even though it is not intended to be of a significant height. The band is passed around the circumference of the globe and beneath the rectus muscles (Fig. 5), and then it is anchored with

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Figure 5  (Arevalo et al) Encircling procedure. An encircling #240 solid silicone band is passed under the four rectus muscles. If there are small tears, the band is positioned just over them. In large posterior horseshoe tears, the band can be combined with a grooved 5 mm sponge (#506 gauge). When there are no pathologic areas, the encircling exoplants can be fixed 12 mm posterior to the limbus. The two ends of the band are joined together by pulling in opposite direction through a silicone slip (#70)

a single mattress suture with posterior bites located 12 mm away and parallel to the limbus placed at the center of each quadrant (Fig. 6). When a piece of grooved silicone tire is added beneath an encircling band, suture bites are always placed posterior to the location overlying the responsible retinal break(s).

Figure 6  (Arevalo et al) After the ends of the encircling element have been trimmed, it is anchored in each quadrant along the greatest circumference of the globe using a 5-0 nonabsorbable suture (such as polyester, nylon or polypropylene) with a spatulated needle

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SCLERAL SUTURE TECHNIQUE A spatulated needle with a 5-0 nonabsorbable suture such as polyester, nylon or polypropylene is used. When suturing, the surgeon must firmly fixate the globe by grasping a muscle insertion with a toothed forceps. The suture is passed through the sclera at one-half to three-fourths depth over a distance of 3–5 mm, usually in a horizontal mattress fashion. The #240 encircling band is sutured with the posterior border 12 mm posterior to the limbus (Fig. 6). The #41 encircling band is sutured at the vitreous base just posterior to the rectus muscle insertions. Usually sutures are placed a minimum of 2 mm farther apart than the width of scleral contact for a given silicone element. To ensure that the most posterior edge of the retinal break is supported, the surgeon places the posterior suture a minimum of a 2–3 mm posterior to the scleral localization mark.8 The ends of the band should be secured with a silicone sleeve (#70) because it allows easy adjustment of the band throughout surgery.

PRIMARY VITRECTOMY As we usually combine vitrectomy with an encircling scleral buckling, a 360° peritomy with isolation of the rectus muscles has to be done. Light bipolar diathermy is applied to the episcleral vessels in preparation for sclerotomies. Sclerotomies are made 2.5–3 mm posterior to the limbus in pseudophakic or aphakic eyes or in eyes in which a lensectomy is planned. Sclerotomies are made 3.5–4 mm posterior to the limbus in phakic eyes. The sclerotomy sites must be placed more anteriorly in infant eyes and in eyes in which the retina is pulled anteriorly over the pars plana by anterior fibrous traction (e.g. PVR). The infusion port should be located just inferior to the meridian of the lateral rectus insertion, while the instrument sclerotomies should be just superior to the meridians of the horizontal rectus insertions.9 The sclerotomies are made with a microvitreoretinal (MVR) blade with the flat portion parallel to the limbus. The knife is directed toward the center of the phakic eye, though it can be directed slightly more anteriorly in the aphakic eye (Fig. 7). The clamped infusion cannula is then placed into the vitreous cavity through the inferotemporal sclerotomy. Its position in the vitreous cavity is ascertained by directly visualizing the cannula before being opened for infusion. The nasal sclerotomy for the fiber optic light source is usually made next (Fig. 8). The sclerotomy is made with a 20-gauge MVR blade, and then the light probe is placed into the eye. With the eye stabilized by the nasal instrument, a temporal sclerotomy is made, and the vitrectomy instrument is placed in the eye and the infusion is turned on.

Basic Operative Steps in Primary Vitrectomy Although not all must be met in every case, there are seven goals of primary vitreous surgery: 10

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Figure 7  (Arevalo et al) Placement of the irrigation port. Previous to anchoring the infusion cannula at the inferotemporal quadrant, a deep and short 6-0 vicryl suture bite parallel to the surface of the sclera and in opposite directions is passed around the sclerotomy measured point. The MVR knife is carefully passed through the pars plana at 2.5 mm posterior to the limbus in aphakic or pseudophakic eyes, and at 3.5 mm in phakic eyes

Figure 8  (Arevalo et al) One suture loop is placed on the shoulder of the cannula while the opposite loop is pulled up. Then the other loop is tied with a slip knot over the opposite shoulder. The infusion line is opened (after tip visualization) and finally the other two sclerotomies are made in the superior quadrants

1. Removal of vitreous opacities preventing adequate visualization: After making sure that the infusion is on, cutting is tested in the central anterior vitreous. Moderate suction usually between 100 mm Hg and 250 mm Hg and a rapid cutting rate of 1,000–2,500 cycles/second are generally used.

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279 New vitrectomy systems allow for a cutting rate of 5,000 cycles/second. The procedure should begin in the anterior one-third of the vitreous, in an area in which visualization is relatively good and away from the lens. As visualization improves and the anterior vitreous is removed, the vitrectomy probe may be moved more posteriorly in the eye to clear the media (Fig. 9). If the posterior hyaloid is collapsed and thin, it may curl around the vitrectomy instrument tip into the cutting port even if the port is not directed toward the hyaloid. If the hyaloid is thickened, it is necessary to direct the port toward the hyaloid (see removal of posterior cortical vitreous). The hyaloid is engaged and cut in a centrifugal manner, enlarging the opening in progressively larger concentric circles toward the periphery. In most instances, it is only necessary to excise enough vitreous to enable an adequate view of the peripheral retina. It is usually not necessary to depress the vitreous in the uncomplicated case. If a peripheral retinal break is present or suspected or if focal peripheral vitreoretinal adhesions are present, it is necessary to remove peripheral vitreous more completely (Fig. 10). 2. Removal of perpendicular traction: Vitrectomy is begun, as described earlier, to remove the anterior and middle gel of the vitreous cavity. The goal here is to remove perpendicular traction forces leading to open breaks, particularly in RD associated with posterior breaks or in tractional RDs associated with vitreomacular traction or diabetic retinopathy. In cases with a posterior cortical vitreous partially detached, a vitrectomy can be performed in 360° to relieve perpendicular traction that keeps the retinal break(s) open. In diabetic patients where fibrous proliferation can grow onto the surface of the posterior cortical vitreous, an en bloc or a modified en bloc approach can be utilized. Vitreomacular traction can be divided into tangential, anteroposterior and combined traction. Anteroposterior traction

Figure 9  (Arevalo et al) Once a central cavity has been created in the opaque vitreous, visibility may improve so that vitrectomy of retrolental opacities can be done more safely. As soon as the retrolental region has been cleared of opacities, removal of opaque vitreous proceeds posteriorly

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Figure 10  (Arevalo et al) When vitrectomy is directed to the vitreous base, the assistant applies a scleral depressor or a cotton swab in the area of the opaque vitreous base, pushing it toward the axial region and making it more safely accessible to vitrectomy. The cutting frequency of the probe is increased, and suction is set at a low level to minimize traction to the peripheral retina

is released with careful “core” vitrectomy. If vitreous is firmly adherent only to the macula or if there is traction over the macula, it is advisable to cut these adhesions with scissors before the vitrectomy is completed to reduce the risk of creating an intraoperative macular hole (MH). 3. Removal of posterior cortical vitreous (tangential traction): Tangential traction may arise from the posterior cortical vitreous layer as well as from underlying preretinal membranes or the internal limiting membrane (ILM). After removal of the central vitreous, the posterior cortical vitreous must be identified and separated from the retinal surface. The posterior cortical vitreous is most easily identified with the use of a soft-tipped silicone suction cannula. When active suction is lightly applied, the orifice of the cannula becomes occluded by the cortical vitreous, and as the cannula is swept close to the retinal surface, the cannula flexes. Because of the analogous movement, this has been called the “fish strike” sign11 or the “diving rod” sign.12 The cortical vitreous is then separated from the inner retinal surface, creating a posterior vitreous detachment (PVD). This is performed by engaging the cortical vitreous in the area adjacent to the optic disk with the suction/cutting instrument or cannula using active suction (100–300 mm Hg) and elevating it in a posteroanterior direction. With the creation of a PVD, the surgeon usually can visualize a floating Weiss’ ring. Once detached to the equator or just posterior to it, the infusion bottle is elevated and the suction function of the vitrectomy probe is switched to cutting and aspiration to remove the vitreous layer. Generally, the cortical vitreous only needs to be removed from the posterior pole and arcades or from the area of interest. 4. Membrane surgery approach: Membrane peeling: If an edge of the membrane is not apparent, then a pick or a bent 20-gauge needle, or a bent

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281 MVR blade, or a diamond-dusted silicone tipped cannula (Tano’s scraper) can be used to create an edge. When a well-defined edge of a preretinal membrane can be visualized, the edge of the membrane is explored with a membrane pick, until the edge is elevated; it is usually then possible to grasp it with a membrane forceps. This tissue is then gently stripped away from the retina. If the membrane is tightly adherent to the retina, regrasping the membrane and gently stripping from several points will help in membrane removal. These multiple “regraspings” should take place as close to the membrane-retina interface as possible. Sometimes a surgeon notes that the retina is becoming elevated away from the retinal pigment epithelium (RPE). At this point, the membrane should be re-engaged at another site and a different directional vector force used to strip the membrane. If the retina is pulled up and the membrane cannot be removed, then the membrane can sometimes be truncated with horizontal scissors to relieve traction or cut it from its adherence to the retina.   Membrane sectioning: The membranes are often widespread and involve the posterior cortical vitreous. The vitreous and membranes may or may not be separated from the retina surrounding the epicenters. Sectioning the membranes between the epicenters will often adequately relieve traction. The area of the vascular epicenters is identified, and the distal blade of the vertically cutting scissors is placed into the space between the membrane and the underlying retina between the adjacent epicenters. At this point the membrane is cut to relieve tangential traction. If the vitreous is not separated surrounding the epicenters, it is necessary to lift the posterior hyaloid with the tip of the scissors or a membrane pick to separate the hyaloid from the retina, so the scissors can enter the space between the retina and the membrane prior to cutting. If the membrane is vascularized, it may be advantageous to apply endodiathermy to large vessels prior to cutting and to residual bleeding vessels after the cut.9   Membrane delamination: Vascular membranes can be removed from the retina by dissecting the membrane free at the vascular epicenters. First, the vitreous near the membrane is excised, then the membrane is lifted unimanually with the scissors or bimanually with an illuminated pick. The membrane is lifted with closed scissors to separate attachments to the retina surrounding the epicenter, and then the epicenter is cut parallel and flushed with the retina to separate the membrane. After all the vascular epicenters are dissected free from the retina, the membranes and vitreous are removed with the vitreous cutter.9 5. Flattening the retina with perfluorocarbon fluid-air exchange/perfluorocarbonair exchange: Perfluorocarbon liquid: Perfluorocarbon liquids (PFCL) can help identify the location of occult break(s) by exerting a posterior flattening force that displaces the subretinal fluid through the peripheral break; exhibiting “Schlieren”, seen when two liquids of differing refractive index are mixed. The retinal break(s) can be located by observing the direction

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282 of Schlieren flow. Perfluorocarbon liquids can also reveal areas of the retina previously obscured by a bullous detachment, potentially exposing occult retinal breaks. Once the retinal break(s) have been identified, PFCL is added until the bubble meniscus is located at the posterior edge of the most anterior retinal break. Laser endophotocoagulation can be applied to posterior breaks at this time or deferred until after the fluid-air exchange. A PFCL/air exchange is then performed with drainage of sub-retinal fluid to the most anterior break. Perfluorocarbon liquid is then removed at the anterior interface. Once all PFCL has been removed, further endophotocoagulation to the peripheral anterior break(s) is applied, and an appropriate intraocular gas tamponade is exchanged for air.   Fluid or perfluorocarbon-air exchange: Once the vitreous has been removed, the break has been identified, and preretinal membranes have been stripped; a fluid-air exchange or perfluorocarbon (PFC)-air exchange is performed to flatten the retina, fill the eye with air and, provide internal tamponade of a retinal break. It may be also performed to remove subretinal fluid. During fluid-air exchange or PFC-air exchange subretinal fluid can be drained through a posterior break. Depending on case severity, air is then exchanged for a long-acting gas or silicone oil.   With the air pump pressure to approximately 35–45 mm Hg, we turn on the air, which is insufflated through the infusion port. The stopcock is turned “on” to air and “off” to infusion. Air is insufflated to replace the volume of fluid removed. As the air enters the eye the fluid is removed from the anterior vitreous cavity with a back-flush needle held over the retinal break to aspirate subretinal fluid. Sometimes air over the break may limit aspiration of viscous subretinal fluid. Therefore, it is helpful to begin aspirating the subretinal fluid before the air seals the break opening. Subretinal fluid appears as a viscous stream compared with balanced salt solution within the vitreous cavity. We then remove progressively more posterior fluid until all the fluid or PFCL is removed. The posterior meniscus of the fluid and PFCL is easily identified by observing the light reflex at its surface. The light reflex that is prominently seen tends to dull or disappear as the needle tip touches the posterior meniscus. Once the posterior fluid or PFCL is entered with the needle tip, the needle is held in place and suction is applied. When the fluid level passes below the needle tip, the light reflex from the meniscus reappears once more. This technique is continued over the optic nerve until all the fluid is gone. If the retina is still detached and no posterior retinal break is present, a posterior drainage retinotomy using endodiathermy can be created, usually in the superonasal quadrant, one and half disk diameters from the optic disk.9 After initial fluid-air exchange, sequestered intraocular fluid from the anterior walls of the eye can be removed from the posterior pole with the back-flush needle after waiting for 1 minute. 6. Tamponade with gas or silicone oil: Air-gas exchange: In order to prevent the expanding gas bubble from increasing the intraocular pressure (IOP), it

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283 is safer to instill a nonexpansile concentration of gas. Mixtures of 20% SF6 with 80% air and 14% C3F8 with 86% air are clinically nonexpansile.9 Pure gas is mixed with air to the desired concentration in a 60 ml syringe. The ports are sutured first. The gas mixture then is injected by the assistant through the infusion cannula while the surgeon holds a 30 gauge syringe without its plunger, and connected to a needle in the vitreous cavity. The surgeon monitors IOP tactilely and notes as the gas mixture is injected into the vitreous cavity, replacing the air. We usually flush with 60 ml or more of the gas mixture. Gas should be injected through a millipore filter to ensure sterility.   Air-silicone oil exchange: If silicone oil is used, it is injected slowly into the vitreous cavity through a short, large-bore needle. Air escaping from the sclerotomies prevents IOP from rising too high during this maneuver. Air infusion pressure can also be progressively reduced or the tubing clamped. A small inferior iridectomy should be performed in aphakic or pseudophakic eyes with a ruptured posterior capsule to permit aqueous flow into the anterior chamber postoperatively to maintain an open angle and silicone oil behind the iris. 7. Creating chorioretinal adhesion with endolaser: Low power and long duration (0.2–0.5 seconds) applications are used when treating with endophotocoagulation. Short duration burns of higher power increase the risk of rupturing Bruch’s membrane. Endolaser energy is delivered under fluid, air, PFCL (our preferred method) or silicone oil. The laser probe is held near the retina until the aiming beam is clearly seen, and then laser is applied. The power is increased and/or the probe is held closer to the retina until there is whitening (coagulation) of the tissue. Higher power is necessary if there is reduced pigmentation of the fundus or if there is residual subretinal fluid; conversely less power is necessary in the presence of a darkly pigmented fundus and attached retina.9

INTRAOCULAR TAMPONADE For the forms of RD surgery requiring vitreous surgery, sulfur hexafluoride (SF6) and perfluoropropane (C3F8) gases are used more frequently to provide extended internal tamponade. In GRTs or highly myopic eyes with RD from MH, a large volume of gas is desirable until the chorioretinal adhesion resulting from photocoagulation or cryotherapy is established. Perfluoropropane is a good choice selection for these conditions (for silicone tamponade see internal tamponade in PVR).13

SMALL-GAUGE PARS PLANA VITRECTOMY Small-gauge vitrectomy (25-gauge and 23-gauge) is becoming increasingly popular and is replacing standard 20-gauge vitrectomy for many surgical indications. According to the Preferences and Trends survey conducted of

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284 its memberships annually by the American Society of Retina Specialist, 48% of respondents in 2004 had never tried small-gauge PPV; by 2007, 80% of respondents used it for most of their cases.14 Small-gauge vitrectomy systems have become available from multiple manufacturers, and many vitreoretinal surgeons have begun transition to small-gauge vitrectomy based on the theoretical advantages of small-gauge PPV including reduction in inflammation, patient discomfort, recovery time, surgery induced astigmatism and changes in corneal topography and for some cases, operative time. However, because of the increased flexibility associated with the smaller instrumentation, surgical indications most conducive to small-gauge PPV initially were limited to those not requiring extensive vitrectomy or membrane dissection. Over the last few years, advances in technology and instrumentation, such as the development of second generation small-gauge instruments, ultra high cutting machines, and brighter xenon light sources; modifications in surgical technique, and surgeons’ increasing confidence and experience with the system have promoted an expansion of surgical indications including primary RD and even to complicated cases, such as recurrent RD, complicated RDs, tractional RDs in patients suffering from proliferative diabetic retinopathy (PDR), PVR, neovascular glaucoma, GRTs, pathologic myopia and cases in which silicone oil injection is obligatory. The choice of instrument gauge is definitively evolving, as surgeons decide according to their personal experience and expertise which cases are preferable for small-gauge vitrectomy versus the ones performed more easily with 20-gauge instrumentation.15-18

Sclerotomies with 23-Gauge Vitrectomy The conjunctiva is displaced using a cotton tip applicator, forceps or pressure plates, taking care not to tear it. In general the more oblique (longer) the path through the sclera, the better the edges reappose when the cannulas are removed. However, endoscopic evaluations of the sclerotomies have shown vitreous plugging the wounds in both 23 and 25 gauge cases.19 Therefore, the majority of surgeons favor a biplanar scleral incision, with a more oblique initial and more perpendicular final entry into the vitreous to create a two-step incision in cross section (Fig. 11), although this is difficult to achieve consistently. Ultrasound biomicroscopy has not shown any statistical difference in wound size between a single plane and 23-gauge biplanar incisions.20

Sclerotomies with 25-Gauge Vitrectomy In the original 25-gauge vitrectomy, after the displacement of the conjunctiva, trocars were placed perpendicular to the sclera (similar to 20-gauge technique), but many surgeons now advocate oblique incisions to promote watertight wound closure. It has been postulated that oblique sclerotomies may become lax and deformed because of pivoting motions of the instruments during

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Figure 11  (Arevalo et al) Schematic surgical steps for oblique 23-gauge sclerotomy. After conjunctival displacement, the eyes are penetrated as tangentially as possible (10–30°) parallel to the corneal limbus with the bevel up; once past the trocar sleeve, the angle is changed to 90° (perpendicular to surface)

peripheral vitrectomy. The degree of scleral rigidity also may play a role, because the more flexible sclera in younger patients may result in incomplete closure of the sclerotomy sites. Trocar wound construction may be important for avoiding gas leakage in some cases. Although, a possible mechanism for 25-gauge wound closure is the plug created by vitreous incarceration into the scleral wound,21,22 in most RRD cases, meticulous anterior vitreous removal is necessary. Therefore, a well-constructed oblique sclerotomy may leak because of a lack of vitreous prolapse. In addition, the increased flexibility of the smaller 25-gauge instruments limits the ability to use long, oblique incisions due to deformation of the shaft when the oblique entry is brought into the perpendicular position that is most convenient when performing the vitrectomy.

NEW CONSIDERATIONS IN FLUID DYNAMICS DURING SMALL-GAUGE VITRECTOMY The evolution of smaller cutters was accompanied by a number of drawbacks, one of which was the occurrence of a decrease in flow rate that can take place during the vitrectomy, a fact that can lead to undesirable extension of operation time. The flow rate through the cutter is influenced by several factors, such as the diameter of the cutter’s opening, the duty cycle, the vacuum strength, the viscosity of the aspirated vitreous, the mechanism upon which the cutter is based (pneumatic or electrical), the movement of the blade and the internal diameter of the cutter’s lumen.23 According to Poiseuille’s equation, flow is related to the fourth power of the internal diameter of the vitrectomy probe and is inversely related to the length of the 25-gauge vitrector and associated tubing. This explains the marked and moderated decrease in flow with 25 and 23-gauge probes respectively compared to 20-gauge. Most 20-gauge vitrectomy

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286 are performed at IOPs between 30 mm Hg and 40 mm Hg, vitrectomy with 23-gauge instrumentation can be performed at these infusion pressures, but 25-gauge vitrectomy is more efficient at higher infusion pressures, in the range of 40–50 mm Hg, because of the smaller diameter of the instrument. Increasing the infusion pressure improves flow to make the vitreous removal somewhat faster than, but still not as rapid as with a 20-gauge system. The aspiration pressure is another factor that influences how long it takes to remove the vitreous. Small-gauge vitrectomy instruments require higher aspiration pressures to achieve a reasonable rate of vitreous removal. The maximun suction setting is typically about 150 mm Hg for 20-gauge vitrectomy, 400 mm Hg for 23-gauge, and 600 mm Hg for 25-gauge. Finally the duty cycle (the length of time the vitrector port is open compared to the time it is closed) results in higher flow rates, and this can partially compensate for the decreased flow inherent in smaller diameter 23 and 25-gauge instruments. The commercially available small-gauge vitrectomy machines differ in their abilities to control duty cycles.24

Increasing Safety In vitreoretinal surgery safety often depends on two main factors: fluidics stability and tissue separation. Fluidics stability and the risk of vitreous traction depend on the flow rate, lumen area and cut rate. If the flow rate is increased, the length of pull of collagen fibril is increased so, vitreous traction is increased, decreasing safety. Conversely, increasing the cut rate decreases the length of pull of collagen fibril, decreasing vitreous traction, and increasing safety. So, maximum safety requires low flow with ultra-high cutting. At a fixed distance, the amount of flow required for tissue attraction is less for the 25-gauge probe than both 23 and 20-gauge. Then, the chance of inadvertently incarcerating the normal retina would be lower with smaller gauge. Duty cycle in new vitrectomy systems allows the surgeon to switch the duty cycle to “shave” in which the cutter is closed the majority of the time, reducing the risk of retinal incarceration. In addition, then surgeons do not need for instrument exchange as often as the cutter acts as vertical scissors. Finally new technology has created new vitrectors with the probe opening closer to tip that allow surgeons to remove scar tissue in more proximity to the retina without touching it with the probe.

Wound Closure In order to decrease the vitreous plugging in the wounds some surgeons suggest removing firstly the trocars over the cannulas to finally remove the cannulas (Fig. 12). Cannulas should be removed at roughly the same flat angle of insertion and the sclerotomy tunnel compressed with a cotton tip swab to collapse and close the tunnel. We usually increase the IOP to 60 mm Hg, while compressing the sclerotomy tunnel with a cotton tip swab, when an immediate sclerotomy leak does not cease with cotton tip swab compression

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Figure 12  (Arevalo et al.) Removing first the trocars over the cannulas to finally remove the cannulas (A), Cannulas should be removed at roughly the same flat angle of insertion, (B) The sclerotomy tunnel compressed with a cotton tip swab to collapse and close the tunnel (C)

alone. However, if the surgeon is unsure if the wound is leaking or not, then it is probably best to suture. In cases with gas tamponade, suturing of sclerotomies in leaking trocar insertion sites should be performed based on the presence of subconjunctival gas bubbles associated with hypotony during sequential trocar extraction. After scleral suturing, additional nonexpansible gas mixture should be injected into the vitreous cavity through the maintainer port, or through the sclera with a 30-gauge needle when leakage is evident from the last removed trocar entry wound. More common complications associated with the small-gauge PPV:

Retinal Tears It is generally agreed that less peripheral vitreous is removed during a standard small-gauge vitrectomy than during a standard 20-gauge vitrectomy. Thus, a theoretical concern exists that contraction of this more prominent residual vitreous skirt could cause significant anterior vitreoretinal traction and subsequent retinal tears. The rate of retinal tears discovered during surgery for MH and epiretinal membrane has been reported to be between 0% and 24%, with most series reporting an incidence of less than 5%.25 In the largest retrospective series of 177 consecutive 25-gauge PPV cases, the incidence of intraoperative retinal breaks was 15.8%, with roughly two-thirds of these occurring away from the superior sclerotomies.26 According to recent reports the rates of iatrogenic retinal breaks in small-gauge vitrectomy are comparable (if not smaller) to previously published series of modern 20-gauge surgery. Furthermore, in one comparative series of 25-gauge and 20-gauge cases, no

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288 statistically significant difference in the incidence of intraoperative retinal breaks was found (3.1% of the 25-gauge cases compared with 6.4% of the 20-gauge cases).27

Hypotony There are numerous reports of hypotony following sutureless small-gauge vitrectomy. The hypotony is usually transient, lasts up to a few days following surgery, and improves spontaneously once the sclerotomies heal adequately. Localized choroidal detachments were found in 69% of eyes using anterior segment optical coherence tomography in one study.28 In some eyes the hypotony can be more severe, causing large choroidal detachments or escape of gas with inadequate tamponade in eyes with retinal breaks or detachments. Improved trocar/cannula placement using beveled rather than perpendicular incisions and treatment of any leaking sclerotomies at the end of the case have decreased, but not eliminated this complication.24

Endophthalmitis Intraocular infection is another complication that was initially suspected to occur more frequently after sutureless vitrectomies. The explanation for the increased incidence of endophthalmitis following sutureless vitrectomy was that bacteria on the ocular surface entered the eye through defects in the conjunctiva and sclera, then some surgeons advocated aggressive removal of the vitreous around the cannulas to prevent vitreous prolapse into the wounds. However, the currently available data from the recently published large retrospective studies does not indicate that sutureless small-gauge vitrectomy is associated with higher rates of endophthalmitis than in 20-gauge vitrectomy. Noteworthy, the surgeons in those studies used an oblique penetrating angle to the eye wall.29-31

VITRECTOMY FOR RETINAL DETACHMENT WITH PROLIFERATIVE VITREORETINOPATHY Proliferative vitreoretinopathy is an intraocular wound healing disorder characterized by a breakdown of the blood-retinal barrier, proliferation of RPE cells, glial cells, inflammatory cells, and extracellular matrix production on the retinal surface, subretinal space, and in the vitreous cavity, that lead to the formation of subretinal and epiretinal membranes. The cell mediated contraction of these membranes causes tangential retinal traction and fixed retinal folds.32,33 The cells in the vitreous are often seen by slit-lamp examination and appear as pigmented dots. The cells on the surface of the retina usually go unrecognized until the retina detaches; even then, the fixed folds resulting from cellular traction, rather than the cells themselves, are most often seen. Initially the detachment may be purely tractional, but almost always the traction results

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289 in reopening of a pre-existent break(s) or occurrence of new breaks, causing combined tractional-rhegmatogenous RD.33 Proliferative vitreoretinopathy most frequently develops in the inferior retina or is at least most severe in the inferior retina. The predisposition for the inferior retina is believed to be the result of gravity, whereby the RPE and inflammatory cells liberated into the vitreous cavity via retinal tears settle in the inferior vitreous.34

RISK FACTORS FOR THE DEVELOPMENT OF PROLIFERATIVE VITREORETINOPATHY Because it is now possible to treat subjects at high risk for developing PVR, it is important to identify and target those subjects to avoid costly and complex vitreoretinal surgery. In addition, to improve the prognosis of RD surgery recent research has focused on the use of intravitreal pharmacological agents to prevent the occurrence of PVR, although none of these agents is used routinely in clinical practice owing to concerns about retinal toxicity. However, if risk factors for the development of PVR could be identified, these potentially toxic intravitreal treatments could only be targeted at those patients at greatest risk.35 Many studies have investigated and identified a number of clinical risk factors for PVR including (a) Long RD duration; with long duration defined as greater than 3 months.36 Tseng et al32 have hypothesized that the long detachment duration allows more time for RPE cells to be in contact with vitreous to migrate, proliferate, and produce extracellular matrix, ultimately causing contraction of epiand subretinal membranes, fixed retinal folds, and retinal traction, (b) Eyes with large retinal breaks; RDs larger than two quadrants or GRTs at increased risk of developing PVR,37 with large retinal breaks more cells can be induced to migrate and proliferate and thereby contribute to the woundhealing response characteristic of PVR,1 (c) Horseshoe tears;32,37,38 a lower rate of PVR among eyes with atrophic holes compared with those with horseshoe tears has been previously reported.38 Tseng et al32 speculated that traction exerted on the hole margin in eyes with horseshoe tears may allow greater vitreous fluid movement through the hole to contact RPE cells, (d) Vitreous hemorrhage;32,37 it is likely that serum released into the vitreous as a component of vitreous hemorrhage may further elevate the vitreous serum concentration above that induced by blood-ocular barrier breakdown alone,32 (e) Patients with uveitis or increased inflammation from trauma are at increased risk for PVR, especially if the eye has a retinal break,39 (f) Prior RD repair is the most common factor that predisposes an eye to PVR, although some of these eyes may have developed PVR regardless of the technique used for repair of the initial RRD. The RD surgery itself appears to hasten PVR in eyes predisposed to this problem by releasing proliferating cells into the vitreous and causing breakdown of the blood-ocular barrier, which creates an environment promoting cellular proliferation,40 (g) Excessive

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290 cryopexy releases viable RPE cells and creates breakdown of the bloodocular barrier, which creates an environment conductive to the development of PVR.41 Laser appears to cause less breakdown of the blood-ocular barrier than cryopexy,42 (h) Postoperative choroidal detachment; may predispose eyes to develop PVR,43 (i) The existence of preoperative PVR suggests that the cellular, extracellular, and chemical elements required for wound healing are present. It is therefore not unreasonable to expect preoperative PVR to be a risk factor for the development of postoperative PVR. Girard et al.43 in a retrospective study of preoperative PVR grades B and C1 found only grade B but not grade C1 preoperative PVR to be a significant risk factor. They concluded that grade B PVR might represent an immature form of PVR with a definitive potential for progression, whereas grade C1 PVR may represent a spontaneously arrested, nonevolutive form of the disease. However, other studies have found grade C PVR to be a significant risk factor,35 (j) Although controversial, the pathological mechanism by which aphakia could be related to the development of PVR is unclear. However the breakdown of blood-ocular barrier may be significant.37 Miyake et al44 suggested that the posterior lens capsule might protect the anterior uvea (site of active transport) from mechanical and physical irritation by vitreous gel. It is also possible that the intact lens provides a physical barrier for transmission of inflammatory cytokines from the anterior chamber to the vitreous cavity. The disruption of blood-retinal barrier would, in theory, allow serum factors such as fibronectin, to enter and remain in the vitreous and may enhance the development of PVR. Asaria et al45 determined prospectively the accuracy of a predictive risk formula for the development of postoperative PVR when applied in a clinical setting; this prospective study has shown that with the use of a clinical risk formula it is possible to identify individuals at greater risk for PVR after primary vitrectomy.

DIAGNOSIS OF PROLIFERATIVE VITREORETINOPATHY Epiretinal proliferation causing traction on the retina in an eye with a RRD is the most common presentation of PVR.41 The finding of a triangular RD by B-scan ultrasonography and retinal stiffness on kinetic ultrasonography in eyes with opaque media is diagnostic of advanced PVR. The ultrasonographic triangular configuration is created by a proliferative membrane that attach detached retina anteriorly.46

CLASSIFICATION OF PROLIFERATIVE VITREORETINOPATHY In the past 30 years the classification of PVR has evolved as a result of increased understanding of the pathophysiologic processes in this disorder. The most popular and universal classification system is the updated version of the Retina

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291 Society classification. This refined classification system by Machemer and coauthors was an improvement over the original classification, since it provides more detailed information about the location, extent, and severity of PVR in an individual eye.47 This system divides PVR into three major grades: Grade A, vitreous haze, vitreous pigment clumps and pigment clusters on inferior retina (Fig. 13); Grade B, wrinkling of inner retinal surface, retinal stiffness, vessel tortuosity, rolled and irregular edge of retinal break(s) and decrease mobility of vitreous (Fig. 14); and Grade C, focal, diffuse or circumferential full-thickness folds and/or subretinal strands and/or anterior displacement and condensed vitreous strands. It is important to note how many hours of the clock are affected by PVR and their anteroposterior localization, Grade CA 1–12 or Grade CP 1–12 respectively. Finally they subclassified PVR grade C into five subcategories:

Type 1 Focal contraction: Is caused by an epicenter or multiple isolated epicenters of contraction in the posterior zone of the retina. Because there is a focal point toward which the resulting traction is directed, folds radiate away from each epicenter in a characteristic starfold configuration (Fig. 15).

Figure 13  (Arevalo et al) Proliferative vitreoretinopathy Grade A represents the earliest recognizable manifestation of intraocular proliferation. It is characterized by uncomplicated rhegmatogenous retinal detachment (R), presence of pigment clumps (A) in the vitreous matrix, and decreased mobility of the posterior vitreous surface (P), retinal tear (T) Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

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Figure 14  (Arevalo et al) Proliferative vitreoretinopathy Grade B is defined by the presence of wrinkling of the inner retinal surface (W), retinal breaks with irregular edges (B), and tortuous retinal vessels (V) from not yet visible periretinal membranes. The retina frequently appears slightly rigid and the vitreous may have decreased mobility Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

Figure 15  (Arevalo et al) Proliferative vitreoretinopathy Grade C Type 1 has focal posterior contraction as a single star fold (S) or multiple isolated single star folds. This type only occur posterior to the posterior border of the vitreous base (B) Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

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Type 2 Diffuse contraction: Is caused by linked adjacent epicenters of contraction that produce a diffuse area of irregular retinal folds in the posterior portion of the retina. Contraction in an anterior-posterior direction tends to flatten the normally bullous contours of the more anterior retina. Contraction in the circumferential direction creates a funneled configuration of the posterior retina, with folds radiating anteriorly toward the ora (Fig. 16).

Type 3 Subretinal proliferation: It can appear as an annular fold of the retina in the area of the optic nerve and also manifest as a subretinal band which can be single or branching (Fig. 17).

Type 4 Circumferential contraction: Is caused by diffuse preretinal membrane contraction within or immediately behind the insertion of the posterior hyaloid, which produces an area of irregular folds in this region of the retina. The retina is contracted in a circumferential direction and therefore a series of radial folds tends to form in the redundant retina on either side of the area of irregular folds that extend posteriorly (Fig. 18).

Figure 16  (Arevalo et al) Proliferative vitreoretinopathy Grade C Type 2 is a diffuse posterior contraction. It is marked by areas of irregular full-thickness retinal folding (F). This type only occur posterior to the posterior border of the vitreous base (B) Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

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Figure 17  (Arevalo et al) Proliferative vitreoretinopathy (PVR) Grade C Type 3 is basically PVR with subretinal proliferation. It can appear as an annular fold (A) of the retina in the area of the optic nerve. It may also manifest as a subretinal linear band (S), which can be single or branching. This type of contraction may be found anteriorly and posteriorly Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

Figure 18  (Arevalo et.) Proliferative vitreoretinopathy Grade C Type 4 is a circumferential contraction (C) along the posterior edge of the vitreous base (B) with central displacement of the retina (R). The peripheral retina is stretched and radial retinal folds (F) can be seen extending posteriorly from the posterior border of the vitreous base Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

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Type 5 Anterior displacement: Occurs most commonly in eyes that have either undergone a previous PPV or incurred penetrating trauma. Proliferative membranes, which are variably opacified, are present on the remnants of the posterior hyaloid, the anterior hyaloid, and the surface of the residual vitreous base. Their contraction at the vitreous base pull peripheral retina anteriorly to the pars plana, pars plicata, or even to the posterior iris. This may lead to anterior RD, or to ciliary body detachment and hypotony (Fig. 19). Most eyes requiring vitreoretinal surgery for this indication have PVR Grade C.

SURGERY FOR PROLIFERATIVE VITREORETINOPATHY Timing of Surgery The goal of surgery for PVR is to reattach the retina as soon as possible but to avoid recurrent RD resulting from reproliferation. In most eyes with PVR, the epiretinal proliferation becomes mature within 6–12 weeks of the onset of the disease. If the macula has previously been detached and there is little hope of achieving a visual acuity better than 20/200, it is often advisable to wait several

Figure 19  (Arevalo et al) Proliferative vitreoretinopathy Grade C Type 5 Contraction is an anterior displacement of the vitreous base (1-arrow). The posterior border of the vitreous base is pulled anteriorly by proliferative tissue (P) and attaches to the pars plicata of the ciliary body, posterior surface of the iris, or even to the pupillary margin. This creates a circumferential fold (F) of the retina with a trough (T) anterior to this fold Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

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296 weeks for the proliferation to mature, even though the macula remains detached for additional time. If the macula was never previously detached and it is still attached or has become detached within the past few days, then it is usually best to operate promptly to try to preserve macular function even though the risk of recurrent proliferation is greater.40

Scleral Buckling in Proliferative Vitreoretinopathy Although some authors48,49 have reported in PVR classified as grade C3 or worse that vitrectomy with vitreous shaving without scleral buckling achieved approximately the same rate of anatomic success as vitrectomy with scleral buckling, traditionally scleral buckling is indicated in PVR. The scleral buckle is important for several reasons. The scleral buckle relieves peripheral anteroposterior retinal traction, this is very important, since it is not possible to remove 100% of epiretinal proliferation in many eyes with PVR. The buckle helps to relieve circumferential retinal traction by reducing the circumference of the equatorial and anterior sclera. The buckle provides support to the peripheral retina, which may prevent recurrent RD when there is reproliferation after surgery. Finally, the buckle helps to isolate the peripheral retina from the posterior retina, forming a new, more posterior “ora serrata” on the crest of the buckle. This allows the posterior retina to remain attached in some eyes in which there is peripheral RD because of peripheral epiretinal proliferation.40 Because of the limited support offered by segmental buckles, we prefer encircling procedures when possible. Encircling procedures are particularly indicated in PVR of grade B or greater. We prefer solid silicon elements for encircling procedures because of their compressibility, encircling sponges tend to result in a variable undulating contour to the buckle unless multiple sutures are placed in each quadrant.

Lensectomy and Intraocular Lens In cases with primarily posterior PVR, lensectomy can frequently be avoided and subsequent postoperative inflammation reduced. A lensectomy is performed if the lens is too opaque to allow adequate visualization of the retina or if the lens is impending the ability to perform anterior dissection of epiretinal tissue. To prevent traction on the retina, removal of the anterior vitreous should be performed before lensectomy if the latter is going to be done by/via pars plana. The crystalline lens is removed via pars plana by phacofragmentation if necessary, and the capsule is removed by grasping the peripheral capsule with the end opening of a diamond coated forceps or using the vitrectomy probe to cut and aspirate the capsule, which is facilitated by indenting the anterior sclera. An intraocular lens (IOL) is generally not inserted at this time, since the presence of the IOL can impair visualization of the retina and the posterior

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297 IOL surface can act as a scaffold for reproliferation. An IOL may be implanted 4–6 months later for visual rehabilitation.40 It has been suggested that only polymethylmethacrylate lenses, with a 6.5 mm optical zone, be implanted in diabetic patients to facilitate postoperative examination and treatment of the posterior segment. If we choose to implant an IOL at the time of the vitrectomy surgery a convex-plano optical design may offer certain optical advantages, such as less refractive change in eyes which require fluid-gas exchange or silicone oil tamponade. If a foldable IOL is to be used, acrylic IOLs are preferred to silicone IOLs. Water condenses on the posterior face of the silicone IOL after fluid-gas exchange in eyes with a posterior capsulotomy, and visualization of the retina is very poor as a result of this condensation phenomenon. For this reason silicone lens should be avoided. Sometimes it may be necessary to explant a silicone IOL to improve visualization of the retina during PVR surgery. Clinical judgment must guide the determination of which IOL must be removed. If the PVR is primarily posterior, one could opt to leave the lens in place. The presence of the lens does not usually impair posterior dissection techniques, but during fluid-gas exchange, visibility can occasionally be reduced owing to any number of reasons. Air or silicone oil can gain access into the anterior chamber, making adequate optical correction difficult. Condensation on the posterior lens surface can impair the view of the posterior pole, necessitating wiping of the lens with a soft-tipped silicone tube or coating the lens with a viscoelastic substance. It is more common need to remove anterior chamber lenses than posterior chamber lenses. Posterior chamber IOLs may have to be removed in eyes in which extensive anterior dissection must be performed to mobilize the peripheral retina. Furthermore, in eyes receiving both silicone oil and relaxing retinotomy, higher IOP and lower proportion of hypotony were found where a native lens or intraocular implant is absent. So, removal of the lens or intraocular implant may be considered for those eyes at greatest risk of hypotony.50

VITRECTOMY FOR PROLIFERATIVE VITREORETINOPATHY The main surgical goals in managing PVR include closing the retinal breaks, sealing the retinal breaks, and completely releasing all periretinal traction. Although, almost all eyes with PVR have a PVD, after removing the central and posterior vitreous, the surgeon needs to debulk as much of the anterior basal gel as possible. Taking care to avoid creating any peripheral retinal breaks the peripheral vitreous is removed aggressively, since the residual vitreous base may serve as a scaffold for reproliferation and can lead to anterior RD postoperatively. The vitreous base proliferation is best removed by indenting the peripheral sclera with a cotton tipped applicator or scleral depressor and removing the vitreous under direct visualization through the operating microscope with a wide-angle viewing systems.51 It is essential that sufficient vitreous base traction be removed to allow the peripheral retina to remain reapposed to the RPE.

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Removal of Posterior Epiretinal Proliferation The epiretinal proliferation is removed by using a pick, forceps, or both. Most membranes can be elevated and removed with a vitreoretinal pick. The pick is used to check within the valley of the retinal folds to look for epiretinal membranes. Bimanual dissection using lighted picks and lighted forceps are helpful, since they allow counter traction to be placed on the retina to aid in separating membranes from the retina.40

Removal of Anterior Epiretinal Proliferation Two different approaches can be done to manage anterior PVR. The best anatomic and visual results are obtained by directly releasing the anterior traction with anterior membrane dissection. Perfluorocarbon liquid is used to fill one-third to one-half of the vitreous cavity. The PFC pushes the posterior retina against the posterior eye wall, which stretches the peripheral retina. This helps to stabilize the peripheral retina during dissection and helps to demonstrate where the epiretinal proliferation is located.52 It is often helpful to perform the anterior dissection under direct illumination of the operating microscope, with the surgeon indenting and rotating the peripheral sclera. The light pipe may be held adjacent to the external limbus by the assistant and directed toward the peripheral retina to improve illumination of the anterior retina/ciliary body. The surgeon may then use one hand to hold a pick and the other to hold forceps to allow bimanual dissection. Panoramic (wide-angle) viewing systems are very useful in performing the anterior dissection, since these systems allow a better view of the peripheral retina.40 In severe anterior PVR, the peripheral retina is pulled toward the ciliary body, making a circular trough. The membrane that forms a bridge between the folded retina and the ciliary body or the iris, is cut with curved or angled scissors. The second approach, by retinotomies and retinectomies, is used in some eyes that have very adherent peripheral vitreous base proliferation that cannot be separated from the retina with any technique and must be considered if the surgeon is convinced that the scleral buckle will not adequately support the residual retinal traction.40,53

Removal of Subretinal Proliferation Subretinal dissection should be left to the end of the removal of epiretinal membrane because in most cases it is not necessary to remove a subretinal membrane in order to reattach the retina; so then, bands may be left in the eye if they are distant from retinal breaks and are not causing any traction. Subretinal fibrosis will sometimes relax enough to allow retinal reattachment, so in most cases an attempt to flatten the retina with PFCL or air may be warranted to determine if removal of the membranes is necessary. In general,

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299 there are two surgical approaches depending on the type of subretinal membrane: (1) In single, multiple, or branching subretinal bands, if they are localized near a retinal break subretinal fibrosis can be removed via the retinal break(s), however a retinotomy as far away from the posterior pole and adjacent as possible to the membrane must be created to remove subretinal fibrosis if it cannot be removed via any existing retinal break. Subretinal fibrosis is rarely adherent to the retina, so grasping the subretinal band with a pick and bringing it to the retinotomy usually allows easy removal with an intraocular forceps, and (2) Subretinal bands may form an annular ring around the optic nerve or be a diffuse sheet in eyes with chronic RD with or without PVR. With a large sheet of membrane sometimes a larger anterior circumferential retinectomy should be created. It may be necessary to fold the retina over to gain access to the subretinal space so that the membrane can be removed with a bimanual technique. Scissors can be used to cut a subretinal membrane in the form of an annular band. Then forceps are used to remove the annular band from the eye.54

Relaxing Retinotomies and Retinectomies As a general rule, a relaxing retinotomy (in which the retina is cut but not excised) is made if the retina remains shortened after complete membrane removal; retinectomy (to excise membranes and involved retina) is done if membranes remain and a scleral buckle cannot relieve traction. Retinal shortening in PVR is divided into seven categories: 55 1. Focal contraction: Because it is localized, focal contraction has little effect on the overall configuration of the RD. 2. Diffuse posterior contraction: It is rarely necessary to cut the retina in focal or diffuse contraction. Occasionally when the retina is atrophic, the membranes will not strip from the retina without extensive retinal tearing. Diathermy is applied to the retina surrounding the area to be excised, particularly to the retinal vessels. The retina is most safely excised with scissors. 3. Circumferential contraction: A ridge of equatorial retina may sometimes remain in a circular contracted state even after excision of the posterior hyaloid and sectioning of circumferential membranes. The first two steps in relief of circumferential contraction are placement of a scleral buckle and extensive membrane dissection. With the vitrectomy instrument the vitreous should be cut to the retinal surface anteriorly to the posterior edge of the vitreous base. Any stripping anteriorly beyond this margin can result in retinal break. Remaining circumferential membranes should be sectioned with multiple radial cuts, being careful not to cut into elevated ridge of retina. Radial cuts, which may or may not be complete, are made at the posterior border of the vitreous base. Incomplete cuts that do not extend along the entire vitreous base will still relieve the circumferential

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300 traction and allow for retinal reattachment. The vitreous base should be excised during scleral depression. Perfluorocarbon liquids can show if we need a relaxing retinotomy at the posterior aspect of the vitreous base. With the posterior retina held in place by the PFCL and after a double row of endodiathermy, the retinotomy is extended circumferentially into normal appearing retina on each end of the retinotomy and then extended anteriorly to the ora serrata or the ciliary body if the pars plana is involved with traction. The retinectomy needs to be extended at the point that allows the retina to flatten. The anterior flap of the retina and membranes upon it are usually excised to reduce the risk of postoperative proliferation and contraction. 4. Anterior retinal displacement: Certain techniques may be useful, such as placing the infusion cannula as anteriorly as necessary to avoid subretinal infusion (1.5 mm behind the limbus). Scleral depression and bimanual techniques are also required. It is necessary to remove the lens with the capsule to perform an adequate peripheral dissection. Anterior peripheral vitreous is removed with the vitreous cutter using scleral depression and coaxial illumination. If the retina is displaced anteriorly, it may be possible to release traction by incising the forward displaced posterior hyaloid with a sharp MVR blade or with the vitreous cutting instrument, but most often it is necessary to section the membranes that form on the surface of the vitreous base with vitreoretinal scissors, that may or may not be followed by radial cuts in the remaining membrane to further release circumferential traction (Fig. 20).56 If excessive traction persists, an anterior retinotomy is performed after all posterior membranes have been removed just posterior to the anterior retinal traction. Lewis et al.57 performed initial vitreoretinal surgery on 81 eyes with RRD complicated by severe PVR. They performed vitreous base dissection on all 18 eyes that had anterior PVR. With one vitreoretinal operation, 66 of 81 eyes (81%) remained totally reattached. The main cause of initial anatomic failure and reoperation was either new or recurrent proliferation at the vitreous base. With additional vitreoretinal surgery 90% were totally reattached. The final causes of anatomic failure were anterior PVR and proliferation from relaxing retinotomies. 5. Intrinsic retinal contraction: Is often recognized only after injection of PFCL or insufflation of air. If the area of intrinsic retinal contraction is in the peripheral retina, the retinotomy should be extended circumferentially posterior to the area of contraction into normal retina at each end and anteriorly to the ora serrata (Fig. 21). When the intrinsic retinal contraction is localized in the posterior retina, we can get loss of visual field secondary to a circumferential retinotomy. Radial retinotomies can adequately relieve the traction; but these may extend too far posteriorly toward the optic nerve. Finally, excision of a section of nasal retina may adequately relieve traction on the more visually significant temporal retina.

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Figure 20  (Arevalo et al) Releasing tractional forces of proliferative vitreoretinopathy: relieving anterior displacement of the vitreous base. Anterior displacement of the vitreous base is relieved by incising the forward displaced posterior hyaloid (H) with a sharp myringotomy blade (M). Relaxing this posterior surface opens up the vitreous space collagenous tissue which is then debulked with a vitreous cutter (not shown). Endoilluminator (E) and infusion terminal (I) Source: Reprinted with permission from Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd S, Drews RC (Eds). Retinal and Vitreoretinal Surgery: Mastering the Latest Techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84.

Figure 21  (Arevalo et al) When the area of intrinsic retinal contraction is in the peripheral retina, the retinotomy should be extended circumferentially posterior to the area of contraction into normal retina at each end and anteriorly to the ora serrata. The anterior flap of retina needs to be excised (retinectomy), and laser photocoagulation applied. Cryotherapy may be used to create a chorioretinal adhesion anteriorly to the ora serrata

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302 6. Extensive periretinal fibrous proliferation: Usually occurs after trauma, retinal contusion or necrosis. The retina becomes replaced by fibrous tissue on both anterior or often the posterior sides of the retina. Membrane removal can result very difficult because in these areas, the retina may become very thin, contracted and shortened. The retina in these areas usually is nonfunctional and should be excised with the vitreous cutting instrument if it prevents retinal reattachment. 7. Contraction and fibrosis of the flap of a giant retinal tear: A GRT is often accompanied by the inward curling of the anterior retinal edge. The intrinsic elasticity of the retina initiates the curling process, with migration of the RPE cells over the edge to the ILM facilitating proliferation and contraction, which results in PVR. Even after removal on both the anterior and posterior membranes surface of the inward curling posterior flap of most GRTs, the edge may remain folded, requiring a retinotomy or retinectomy to allow complete flattening of the flap. Alternatively, a series of radial retinotomies may be placed approximately every 30° along the margin of the flap to allow unfolding.58 However, the irregular edge created by this series of retinotomies is more difficult to manage, and excision of the edge with the vitreous cutting instrument is the preferred approach.

Creating a Chorioretinal Adhesion We prefer to use laser photocoagulation over cryopexy in eyes with PVR because cryopexy causes greater breakdown of the blood-ocular barrier and may predispose for reproliferation and recurrent RD. It is important to remove all subretinal fluid via pre-existing posterior retinal breaks or creating with endodiathermy a drainage retinotomy distant from any potential source of traction, so that the retina will be completely flat against the RPE allowing laser photocoagulation to create a good adhesion. Laser photocoagulation should be applied utilizing an intravitreal fiberoptic laser probe. Some surgeons prefer to place a tight-scatter laser pattern in the entire peripheral retina to try to prevent recurrent RD. The advantage of extensive laser photocoagulation of the periphery is the creation of a chorioretinal burn that causes adherence of the retina to the RPE in the entire retinal periphery, which is prone to reproliferation and retinal breaks, but the disadvantage is that extensive laser photocoagulation causes greater breakdown of the blood-ocular barrier and creates thin retina over the laser burns, and this is more prone to tearing if there is recurrent proliferation.

Intraocular Tamponade The Silicone Study confirmed the superiority of silicone oil compared with sulfur hexafluoride (SF6) gas as an intraocular tamponade for the management of RD complicated by advanced grades of PVR.59 Eyes randomized to silicone

Chapter 14    Vitrectomy for Retinal Detachment with and without Proliferative. . .

303 oil were more likely to be successfully reattached, to achieve a visual acuity of 5/200 or better, and to have fewer postoperative complications than eyes randomized to SF6 gas. In contrast, the semipermanent tamponade of silicone oil offered little or no advantage compared with the prolonged but comparatively short-term tamponade with perfluoropropane (C3F8) gas.60 The Silicone Study has also shown that for the cohort of C3F8 gas- and silicone oil-treated eyes, there were similar outcomes between eyes that underwent a primary vitrectomy for PVR and eyes that had already undergone at least one unsuccessful vitrectomy with gas tamponade before enrollment into the study.61 In conclusion, there are two choices for intraocular tamponade in eyes with PVR. In general gas should be used for intraocular tamponade for several weeks if deemed adequate to reattach the retina. Silicone oil is used when tamponade for more than 4 weeks is necessary and depending on the severity of the case. Although the Silicone Study did not provide clear guidelines for when to use silicone oil and when to use gas, the physical properties of the two tamponade modalities make silicone oil preferable in some situations and gas preferable in others. Silicone oil may be preferred for patients who need to fly in an airplane postoperatively; some patients are unable to lie in a prone position as required for treatment with gas, and eyes at risk for hypotony. Conversely, gas may be preferred for eyes at risk for corneal touch by silicone oil, eyes with retinal breaks posterior to high scleral buckles (gas better conforms to the shape of the eye and scleral buckle), and eyes with intraoperative retinal or choroidal hemorrhages.62

Removal of Silicone Oil Some eyes require removal of silicone oil because of complications arising from the oil, such as glaucoma, emulsification of the silicone oil, band keratopathy, possible retinal toxicity and cataract. The timing of silicone oil removal remains controversial in different reports in the literature;63-65 however, we favor removal of silicone oil at 3–6 months to avoid complications. In Bassett et al66 series, there was no correlation between the silicone oil duration and the incidence of redetachment or other complications, as previously reported.64,67 They could not identify any significant risk factor for redetachment when the eyes with redetachment were compared to the eyes that remained attached.66 Recurrent RD occurs in 9–33% of eyes after removal of silicone oil in most series reported in the literature.60,63 However, the advent of wide-angle viewing systems, the introduction of the PFCL and sophisticated intraocular instruments and the actual capacity of the surgeon to manage the complexities of anterior PVR in recent years has shown that the rate of redetachment after oil removal is significantly lower than reported in previous series and the silicone study. In pseudophakic eyes, the silicone removal is carried out through a pars plana sclerotomy. In aphakic eyes, the oil is removed in the majority of cases through a small limbal paracentesis. In phakic eyes that did not have combined cataract extraction, the oil is removed via the pars plana, and finally in phakic eyes that

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304 underwent silicone oil removal combined with cataract extraction, a small posterior capsulotomy is performed with the vitrectomy probe or with capsular forceps, and the oil is removed through this opening. With this last technique, Bassett et al66 reported redetachment in 8.8% of all eyes and in 9.3% of the PVR eyes. With this technique the operating time is shorter than when silicone oil is removed via the pars plana, as new sclerotomies are not required. In addition, avoiding new sclerotomies may be associated with lesser risk for peripheral retinal break formation and postoperative vitreous hemorrhage. The central posterior capsulotomy eliminates the need for postoperative YAG capsulotomy.

Reoperations for Recurrent Retinal Detachment from Proliferative Vitreoretinopathy The timing or repeated surgery in eyes with recurrent RD from PVR is critical; early surgery may be associated with recurrent epiretinal proliferation, and late surgery is associated with poorer visual outcome if the retina is allowed to remain detached for 2–3 months while the surgeon waits for the proliferation to mature. The surgeon must determine which factor led to the recurrent RD and plan further surgery on the basis of this assessment. If the cause is reproliferation of epiretinal membranes, management consist of waiting until the proliferation is mature and then removing the recurrent proliferation. Any recurrent retinal breaks or new retinal breaks must be treated to create a stable chorioretinal adhesion. Recurrent RD within 1 week of initial surgery strongly suggests inadequate relief of traction at the time of initial surgery. Surgery in this setting may be performed promptly. Inadequate or misplaced scleral buckles are treated by replacing or revising the scleral buckle. Finally, insufficient chorioretinal adhesion may be treated by supplemental laser photocoagulation in the office as long as there is no subretinal fluid around the retinal break(s). In some cases, reoperations involving membrane surgery can be performed with silicone oil in situ68 whereas in others, it involves removal of silicone oil, membrane surgery, and internal tamponade with silicone oil or gas or just scleral buckling without revision of vitrectomy.

ADJUNCTIVE TREATMENT IN PROLIFERATIVE VITREORETINOPATHY There are a number of studies showing a potential benefit of a variety of pharmacological interventions, including retinoic acid,69 dexamethasone,70 colchicine,71 paclitaxel (Taxol),72 and daunorubicin.73 However, none of these regimens are in routine clinical use. Recently, there has been increasing interest in the use of a combination of 5-fluorouracil (5-FU) and low-molecular-weight heparin (LMWH) in the prevention of PVR and in established PVR. Because 5-FU and LMWH are effective in different aspects in the PVR process, it is believed that a synergistic approach to the prevention of PVR would be

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305 advantageous. Asaria et al74 reported a significant reduction in the incidence of postoperative PVR in patients receiving 5-FU and LMWH therapy and in the reoperation rate resulting from PVR. However Charteris et al75 found that a perioperative infusion of this combined adjunctive treatment does not significantly increase the success rate of vitreoretinal surgery for established PVR. A recent review done by Sundaram et al76 concluded that when only randomized controlled trials are compared the evidence is inconsistent. Due to the anti-inflammatory properties and the proved improvement visualization of the vitreous, delineation of posterior hyaloid and epiretinal membranes, triamcinolone acetonide has been used to allow a more complete and safer ERM removal during vitrectomy for PVR.77 However it is controversial if its use could improve the outcome of the surgery.78 Recently Ahmadieh et al in a randomized clinical trial reported that the outcomes of vitreoretinal surgery for established PVR are not improved significantly by adjunctive triamcinolone acetonide injection in silicone-filled eyes.79

GIANT RETINAL TEARS In an eye with a fresh GRT, a lens sparing vitrectomy with a scleral buckle may be performed. However, when there is a highly elevated anterior flap or PVR and the lens interferes with necessary vitreous base dissection and removal, a lensectomy must be performed. We place the scleral buckle before vitrectomy if the final posterior flap position can be accurately estimated before reattachment. Meticulous vitrectomy over the vitreous base is critical to release all anterior traction. Attention to the anterior flap is essential. If it is pulled anteriorly toward the pars plana or lens, attempts to release it are first made by removing vitreous gel. The release of the anterior flap should not be possible if the vitreous and anterior flaps are excised together. Perfluorocarbon liquids facilitate the unfolding of the flap of the tear while minimizing retinal trauma resulting from the use of microsurgical tools. Additionally, the need for a posterior retinotomy to remove subretinal fluid is obviated, since the weight of the PFCL forces the fluid anteriorly. If necessary, residual preretinal membranes are dissected under PFCL. As the PFC meniscus approaches the edge of the tear, inspection may reveal star folds and/or circumferential shortening of the tear from PVR. Additionally, the edge may assume a scrolled appearance from epiretinal membranes proliferation on the inner surface of the retina. Removal of the epiretinal membranes using bimanual dissection is easier, since the retinal flap is immobilized by PFCL. At this point, the meniscus of PFCL is kept just posterior to the margin of the tear. The basal vitreous gel is trimmed with the vitreous cutter for 360°, paying careful attention to the margin of the tear. Meticulous removal of the peripheral vitreous gel permits a more complete replacement of the vitreous volume if silicone oil tamponade is used, decreases the likelihood for new breaks along the posterior insertion of the vitreous base, and diminishes the occurrence of anterior PVR. With the use of PFCLs proper

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306 repositioning of the torn retina is achieved while endophotocoagulation or trans-scleral cryotherapy is applied to the posterior edge of the tear through the liquid. Cryotherapy application is more precise, excessive treatment can be avoided, and intravitreal dispersion of RPE cells during cryotherapy may even be reduced, since the PFC liquid presses the edge of the giant break against the RPE. Endophotocoagulation is the preferred method of retinopexy, but when the margin of the tear is too peripheral and cannot be visualized, cryopexy or indirect laser photocoagulation is used.

POSTOPERATIVE COMPLICATIONS It is well-recognized that the use of scleral explants combined with PPV repair of RD is associated with several risks including hypotony during placement of the buckle with associated choroidal hemorrhage,80-82 and longer duration of surgery.81 Postoperative complications include refractive change, 83,84 diplopia, 85,86 exoplant erosion or infection, 85,87 and a risk of decreased retinal blood flow88 and anterior segment ischemia.89,90 Early postoperative complications in PVR surgery are elevated IOP, excessive inflammation, infection, endophthalmitis and others. Late postoperative complications are recurrent epiretinal proliferation leading to RD, keratopathy, hypotony, rubeosis iridis, cataract, and cystoid macular edema. Finally, retinotomies and retinectomies are associated with intraoperative and postoperative hemorrhage, hypotony and recurrent RD.

SUMMARY In summary, this chapter has discussed the different vitrectomy techniques available to repair RD with and without PVR in a step-by-step approach. Pars plana vitrectomy, a method originally reserved for complicated cases, is now used increasingly for primary repair of uncomplicated RRD. Vitrectomy may be selected to diminish complications associated with scleral buckling, to help relieve vitreoretinal traction and/or to create a large empty vitreous cavity in which a tamponade can be introduced. Primary vitrectomy with and without a scleral buckling seems to be useful in complicated cases that have an unfavorable prognosis with simpler procedures. The selection of alternative techniques for different types of RD is a matter of surgeon preference. However, a variety of relatively complicated RRD are currently best managed with vitrectomy techniques with or without associated scleral buckling including RRD with PVR (Figs 22A and B), RRD associated with GRTs, RD associated with proliferative retinal vascular disease, RRD due to posterior breaks, RD associated with viral and other forms of retinitis, RD associated with posterior vitreoretinal traction, and RD associated with significant vitreous opacification.

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A

B

Figures 22A and B  (Arevalo et al) (A) Retinal detachment with proliferative vitreoretinopathy before and (B) after pars plana vitrectomy with silicone oil injection

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310 43. Girard P, Mimoun G, Karpouzas I, et al. Clinical risk factors for proliferative vitreoretinopathy after retinal detachment surgery. Retina. 1994;14(5):417-24. 44. Miyake K. Blood-retinal barrier in eyes with long-standing aphakia with apparently normal fundi. Arch Ophthalmol. 1982;100(9):1437-9. 45. Asaria RH, Kon CH, Bunce C, et al. How to predict proliferative vitreoretinopathy: a prospective study. Ophthalmology. 2001;108(7):1184-6. 46. Fuller DG, Laqua H, Machemer R. Ultrasonographic diagnosis of massive periretinal proliferation in eyes with opaque media (triangular retinal detachment). Am J Ophthalmol. 1977;83(4):460-4. 47. Machemer R, Aaberg TM, Freeman HM, et al. An updated classification of retinal detachment with proliferative vitreoretinopathy. Am J Ophthalmol. 1991;112(2):159-65. 48. Oyagi T, Emi K. Vitrectomy without scleral buckling for proliferative vitreoretinopathy. Retina. 2004;24(2):215-8. 49. Tan HS, Mura M, Oberstein SY, et al. Primary retinectomy in proliferative vitreoretinopathy. Am J Ophthalmol. 2010;149(3):447-52. 50. Tseng JJ, Schiff WM, Barile GR, et al. Influence of postoperative lens status on intraocular pressure in proliferative vitreoretinopathy. Am J Ophthalmol. 2009;147(5):875-85. 51. Murray TG, Boldt HC, Lewis H, et al. A technique for facilitated visualization and dissection of the vitreous base, pars plana, and pars plicata. Arch Ophthalmol. 1991;109(10):1458-9. 52. Scott IU, Flynn HW, Murray TG, et al. Outcomes of surgery for retinal detachment associated with proliferative vitreoretinopathy using perfluoro-n-octane: a multicenter study. Am J Ophthalmol. 2003;136(3):454-63. 53. Iverson DA, Ward TG, Blumenkranz MS. Indications and results of relaxing retinotomy. Ophthalmology. 1990;97(10):1298-304. 54. Lewis H. Proliferative vitreoretinopathy (PVR). In: Boyd BF, Boyd SL, Drews RC (Eds). Retinal and vitreoretinal surgery: Mastering the latest techniques, 1st edition. Panama: Highlights of Ophthalmology; 2002. pp. 459-84. 55. Abrams GW, Nanda SK. Retinotomies and retinectomies. In: Ryan SJ, Wilkinson CP (Eds). Retina, 3rd edition. Mosby: St. Louis Missouri; 2001. pp. 2317-48. 56. Lewis H, Aaberg TM. Anterior proliferative vitreoretinopathy. Am J Ophthalmol. 1988;105(3):277-84. 57. Lewis H, Aaberg TM. Causes of failure after repeat vitreoretinal surgery for recurrent proliferative vitreoretinopathy. Am J Ophthalmol. 1991;111(1):15-9. 58. Machemer R. Retinotomy. Am J Ophthalmol. 1981;92(6):768-74. 59. Vitrectomy with silicone oil or sulfur hexafluoride gas in eyes with severe proliferative vitreoretinopathy: results of a randomized clinical trial. Silicone Study Report 1. Arch Ophthalmol. 1992;110(6):770-9. 60. Vitrectomy with silicone oil or perfluoropropane gas in eyes with severe proliferative vitreoretinopathy: results of a randomized clinical trial. Silicone Study Report 2. Arch Ophthalmol. 1992;110(6):780-92. 61. McCuen BW, Azen SP, Stern W, et al. Vitrectomy with silicone oil or perfluoropropane gas in eyes with severe proliferative vitreoretinopathy. Silicone Study Report 3. Retina. 1993;13(4):279-84. 62. Abrams GW, Azen SP, McCuen BW, et al. Vitrectomy with silicone oil or long-acting gas in eyes with severe proliferative vitreoretinopathy: results of additional and long-term follow-up. Silicone Study report 11. Arch Ophthalmol. 1997;115(3):335-44.

Chapter 14    Vitrectomy for Retinal Detachment with and without Proliferative. . .

311 63. Casswell AG, Gregor ZJ. Silicone oil removal. II. Operative and postoperative complications. Br J Ophthalmol. 1987;71(12):898-902. 64. Hutton WL, Azen SP, Blumenkranz MS, et al. The effects of silicone oil removal. Silicone Study Report 6. Arch Ophthalmol. 1994;112(6):778-85. 65. Scholda C, Egger S, Lakits A, et al. Retinal detachment after silicone oil removal. Acta Ophthalmol Scand. 2000;78(2):182-6. 66. Bassat IB, Desatnik H, Alhalel A, et al. Reduced rate of retinal detachment following silicone oil removal. Retina. 2000;20(6):597-603. 67. Barr CC, Lai MY, Lean JS, et al. Postoperative intraocular pressure abnormalities in the Silicone Study. Silicone Study Report 4. Ophthalmology. 1993;100(11):162935. 68. Sharma T, Gopal L, Shanmugam MP, et al. Management of recurrent retinal detachment in silicone oil-filled eyes. Retina. 2002;22(2):153-7. 69. Fekrat S, de Juan E, Campochiaro PA. The effect of oral 13-cis-retinoic acid on retinal redetachment after surgical repair in eyes with proliferative vitreoretinopathy. Ophthalmology. 1995;102(3):412-8. 70. Tano Y, Sugita G, Abrams G, et al. Inhibition of intraocular proliferations with intravitreal corticosteroids. Am J Ophthalmol. 1980;89(1):131-6. 71. Lemor M, Yeo JH, Glaser BM. Oral colchicine for the treatment of experimental traction retinal detachment. Arch Ophthalmol. 1986;104(8):1226-9. 72. Daniels SA, Coonley KG, Yoshizumi MO. Taxol treatment of experimental proliferative vitreoretinopathy. Graefes Arch Clin Exp Ophthalmol. 1990;228(6):513-6. 73. Wiedemann P, Hilgers RD, Bauer P, et al. Adjunctive daunorubicin in the treatment of proliferative vitreoretinopathy: results of a multicenter clinical trial. Daunomycin Study Group. Am J Ophthalmol. 1998;126(4):550-9. 74. Asaria RH, Kon CH, Bunce C, et al. Adjuvant 5-fluorouracil and heparin prevents proliferative vitreoretinopathy: Results from a randomized, double-blind, controlled clinical trial. Ophthalmology. 2001;108(7):1179-83. 75. Charteris DG, Aylward GW, Wong D, et al. A randomized controlled trial of combined 5-fluorouracil and low-molecular-weight heparin in management of established proliferative vitreoretinopathy. Ophthalmology. 2004;111(12):2240-5. 76. Sundaram V, Barsam A, Virgili G. Intravitreal low molecular weight heparin and 5-Fluorouracil for the prevention of proliferative vitreoretinopathy following retinal reattachment surgery. Cochrane Databse Syst Rev. 2010;7:CD006421. 77. Ueno A, Enaida H, Hata Y, et al. Long-term clinical outcomes and therapeutic benefits of triamcinolone-assisted pars plana vitrectomy for proliferative vitreoretinopathy: a case study. Eur J Ophthalmol. 2007;17(3):392-8. 78. Acar N, Kapran Z, Altan T, et al. Pars plana vitrectomy with and without triamcinolone acetonide assistance in pseudophakic retinal detachment complicated with proliferative vitreoretinopathy. Jpn J Ophthalmol. 2010;54(4):331-7. 79. Ahmadieh H, Feghhi M, Tabatabaei H, et al. Triamcinolone acetonide in siliconefilled eyes as adjunctive treatment for proliferative vitreoretinopathy: a randomized clinical trial. Ophthalmology. 2008;115(11):1938-43. 80. Gartry DS, Chignell AH, Franks WA, et al. Pars plana vitrectomy for the treatment of rhegmatogenous retinal detachment uncomplicated by advanced proliferative vitreoretinopathy. Br J Ophthalmol. 1993;77(4):199-203. 81. Hakin KN, Lavin MJ, Leaver PK. Primary vitrectomy for rhegmatogenous retinal detachment. Graefes Arch Clin Exp Ophthalmol. 1993;231(6):344-6.

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312 82. Tabandeh H, Sullivan PM, Smahliuk P, et al. Suprachoroidal hemorrhage during pars plana vitrectomy. Risk factors and outcomes. Ophthalmology. 1999;106(2):236-42. 83. Rubin ML. The induction of refractive errors by retinal detachment surgery. Trans Am Ophthalmol Soc. 1975;73:452-90. 84. Goel R, Crewdson J, Chignell AH. Astigmatism following retinal detachment surgery. Br J Ophthalmol. 1983;67(5):327-9. 85. Arruga A. Motility disturbances induced by operations for retinal detachment. Mod Probl Ophthalmol. 1977;18:408-14. 86. Fison PN, Chignell AH. Diplopia after retinal detachment surgery. Br J Ophthalmol. 1987;71(7):521-5. 87. Flindall RJ, Norton EW, Curtin VT, et al. Reduction of extrusion and infection following episcleral silicone implants and cryopexy in retinal detachment surgery. Am J Ophthalmol. 1971;71(4):835-7. 88. Yoshida A, Feke GT, Green GJ, et al. Retinal circulatory changes after scleral buckling procedures. Am J Ophthalmol. 1983;95(2):182-8. 89. Ryan SJ, Goldberg MF. Anterior segment ischemia following scleral buckling in sickle cell hemoglobinopathy. Am J Ophthalmol. 1971;72(1):35-50. 90. Kwartz J, Charles S, McCormack P, et al. Anterior segment ischaemia following segmental scleral buckling. Br J Ophthalmol. 1994;78(5):409-10.

chapter 15

Current Indications of Antiangiogenics in Vitrectomy Mauricio Maia, Fernando M Penha, J Fernando Arevalo

antiangiogenics: overview Introduction: Vascular Endothelium Growth Factor The vascular endothelium growth factor (VEGF) is a joint of proteins including the platelet growth factor, VEGF-A, VEGF-B, VEGF-C, VEGF-D and the VEGF-E.1 The well-known VEGF-A is a dimeric protein of nine different isoforms synthesized by RNAm. Four of the isoforms are: VEGF-121, VEGF-165, VEGF-179, VEGF-206.1 The subtypes VEGF-A are related to cellular migration and proliferation as well as the synthesis of the VEGF tube throughout variety of different pathways which is the common final event in the activation of the protein kinases using three VEGF receptors: VEGF-R1, VEGF-R2, VEGF-R3. It is known that VEGF-A results in increasing of the vascular permeability as well as neovascularization due to specific portions of the plasmatic membrane from endothelial cells that are highly permeable for macromolecules named vesicular/vacuolar.1 The cytokines from VEGF are related to the upregulation and downregulation of the physiological activities during the embryogenesis in human eyes.1 This chapter will discuss causes, management and prevention of intraoperative bleeding during pars plana vitrectomy (PPV), emphasizing the state-of-the-art regarding the use of antiangiogenics before PPV in proliferative diabetic retinopathy (PDR) in order to minimize the intraoperative bleeding.

Role of Bevacizumab and Ranibizumab in the Angiogenesis Process It is known that PPV is generally indicated when the tractional retinal detachment (TRD) is involving the macular area or there is a macular-

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314 threatening condition.2 However, sometimes the postoperative functional result may not be as good as the anatomical outcome.1-4 The surgical technique includes removal of the fibrovascular membranes and relief of vitreoretinal traction.1-3 Particular attention is focused on minimizing intraoperative bleeding and avoiding iatrogenic retinal breaks.4-6 Intraoperative bleeding is one of the main complications associated with PPV in PDR and may hinder the surgical outcome or even be uncontrollable. In addition, intraoperative bleeding during PPV increases the risk of vitreous hemorrhage in the early postoperative period, further emphasizing the need for careful hemostasis during surgery.1-6 The intravitreal injection of bevacizumab 1.25 mg in eyes with PDR reduces the neovascularization when used 3–5 days prior to PPV; this facilitates the vitreoretinal surgical procedure and decreases the risks of intraoperative hemorrhage.7-10 However, surgeons must be aware about the possibility to induce worsening of TRD in 5.4% of young patients with previous initial TRD.11 Additionally, eyes with PDR and initial vitreous hemorrhage may have a faster blood reabsorption rate than natural history. This may also be used as an adjuvant therapy at the end of the PPV in complex cases in order to decrease the possibility of iris neovascularization in complicated cases of PDR.12-14 The prospective Comparison of Age-Related Macular Degeneration Treatments Trials study (CATT), a large National Institute of Health (NIH) sponsored trial, reported similar risks of thromboembolic events in eyes submitted to intravitreal bevacizumab injection versus intravitreal ranibizumab injection in eyes with age-related macular degeneration (AMD).15 Similar safety profile was observed by a retrospective study of the Pan-American Collaborative Retina Study Group (PACORES) in 4,303 eyes with different vitreoretinal diseases such as PDR, DMR, cystoid macular edema in pseudophakic eyes, central retinal vein occlusion, AMRD and branch retinal vein occlusion.16 Ranibizumab has been widely used for the treatment of several choroidal and retinal vascular diseases as well as in patients with TRD and PDR undergoing PPV to avoid bleeding after the surgery. 17 The intravitreal injection of 0.5 mg of ranibizumab is associated with regression of persistent neovascularization in eyes with PDR when used 3–5 days preoperative for the management of patients with TRD in PDR eyes; this also minimizes intraoperative bleeding, thus facilitating the surgery and contributing to a better outcome due to a decrease in the surgical duration, similar to the observations of the intravitreal effects of bevacizumab injection 3–5 days prior to PPV in PDR eyes.17

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INTRAOPERATIVE BLEEDING DURING PARS PLANA VITRECTOMY IN PROLIFERATIVE DIABETIC RETINOPATHY Introduction Intraoperative bleeding during PPV is a challenge for the surgeon and has been a matter of debate regarding techniques for controlling these hemorrhages. Massive intraoperative bleeding is correlated to histological damage due to high degree of hemosiderin deposit into the retina.18,19 High volumes of blood clot retraction can produce secondary TRD, retinal holes and subretinal accumulation of blood.19 Bleeding during the surgical procedure may impair surgical field, thus yielding poor postoperative results including low vision, proliferative vitreoretinopathy (PVR) and secondary retinal detachment. Prevention as well as the correct management of intraoperative bleeding is important to achieve good surgical results. Meticulous surgical technique is essential to prevent intraocular hemorrhage; however, when bleeding occurs, it must be promptly controlled.

Vitreoretinal Bleeding Vitreous hemorrhage may occur during dissection, segmentation and delamination of fibrovascular membranes from PDR. Particularly, focal fibrovascular adhesions have less chance of persistent bleeding as compared to plaques. However, it may be controlled using many techniques such as: rising of intraocular pressure (IOP), utilization of backflush device, endodiathermy, perfluorocarbon liquid (PFCL) and fluid-air exchange. Unimanual or bimanual bipolar diathermy is routinely applied to sites of persistent bleeding other than the optic nerve. Avoiding segmentation of highly vascularized membranes and ensuring that the patient’s blood pressure is normal can reduce the incidence of hemorrhage. Elevation of IOP is used to minimize bleeding during the dissection of vascular tissue. Adjusting IOP to a level above systolic blood pressure for 1–2 minutes will frequently stop persistent bleeding in patients with normal values of blood pressure.20-22 It is important to emphasize that any blood on the retina should be removed immediately, before clot formation. Clotted blood should be cautiously stripped from the retina, as it may be tightly adhered. In some circumstances, scissors, forceps or vitrectomy tip may be necessary to excise a clot.20-22 Recently, prevention of intraoperative bleeding may be performed by intravitreal injection of anti-VEGF (ranibizumab 0.5 mg or bevacizumab 1.25 mg) applied 3–5 days before the vitrectomy (see session below). This is a common technique performed preoperatively in vitreoretinal surgery for PDR; adequate preoperative blood pressure control as well as a normal systemic blood

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316 coagulation status is also very important to avoid intraoperative bleeding during vitreoretinal surgeries from many etiologies. Blood into the vitreous cavity may also occur during dissection of PVR starfold membrane. Care must be taken when performing peeling close to major vessels or near to the optic disk. Large vein rupture may cause intense bleeding at the posterior pole, followed by difficulty to remove big clots, mainly in the macula region that may aggravate low vision and PVR in the postoperative period.20-22 The backflush system connected to a vitrectomy probe is an important surgical maneuver in order to remove blood from the fovea; in this technique, a reverse flow from the vitreous probe is achieved and using the mechanical flow of balanced salt solution (BSS), the clot is “washed” nicely from the posterior pole.23-25 Some surgeons do prefer to perform posterior retinotomy at the nasal retina in order to make subretinal fluid drainage during fluid-air exchange. An adequate retinotomy away from large vessels, endodiathermy of microvessels and deviation of vitrectomy aperture from large vessels may preclude bleeding either into the vitreous cavity or into the subretinal space.23-25 Subretinal clot may be disastrous to the postoperative visual and anatomic prognosis, leading to PVR formation and retinal redetachment. Slow and careful aspiration of bleeding with or without further rising of IOP may prevent its migration and the size of the clot. After controlling the hemorrhagic process, mechanical removal of blood may be difficult and it may result in severe outer retina atrophy.20-22 Intraoperative control of hemorrhage in penetrating ocular injuries may be a challenge to the surgeon. Some techniques (such as IOP rising, fluid-air exchange, endodiathermy, endophotocoagulation) must be known to be part of the surgical arsenal to avoid such complication.20

Preoperative procedures to minimize the possibility of intraoperative bLeeding Blood Pressure Control Preoperative blood pressure control could aid to prevent intraoperative bleeding during vitrectomy.

Antiplatelet and Anticoagulants—Is It Necessary to Discontinue Them before Surgery? Warfarin, the most commonly used anticoagulant, inhibits vitamin K dependent clotting factors (II, VII, IX and X) and need the International Normalized Ratio between 2–3 to maintain optimal anticoagulation (e.g. atrial fibrillation, valvular heart disease and thromboembolic diseases).26 There are two main

Chapter 15    Current Indications of Antiangiogenics in Vitrectomy

317 platelet aggregation pathways to be inhibited.26 Clopidogrel inhibits adenosine diphosphate-produced platelet aggregation. Aspirin works through the inhibition of the cyclooxygenase pathway and frequently has been used in combination with warfarin, although with less therapeutic efficacy than clopidogrel.26 The most common indication for antiplatelet therapy in vitrectomy candidates is cardiac stent, coronary artery bypass grafting and history of transient ischemic attack.27-30 Use of antiplatelet agents has increased in patients undergoing vitreoretinal surgery.27-30 However, there is no unified consensus regarding the risks of systemic anticoagulation or platelet inhibition during ocular surgery and whether continuation of such medication is appropriate.27-32 Warfarin use should be avoided if the patient’s thromboembolic risk is low because of high possibilities of either intraoperative and/or postoperative bleeding.27,28 Particularly, if a PDR patient with highly active neovascularization and TRD has a high risk of thromboembolic event, anticoagulation may be continued. Preoperative use of anti-VEGF and a fast as well as good quality small gauge surgery may contribute to induce lower rates of hemorrhagic events.

Intravitreal Injection of Anti-VEGF Inhibitors in Proliferative Diabetic Retinopathy Important evidences have shown the benefits of intravitreal anti-VEGF therapy 3–5 days before vitrectomy for PDR and this is an important preoperative adjuvant therapy performed worldwide in order to facilitate the PPV and minimize the bleeding during the surgical procedure.

INTRAVITREAL INJECTION OF ANTI-VEGF BEFORE SURGERY IN PROLIFERATIVE DIABETIC RETINOPATHY Rationale Regression of neovascularization before surgery results in less intraoperative bleeding and contributes to an easier PPV procedure in PDR.

Intravitreal Bevacizumab Before Pars Plana Vitrectomy In Proliferative Diabetic Retinopathy Intravitreal bevacizumab administration 3–5 days prior to PPV results in a decrease of intraoperative bleeding during PPV in patients with advanced PDR 8-14,33,34 (Figs 1A to F). A recent update review of 698 intravitreal injections of bevacizumab from the PACORES group has detected an incidence of progression of TRD in 3.5% of the cases.34 The time period between bevacizumab administration and PPV should be less than 7 days in order to reduce the risk of increased vitreoretinal traction due to excessive contraction of fibrotic tissue induced by the abrupt decrease of VEGF levels in patients

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A

B

C

D

E

F

Figures 1A to F  Infrared, autofluorescence and fluorescein angiography performed at the 30th postoperative day of right eye submitted to vitrectomy in proliferative diabetic retinopathy. Best corrected visual acuity improved from hand movements to 20/25. (A) Infrared image showing normal macula. The anatomy of optic disk is abnormal due to chronic glaucoma; (B) Autofluorescence showing no abnormalities at the fovea; (C) Fluorescein angiogram from the macula showing no edema or leakage; (D) Fluorescein angiogram showing no active neovascularization and two big scars temporal superiorly/inferiorly to the macula due to diathermy; (E) Late phase of fluorescein angiogram showing similar findings; (F) Fluorescein angiogram at the nasal retina showing no active neovessels

with advanced PDR submitted to intravitreal injection of VEGF inhibitors.11 This leads to regression of neovascularization and less bleeding during the PPV—usually performed 3 days after the intravitreal anti-VEFG injection; it results in a fast vitreoretinal surgery which is especially useful in eyes with glaucoma associated with PDR8-14,33,34(Figs 1A to F). As the theoretical risk factors for this complication is the abrupt inhibition of VEGF, it is recommended that only 1.25 mg of bevacizumab (instead of 2.5 mg) be used in order to avoid excessive fibrotic contraction.11 The possible risk factors for progression of TRD in PDR are: uncontrolled systemic diabetes, previous TRD, type I diabetes and the attached hyaloid to the retina11 (Figs 1E and F). Decrease of intraoperative bleeding was observed in around 85% of eyes compared to sham group following 1.25 mg of bevacizumab injection into the vitreous cavity 1 week prior to PPV. Lowest dose of bevacizumab (0.16 mg) was as effective as the standard dose (1.25 mg) in reducing intraoperative

Chapter 15    Current Indications of Antiangiogenics in Vitrectomy

319 hemorrhage when administered 3 days before surgery.9 A recent meta-analysis showed that the incidence of intraoperative bleeding and frequency of endodiathermy were significantly lower following intravitreal bevacizumab injection before the surgery in PDR compared to surgery without previous anti-VEGF injection.14 Nowadays it is suggested that 1.25 mg of intravitreal bevacizumab injection be performed 3 days before the vitrectomy in PDR (Figs 1A and B). This preoperative technique allows that PPV be performed even in complex surgical cases with minimal ocular trauma (Figs 1E and F). However, the surgeon must be aware about the possibility of worsening the previous TRD; the estimated risk evaluated by retrospective study is around 5.4%.9,34

Intravitreal Ranibizumab before Pars Plana Vitrectomy in Proliferative Diabetic Retinopathy Differences regarding the intraoperative bleeding were also observed following intravitreal injection of ranibizumab (0.5 mg) 7 days before vitrectomy for TRD management.17 Incidence of intraoperative hemorrhage was decreased by 65% when compared to sham group.17 However, no data regarding the risk of inducing TRD is available due to low number of cases reported in the literature. In summary, intravitreal injection of 0.5 mg of ranibizumab is a useful tool in order to decrease the amount of intraoperative bleeding in PDR but is also recommended that PPV be performed around 3–5 days after intravitreal injection.

Technique of Preoperative Intravitreal Anti-VEGF Injection The surgical technique of intravitreal anti-VEGF injections 3–5 days before PPV in PDR must be performed similarly to the technique used for the management of choroidal neovascularization in AMD (Box 1). All eyes with PDR due to TRD and/or vitreous hemorrhage that will be submitted to PPV should be treated by intravitreal antiangiogenic injection Box 1: Key points for successful anti-VEGF injections before pars plana vitrectomy in proliferative diabetic retinopathy 1. Perform the intravitreal injection under sterile conditions 2. Prophylaxis for endophthalmitis using 5% topical Povidone Iodine 3. Use either 1.25 mg of bevacizumab or 0.5 mg of ranibizumab 4. Be aware that progression of previous tractional retinal detachment or development of tractional retinal detachment may occur after intravitreal anti-VEGF injection in proliferative diabetic retinopathy. For this reason, the pars plana vitrectomy must be performed 3 to 5 days after intravitreal anti-VEGF injection in proliferative diabetic retinopathy eyes.

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320 (either 1.25 mg of bevacizumab or 0.5 mg of ranibizumab) 3–5 days before the PPV. The procedure should be performed in the operating room, under sterile conditions using the sterile drape and topical anesthesia. After the eye speculum is inserted, the eye should be submitted to topical instillation of Povidone Iodine 5% and the surgeon should wait for a minimum of 15–45 seconds; so, the eye should be washed by BSS irrigation.. Paracentesis is not necessary but it may be used in glaucomatous eyes. The surgeon must give an intravitreal injection at 2.5 mm posterior to the limbus in pseudophakic eyes and 3.5–4.0 mm posterior to the limbus in phakic eyes. Intravitreal injection of 1.25 mg of bevacizumab (0.05 ml of bevacizumab 25 mg/ml) or 0.5 mg of ranibizumab (0.05 ml of ranibizumab 10 mg/ml) must be performed after the half of the 29-gauge needle been inserted into the vitreous cavity with the needle positioned towards the optic disk. The surgeon should wait around 5 seconds before the needle removal. As soon as the needle is removed from the eye, the surgeon holds the wound using the cotton tip against the scleral wound during 5–10 seconds.

Care During Preoperative Intravitreal Anti-VEGF Injection Before Pars Plana Vitrectomy in Proliferative Diabetic Retinopathy Conclusion of Intravitreal Injection of Anti-VEGF Before Proliferative Diabetic Retinopathy The anti-VEGF therapy before PPV for management of PDR is a procedure performed worldwide and a very helpful adjuvant technique which minimizes bleeding during PPV in PDR eyes. Surgeons should use either 1.25 mg of bevacizumab or 0.5 mg of ranibizumab as well as plan the PPV procedure around 3 days after anti-VEGF procedure due to the possibility of worsening or development of TRD in PDR eyes.

techniques OF INTRAOPerative posterior segment bleeding control There are several ways to control intraocular hemorrhage and all of them follow three basic principles: 1. Compressive effect over the vessels by fluids and/or increasing IOP that leads to vasoconstriction and clot formation; these maneuvers do not require a direct contact of instruments with the bleeding vessels and are especially useful for hemorrhage in the macular area and optic disk.20-22 2. Induction of pharmacological vasoconstriction reducing the vascular permeability;35-37 these maneuvers do not also require a direct contact

Chapter 15    Current Indications of Antiangiogenics in Vitrectomy

321 of instruments with the bleeding vessels and are especially useful for hemorrhage in the macular area and optic disk; however they are not often used by vitreoretinal surgeons. 3. Direct thermal effect over the blood, leading to local coagulation of the blood and resulting in a clot formation; these maneuvers require a direct contact of instruments with the bleeding vessels and are especially useful for hemorrhage outside of the macular area and/or optic disk.23-25 Based on these principles, the management of intraoperative hemorrhage may be organized in a following didactic way:

Rising the Intraocular Pressure It is a rapid and common technique for controlling the intraoperative hemorrhage. Thrombosis and hemostasis occur with difficulty under fluid-filled medium. Thus, increasing of IOP is a useful maneuver to compress bleeding vessels and helps to decrease blood flow, resulting in clot formation and hemostasis which facilitates that key surgical steps such as posterior hyaloid detachment to be nicely performed, resulting in minimal hemorrhage20-22 (Figs 2A and B). In hypotonic eyes, the hemorrhage process tends to be a more frequent and complex event. Rising of IOP is achieved by lifting the infusion bottle or preferentially by increasing the pressure in the infusion system using a controlled mechanism.20-22 Estimated infusion pressure from the first method is not known. Nowadays, vitrectomy systems have enough resources to induce elevation of IOP in a controlled way, resulting in better outcomes of vitreoretinal surgeries. Intraocular pressure must be increased until optic disk pulsation is observed. Care must be taken in order to avoid the pale retina as well as pale optic nerve; this clinical feature indicates decrease of optic disk perfusion and it may result in postoperative irreversible visual loss due to iatrogenic ischemic optic neuropathy, especially if the increased IOP is continuously high for more than 5 minutes. Normally, the raised IOP must persist until the decrease of bleeding process and the observation of clot formation. In case residual active bleeding is observed, diathermy and/or endolaser may be used to control bleeding (Fig. 2C). Intraocular pressure elevation may range between 1 minute and 3 minutes, depending on case and variables such as size and number of bleeding sites, vessel caliber, the systemic status of blood coagulation as well as the blood pressure maintenance of remained closed system is important to keep the high and controlled levels of IOP. To achieve this goal, plugged sclerotomies, avoidance of frequent removal of instruments away from the eye or the preferred valved trocars systems (Fig. 2D) may help maintain a steady IOP during the surgery and a reasonable fluidic dynamics. The high IOP technique is especially useful for management of neovascularization at the anterior chamber in order to avoid bleeding; high IOP values must be used with care to avoid atrophic changes at the optic disk after surgery. Increased IOP may damage intraocular structures sensitive to ischemia. Particularly, care must be taken in eyes with glaucoma, ischemic optic

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A

B

C

D

Figures 2A to D  Surgical techniques for intraoperative bleeding control. (A) Initial stage of posterior hyaloid detachment in proliferative diabetic retinopathy submitted to 1.25 mg of intravitreal bevacizumab injection 3 days before the surgical procedure; (B) Advanced stage of posterior hyaloid detachment in the same case; (C) Endodiathermy at bleeding sites; (D) Use of valved trocars to avoid sudden intraocular pressure changes

neuropathy or diabetic retinopathy; in these eyes, the “safe duration of high IOP” is unknown and should be the lowest one enough to control the bleeding process.

Fluid-Air Exchange Increasing of IOP values can also be achieved by intraocular air/gas application. The surface tension of air bubble is higher than that exerted by fluid. Therefore, an intraocular air/gas bubble frequently stops the blood flow and facilitates thrombus formation.20-22 It is a worldwide surgical technique during extensive hemorrhage because this maneuver is able to maintain the blood “packed” posteriorly to the fluid-air surface, especially at the posterior pole because the surface tension of air is higher than fluid. This is a useful maneuver during extensive bleeding from many causes.20-22 It is also useful during epiretinal membrane and internal limiting membrane peeling, especially in patients unable to stop the systemic anticoagulation therapy due to systemic diseases; in these eyes, bleeding in the macular area is very common and must be treated by indirect compression of the clot using high IOP levels instead of endodiathermy to avoid thermal damage to the macula area. Additionally, in these patients,

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323 bleeding from the iris/ciliary body may occur and should be treated by fluid-air exchange and increasing of the IOP. Vitrectomy systems have an air-pump device for controlled fluid-air exchange. It is suggested that flute, backflush or especially the soft-tipped cannula be used and connected into the vitrectomy aspiration line or preferentially into an accessory extrusion line. The vitrectomy tip can be also used particularly when progression of hemorrhage is too big and results in difficulties for changing the instruments. During the fluid-air exchange, the recently formed little soft clots can be simultaneously removed by aspiration under fluid while the air is injected. Fluid-air exchange may be a good alternative to improve the visualization of the periphery of retina and shows up the bleeding site. It is worthy particularly in cases where vitreous hemorrhage persisted despite adequate blood aspiration. Once bleeding is controlled, reversal from air to fluid state may be done at any moment.

Perfluorocarbon Liquids The properties of transparency, molecular weight higher than water and high surface tension have made PFCLs an adjunctive for management of complicated cases in vitreoretinal surgery.38 Their property of immiscibility with blood and water and its liquid transparency allow surgeons to identify and stop bleeding sites when injected above the retina. This facilitates the hemostasis of bleeding sources. Intraocular perfluorooctane significantly reduced the time to achieve hemostasis.2,38 Injection is performed using a syringe-threaded soft-tipped cannula over the optic disk. To prevent liquid dispersion, the tip must be positioned into the bubble, in order to produce only a big one. Technique for “en bloc” PFCL dissection of fibrovascular membranes in PDR and TRD showed good results in preventing intraoperative bleeding.2 Separation of epiretinal tissues is performed injecting PFCL between retina and posterior hyaloids.2 Additional to iatrogenic retinal breaks that may be observed in 7% of the patients, care must be taken to avoid PFCL injection into subretinal space.2 Moreover, during PFCL injection into the vitreous cavity, the fluid inside the vitreous cavity must go outside of the eye and the valved trocar systems may avoid this fluid migration. For this reason, it is very important to turn off the infusion or insert a needle throughout the trocars; these maneuvers allow the migration of fluid that was displaced by the PFCL through the valved trocars.

Endodiathermy and Cauterization Protein denaturation and hemostasis occur when resistance of tissues to electric currents are applied by diathermy; it is different than cauterization in which an

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324 electric current heat up the probe tip and results in tissue; both techniques— endodiathermy and cauterization—require the touch of the tip of the probe at the target tissue.20-22 Endodiathermy is the preferable technique for many surgeons to manage bleeding during PPV, because it minimizes the epiretinal blood side effects (Figs 3A to D). Unimanual coaxial bipolar endodiathermy probes are available for 20-, 23- and 25-gauge systems. They can be used to coagulate active bleeding retinal neovascularization (Figs 3A to C), which results in an easy dissection of fibrovascular tissue with minimal bleeding and no need to use intraocular forceps/scissors to remove fibrovascular membranes before its segmentation (Figs 3A to C). This procedure is normally followed by endophotocoagulation20-22 (Fig. 3D). It is also useful to assist retinotomies for subretinal fluid drainage. For better control of hemostasis, this technique should be performed using a pedal that contains a progressive control of the intensity. It avoids iatrogenic heating, especially if the bleeding site is close to the fovea or optic disk. In case of inadvertent avulsion of retinal vessel or iatrogenic retinal tears, complementary techniques (e.g. IOP increasing, PFCL, air-fluid exchange) should be used to re-establish visualization and control of bleeding.

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Figures 3A to D  Surgical techniques of endodiathermy for management of intraoperative bleeding. (A) Dissection/segmentation of proliferative tissue in proliferative diabetic retinopathy using 23-gauge vitrectomy probe, 5,000 cuts/ minute, aspiration of 200 mm Hg and 30 mm Hg of infusion pressure; (B) Initial stage of endodiathermy in bleeding sites of proliferative diabetic retinopathy using the diathermy device and the vitreous cutter probe for aspiration; (C) Final stage of endodiathermy in bleeding sites of proliferative diabetic retinopathy using the diathermy device and the vitreous cutter probe for aspiration; (D) Panretinal endophotocoagulation at the final step of proliferative diabetic retinopathy using a flexible/extendable laser probe to avoid the lens touch

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325 Endodiathermy should be avoided at the fovea as well as over the optic nerve and papilomacular bundle (Figs 4A to D). Caution about excessive endodiathermy is very important because it can also result in retinal tears or shortening; in eyes with previous intravitreal anti-VEGF injection, the necessity of excessive endodiathermy is low (Figs 4A to C). At the end of the surgical procedure, fluid-air exchange and intravitreal air or gas injection may be performed to avoid bleeding (Fig. 4D). Elevated disk neovascularization must be treated very carefully with low energy and maximum distance from optic nerve surface to prevent damage to nerve fiber layer and vascular supply.

Laser Photocoagulation Laser energy absorbed by the hemoglobin in the bleeding vessel can induce thermal denaturation of proteins followed by hemostasis, which may be performed under air following a fluid-air exchange to aid in the bleeding

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Figures 4A to D  Intraoperative bleeding control in proliferative diabetic retinopathy using high intraocular pressure and no endodiathermy 3 days following 1.25 mg of intravitreal bevacizumab injection. (A) Initial phase of posterior hyaloid detachment using the vitrectomy probe. The hyaloid is extremely thick and adherent and no bleeding is observed. No additional endodiathermy was necessary; (B) Advanced phase of posterior hyaloid detachment in the same case. No bleeding was detected and no additional endodiathermy was needed; (C) Final surgical step of vitreous base removal to avoid anterior proliferation of proliferative diabetic retinopathy in the same case. Minimal bleeding is observed which was controlled by raising the intraocular pressure for 1–3 minutes. No endodiathermy was necessary; (D) Final aspect of eye at the end of the surgical procedure in the same case after intravitreal air injection

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control.23-25 This may have similar effect to intraocular diathermy. Laser could be initiated using power of 200 mW and exposure time at 200 milliseconds. Delivery should be applied to flat areas and not under direct contact. Laser photocoagulation may be also useful for minimal amount of active bleeding around the attached retina (Figs 5A to D).23-25

Combination of Techniques Alternative instruments with coupled aspiration could be useful in cases of active bleeding. Those aspirating laser probes have practical ability to improve visualization and make local hemostasis without the need to exchange instruments. Nowadays, the combination of techniques for bleeding control and especially the preoperative injection of VEGF inhibitors 3 days before the PPV allows the vitreoretinal surgeon to deal with complex cases (Figs 5 to 7).

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Figures 5A to D  Intraoperative bleeding control in proliferative diabetic retinopathy using several surgical techniques 3 days following 1.25 mg of intravitreal bevacizumab injection and the use of combination of techniques for hemostasis. (A) Complex tractional retinal detachment in a 26-year-old patient; (B) Bimanual dissection and segmentation of proliferative membranes in proliferative diabetic retinopathy following the phacoemulsification/intraocular lens implantation under high intraocular pressure values. Minimal bleeding is observed following previous bevacizumab injection; (C) Fluid-air exchange to reattach the retina and to minimize the bleeding; (D) Panretinal endophotocoagulation after vitreous base removal to avoid anterior proliferation of proliferative diabetic retinopathy followed by silicone oil injection

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A

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Figures 6A to D  Preoperative and postoperative images from eye submitted to intravitreal injection of 1.25 mg of bevacizumab 3 days before the vitrectomy in diabetic tractional retinal detachment. (A) Fluorescein angiogram showing leakage of vessels in macula; (B) Fluorescein angiogram showing leakage in mid-periphery; (C) Infrared image at the 7th postoperative day showing no residual blood at the vitreous cavity. Best corrected visual acuity improved from count fingers at 1 meter to 20/40; (D) Fluorescein angiogram at the 7th postoperative day showing no vitreous bleeding and minimal residual leakage nasal to the optic disk/arcades

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Figures 7A to C  Postoperative images from eye submitted to intravitreal injection of 1.25 mg of bevacizumab followed by phacovitrectomy in the left eye. Best corrected visual acuity improved from hand motion to 20/30. (A) Postoperative infrared image of the left eye at the 30th postoperative day. No residual blood/vitreous is observed; (B) Postoperative composite infrared image showing similar findings; (C) Fluorescein angiogram showing no leakage and no active neovascularization

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Conclusion Intraoperative hemorrhage is frequently observed during PPV in PDR. Vitreoretinal surgeons may be aware regarding the need of preoperative control of systemic disease or risk conditions of intraocular bleeding as well as the choice of surgical tools and techniques that can prevent/treat the intraoperative bleeding during PPV in PDR. The intravitreal injection of 1.25 mg of bevacizumab or 0.5 mg of ranibizumab should be performed around 3 days before all PPV in PDR; this technique decreases the intraoperative bleeding in PDR, optimizing the surgical results. Surgeons must be aware regarding the possibility of worsening previous TRD in complex cases of PDR.

References 1. de Oliveira Dias JR, Rodrigues EB, Maia M, et al. Cytokines in neovascular agerelated macular degeneration: fundamentals of targeted combination therapy. Br J Ophthalmol. 2011;95(12):1631-7. 2. Arevalo JF. En bloc perfluorodissection for tractional retinal detachment in proliferative diabetic retinopathy. Ophthalmology. 2008;115(6):e21-5. 3. Rice TA, Michels RG, Rice EF. Vitrectomy for diabetic traction retinal detachment involving the macula. Am J Ophthalmol. 1983;95(1):22-33. 4. Fong DS, Ferris FL, Davis MD, et al. Causes of severe visual loss in the early treatment diabetic retinopathy study: ETDRS report no. 24. Early Treatment Diabetic Retinopathy Study Research Group. Am J Ophthalmol. 1999;127(2):137-41. 5. Ho T, Smiddy WE, Flynn HW. Vitrectomy in the management of diabetic eye disease. Surv Ophthalmol. 1992;37(3):190-202. 6. Aaberg TM, Abrams GW. Changing indications and techniques for vitrectomy in management of complications of diabetic retinopathy. Ophthalmology. 1987;94(7):775-9. 7. Avery RL, Pearlman J, Pieramici DJ, et al. Intravitreal bevacizumab (Avastin) in the treatment of proliferative diabetic retinopathy. Ophthalmology. 2006;113(10):1695. e1-15. 8. Chen E, Park CH. Use of intravitreal bevacizumab as a preoperative adjunct for tractional retinal detachment repair in severe proliferative diabetic retinopathy. Retina. 2006;26(6):699-700. 9. da R Lucena, Ribeiro JA, Costa RA, et al. Intraoperative bleeding during vitrectomy for diabetic tractional retinal detachment with versus without preoperative intravitreal bevacizumab (IBeTra Study). Br J Ophthalmol. 2009;93(5):688-91. 10. Ishikawa K, Honda S, Tsukahara Y, et al. Preferable use of intravitreal bevacizumab as a pretreatment of vitrectomy for severe proliferative diabetic retinopathy. Eye (Lond). 2009;23(1):108-11. 11. Arevalo JF, Maia M, Flynn HW, et al. Tractional retinal detachment following intravitreal bevacizumab (Avastin) in patients with severe proliferative diabetic retinopathy. Br J Ophthalmol. 2008;92(2), 213-6.

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329 12. Abdelhakim MA, Macky TA, Mansour KA, et al. Bevacizumab (Avastin) as

an adjunct to vitrectomy in the management of severe proliferative diabetic retinopathy: a prospective case series. Ophthalmic Res. 2011;45(1):23-30. 13. Hattori T, Shimada H, Nakashizuka H, et al. Dose of intravitreal bevacizumab (Avastin) used as preoperative adjunct therapy for proliferative diabetic retinopathy. Retina. 2010;30(5):761-4. 14. Zhao LQ, Zhu H, Zhao PQ, et al. A systematic review and meta-analysis of clinical outcomes of vitrectomy with or without intravitreal bevacizumab pretreatment for severe diabetic retinopathy. Br J Ophthalmol. 2011;95(9):1216-22. 15. CATT Research Group, Martin DF, Maguire MG, et al. Ranibizumab and bevacizumab for neovascular age-related macular degeneration. N Engl J Med. 2011;364(20):1897-908. 16. Wu L, Martínez-Castellanos MA, Quiroz-Mercado H, et al. Twelve-month

safety of intravitreal injections of bevacizumab (Avastin): results of the PanAmerican Collaborative Retina Study Group (PACORES). Graefes Arch Clin Exp Ophthalmol. 2008;246(1):81-7.

17. Ribeiro JA, Messias A, de Almeida FP, et al. The effect of intravitreal ranibizumab on intraoperative bleeding during pars plana vitrectomy for diabetic traction retinal detachment. Br J Ophthalmol. 2011;95(9):1337-9. 18. Sanders D, Peyman GA, Fishman G, et al. The toxicity of intravitreal whole blood and hemoglobin. Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1975;197(3):255-67. 19. Ehrenberg M, Thresher RJ, Machemer R. Vitreous hemorrhage nontoxic to retina as a stimulator of glial and fibrous proliferation. Am J Ophthalmol. 1984;97(5):61126. 20. de Bustros S. Intraoperative control of hemorrhage in penetrating ocular injuries. Retina. 1990;10 Suppl 1:S55-8. 21. Ambler JS, Meyers SM. Management of intraretinal metallic foreign bodies without retinopexy in the absence of retinal detachment. Ophthalmology. 1991;98(3):391-4. 22. Chou F, Kertes PJ. Chapter 23: Control of intraocular hemorrhage during vitrectomy. In: Peyman GA, Meffert SA, Conway MD (Eds). Vitreoretinal Surgical Techniques, 2nd edition. Informa Healthcare; 2007. p. 213. 23. Peyman GA, D’Amico DJ, Alturki WA. An endolaser probe with aspiration capability. Arch Ophthalmol. 1992;110(5):718. 24. Chang S. Multifunction endolaser probe. Am J Ophthalmol. 1992;114(5):648-9. 25. Charles S, Chang S, McCuen BW. New techniques for hemostasis during diabetic vitrectomy. Retina. 2003;23(1):120-2. 26. Mason JO, Gupta SR, Compton CJ, et al. Comparison of hemorrhagic complications of warfarin and clopidogrel bisulfate in 25-gauge vitrectomy versus a control group. Ophthalmology. 2011;118(3):543-7. 27. Narendran N, Williamson TH. The effects of aspirin and warfarin therapy on haemorrhage in vitreoretinal surgery. Acta Ophthalmol Scand. 2003;81(1):38-40. 28. Chandra A, Jazayeri F, Williamson TH. Warfarin in vitreoretinal surgery: a case controlled series. Br J Ophthalmol. 2011;95(7):976-8.

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330 29. Oh J, Smiddy WE, Kim SS. Antiplatelet and anticoagulation therapy in vitreoretinal surgery. Am J Ophthalmol. 2011;151(6):934-9. 30. Fu AD, McDonald HR, Williams DF, et al. Anticoagulation with warfarin in vitreoretinal surgery. Retina. 2007;27(3):290-5. 31. Dayani PN, Grand MG. Maintenance of warfarin anticoagulation for patients undergoing vitreoretinal surgery. Arch Ophthalmol. 2006;124(11):1558-65. 32. Brown JS, Mahmoud TH. Anticoagulation and clinically significant postoperative vitreous hemorrhage in diabetic vitrectomy. Retina. 2011;31(10):1983-7. 33. Ishikawa K, Honda S, Tsukahara Y, et al. Preferable use of intravitreal bevacizumab as a pretreatment of vitrectomy for severe proliferative diabetic retinopathy. Eye (Lond). 2009;23(1):108-11. 34. Arevalo JF, Sanchez JG, Saldarriaga L, et al. Retinal detachment after bevacizumab. Ophthalmology. 2011;118(11):2304.e3-7. 35. Heyworth P, Bourke R, Moore C, et al. The systemic absorption of adrenaline from posterior segment infusion during vitreoretinal surgery. Eye (Lond). 1998;12(Pt 6):949-52. 36. O’Brien DM, Farmer SG, Kalina RE, et al. Acute macular neuroretinopathy following intravenous sympathomimetics. Retina.1989;9(4):281-6. 37. Desai UR, Sudhamathi K, Natarajan S. Intravenous epinephrine and acute macular neuroretinopathy. Arch Ophthalmol. 1993;111:1026-7. 38. Moreira Júnior CA, Uscocovich CE, Moreira AT. Experimental studies with perfluoro-octane for hemostasis during vitreoretinal surgery. Retina. 1997;17(6):530-4.

chapter 16

Use of Sustained Drug Release Implants in Vitrectomized Eyes Jose Maria Ruiz-Moreno, Javier A Montero

INTRODUCTION When faced with a patient with macular edema, the first choice therapeutic option is the intravitreal injection of an antiangiogenic or steroid drug. However, in a vitrectomized patient, the practical lack of vitreous gel and its replacement with aqueous humor means a loss of the reservoir capacity of the vitreous cavity. In turn, this will condition the efficacy of such drugs by modifying their pharmacokinetics. This situation normally arises in diabetic patients with diabetic macular edema (DME) who have undergone prior vitrectomy due to proliferative diabetic retinopathy (PDR), although it may also occur in patients with cystoid macular edema following pars plana vitrectomy (PPV) due to a cause other than diabetic retinopathy. Patients with retinal central vein or branch occlusion, as a result of radial optic neurotomy surgery in the former case or dissection of the adventitia in the latter, may also present macular edema. In addition, patients who have undergone PPV for another retinal disease and then develop the neovascular form of age-related macular degeneration (AMD) may also be candidates for intravitreal antiangiogenic treatment. Notwithstanding, as mentioned earlier the most common situation we are likely to find are individuals with PDR who have undergone PPV for persistent vitreous hemorrhage and later present DME requiring intravitreal treatment, as in the clinical case described at the end of this chapter. To date, all double-blind, controlled multicenter trials on the intravitreal use of antivascular endothelial growth factor (VEGF) agents have been conducted in nonvitrectomized eyes.1-5 Accordingly, the real efficacy of these drugs in vitrectomized eyes remains unknown. These eyes show both structural and

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anatomical differences along with varying drug kinetics due to the lack of vitreous gel. What has been established, however, is that surgery in the vitrectomized eye carries a higher risk of complications than in nonvitrectomized eyes.6 However, no study has addressed the issue of possible iatrogenic tears induced in the peripheral retina of vitrectomized eyes by intravitreal injections, so its incidence is so far unknown. Since the anterior chamber is deeper, displacements of the natural lens occur and there is greater zonule weakness. This occurs because of the lack of vitreous support and leads to an increased risk of retinal detachment.6 In addition, in an eye without vitreous support, intravitreal injection could induce possible modifications to the zonula or crystalline lens. In second place, we should consider the changes in the pharmacokinetics of intravitreally administered drugs induced by PPV. The removal of the vitreous gel and its replacement with aqueous humor is beneficial during the course of diabetic retinopathy, since the oxygen supply to the retina is improved and toxic products are more rapidly eliminated. This improvement in vitreous clearance reduces macular edema and neovascularization.7 The improved vitreous clearance in eyes undergoing PPV has also been linked to the elimination of VEGF.8 The authors of this last study, Lee et al observed that following intravitreal VEGF165 injections in rabbits, the half-life of VEGF was tenfold greater in vitrectomized eyes compared to nonvitrectomized eyes.8 In an experimental study performed in macaque monkeys, it was shown that the half-life of intravitreally-injected bevacizumab was reduced by 60% in eyes subjected to PPV compared to nonvitrectomized eyes. Similarly, the reduction in the aqueous humor concentration of VEGF induced by the intravitreal injection of bevacizumab lasted less time in vitrectomized versus nonvitrectomized eyes.9 In human clinical practice, the efficacy of anti-VEGF drugs has been examined in eyes subjected to PPV although results have been contradictory and have depended on the disease treated. Thus, Metha et al10 retrospectively analyzed 60 eyes in which DME was treated by intravitreal bevacizumab and noted worse visual acuity and a diminished reduction in macular thickness in PPV-eyes than nonvitrectomized eyes (P = 0.002 and P = 0.028, respectively). In another retrospective, noncomparative intervention study, visual acuity and foveal thickness were examined in 11 eyes of 10 patients with persistent DME following PPV who were treated with three monthly intravitreal bevacizumab injections of 1.25 mg/0.05 ml. Central foveal thickness was 408±77 mm at baseline, 453±97 mm 3 months after treatment and 454±101 mm at 6 months (P = 0.172). Mean visual acuity was 59±15 (20/80). Early Treatment Diabetic Retinopathy Study (ETDRS) letters at baseline, 59±16 (20/80) at 3 months and 57±15 (20/80) at 6 months (P = 0.398). The authors concluded that no changes were produced in visual acuity or foveal thickness in the short-term attributable to intravitreal bevacizumab in eyes undergoing PPV and removal of the internal limiting membrane.11

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333 In yet another study, Connor found that intravitreal ranibizumab was effective in PPV eyes for the treatment of exudative AMD. In this small noncomparative retrospective study, 10 patients undergoing PPV for different reasons developed exudative AMD at a mean of 5.8 years after vitreous surgery. Mean visual acuity improved from 20/182 to 20/74 following a mean number of 5.6 intravitreal ranibizumab injections.12 These contrasting results should be interpreted with caution since they were obtained in retrospective studies with a limited number of patients. The drugs employed were different (bevacizumab versus ranibizumab), as were the conditions treated (DME versus exudative AMD). It remains unclear whether the increased clearance from the vitreous cavity of anti-VEGF drugs would determine a need for shorter treatment intervals and if this would mean the greater systemic absorption of these drugs with possible repercussions at the general level.13 From a theoretical standpoint, the greater rate of elimination of the anti-VEGF drug from the vitreous cavity would mean a lowered efficacy. This problem could be resolved by the use of a sustained release implant to achieve longer-lasting concentrations of the drug. The Ozurdex implant by Allergan for the treatment of macular edema in vein occlusions14 achieves the sustained release of dexamethasone and may therefore be useful in vitrectomized eyes. In the Champlain study,15 the authors assessed the safety and efficacy of the dexamethasone implant for the treatment of DME in PPV eyes. In this multicenter, prospective trial of 26 weeks’ duration, 55 patients received a single injection of the 0.7 mg dexamethasone implant (Ozurdex, Allergan). The main outcome measure was the change in OCT-determined central foveal thickness produced at 26 weeks. Mean patient age was 62 years and mean DME duration was 43 months. The mean central foveal reduction produced was –156 μm (–190 to 122 μm) at 8 weeks (P < 0.001) and –39 μm (–65 to 13 μm) at 26 weeks (P = 0.004). Mean visual acuity was improved from 54.6 ETDRS letters, by 6 letters (3.9–8.1) at 8 weeks (P < 0.001) and by 3.0 letters (0.1–6.0) at 26 weeks (P = 0.046). The main adverse effect was an increase in intraocular pressure. The authors concluded that the sustained release implants led to significantly improved vision and DME in vitrectomized eyes, with an acceptable safety profile.15 According to the available information, the first choice for the treatment of macular edema in eyes previously subjected to PPV would be the intravitreal injection of a sustained release implant containing steroids. For PPV eyes with exudative AMD, the real efficiency of intravitreal treatment with antiangiogenics is yet to be determined. Future studies need to address the possibility of treatment with antiangiogenic drugs alone or in combination with the intravitreal injection of a sustained steroid releasing device.

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CLINICAL CASE A 58-year-old man with a history of diabetic retinopathy treated with panretinal photocoagulation in both eyes presented with bilateral traction retinal detachment and PPV was performed in both eyes. Two years later he underwent cataract surgery and showed a best corrected visual acuity of 20/32 in the right eye and 20/25 in the left eye. At 17 months postcataract surgery, the patient suffered a loss of vision in the RE (20/160) due to the development of DME (Figs 1A and B). Given his prior PPV, an intravitreal Ozurdex® implant was used. One month later, normal foveal anatomy was recovered and the DME had resolved (Figs 2A and B). At 3 months, visual acuity had improved to 20/40 and there was no DME (Fig. 3); the intravitreal implant was visible in the inferior zone of the vitreous cavity (Fig. 4).

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Figures 1A and B (A) 58-year-old man, who had undergone prior vitrectomy and cataract surgery, presenting with diabetic macular edema; (B) Appearance of the fundus in the same patient

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Figures 2A and B (A) Normal foveal anatomy observed 1 month after placement of the Ozurdex® implant; (B) Appearance of the fundus post-treatment

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Figure 3

Visual acuity was 20/40 at 3 months post-treatment. Note the absence of macular edema

Figure 4

Vitreous implant visible in the inferior zone of the vitreous cavity

REFERENCES 1. Rosenfeld PJ, Brown DM, Heier JS, et al. Ranibizumab for neovascular age-related macular degeneration. N Engl J Med. 2006;355(14):1419-31. 2. Brown DM, Kaiser PK, Michels M, et al. Ranibizumab versus verteporfin for neovascular age-related macular degeneration. N Engl J Med. 2006;355(14):1432-44. 3. Elman MJ, Bressler NM, Qin H, et al. Expanded 2-year follow-up of ranibizumab plus prompt or deferred laser or triamcinolone plus prompt laser for diabetic macular edema. Ophthalmology. 2011;118(4):609-14. 4. Brown DM, Campochiaro PA, Singh RP, et al. Ranibizumab for macular edema following central retinal vein occlusion: six-month primary end point results of a phase III study. Ophthalmology. 2010;117(6):1124-33. 5. Campochiaro PA, Heier JS, Feiner L, et al. Ranibizumab for macular edema following branch retinal vein occlusion: six-month primary end point results of a phase III study. Ophthalmology. 2010;117(6):1102-12. 6. Shousha MA, Yoo SH. Cataract surgery after pars plana vitrectomy. Curr Opin Ophthalmol. 2010;21(1):45-9. 7. Stefánsson E. Physiology of vitreous surgery. Graefes Arch Clin Exp Ophthalmol. 2009;247(2):147-63. 8. Lee SS, Ghosn C, Yu Z, et al. Vitreous VEGF clearance is increased after vitrectomy. Invest Ophthalmol Vis Sci. 2010;51(4):2135-8.

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336 9. Kakinoki M, Miyake T, Sawada O, et al. The clearance of intravitreal bevacizumab in vitrectomized macaque eyes. Poster presented at: Annual meeting of the Association for Research in Vision and Ophthalmology; Fort Lauderdale, FL;May 5,2011. 10. Mehta S, Blinder KJ, Shah GK, et al. Intravitreal bevacizumab for the treatment of refractory diabetic macular edema. Ophthalmic Surg Lasers Imaging. 2010;41(3):323-9. 11. Yanyali A, Aytug B, Horozoglu F, et al. Bevacizumab (Avastin) for diabetic macular edema in previously vitrectomized eyes. Am J Ophthalmol. 2007;144(1):124-6. 12. Helzner J. Lucentis in vitrectomized eyes. Retinal Physician. 2010;7:8. 13. Waisbourd M, Loewestein A. Anti-VEGF therapy in vitrectomized eyes. Retinal Physician. 2011;8:40-1. 14. Haller JA, Bandello F, Belfort R, et al. Randomized, sham-controlled trial of dexamethasone intravitreal implant in patients with macular edema due to retinal vein occlusion. Ophthalmology. 2010;117(6):1134-46. 15. Boyer DS, Faber D, Gupta S, et al. Dexamethasone intravitreal implant for treatment of diabetic macular edema in vitrectomized patients. Retina. 2011;31(5):915-23.

chapter 17

Enzymatic Vitrectomy Patricia Udaondo, David Salom, Salvador Garcia-Delpech, Manuel Díaz-Llopis

INTRODUCTION The vitreous is an extracellular matrix of a spherical shape that fills the center of the eye with a transparent gel that maintains clarity and protects the internal structures from the eye, head and body movements. In terms of the molecular components, 99% of the composition of the vitreous is water and its main structure is formed by a matrix of hyaluronic acid surrounded by collagen fibrils and little content cell that makes it ideal for handling pharmacological manipulation.1 The relationship and ratio of its main components (water/collagenhyaluronic acid) is conferred to the vitreous structure; the central vitreous is less dense than the cortex by presenting less collagen and hyaluronic acid and more water. This difference becomes more apparent with age because of the progression of the liquefaction of the central vitreous with time.2 The problem is that these changes are not symmetric in the vitreous cavity which leads to a liquefaction and an abnormal separation of the posterior vitreous. This process is believed to be associated with the pathogenesis of various vitreoretinal pathologies (concept of asynchronous aging by Sebag).3 In recent years, the importance of the vitreous and the vitreoretinal interface in the pathogenesis of many diseases of the posterior pole has increased and the treatment thereof, mainly with surgical modalities. The side effects of the persistence of a strong adherence of the vitreous to the retina (pathology of the vitreoretinal interface) and, on the other hand, the benefits of its slow and controlled detachment from the retina are already well known. Among the side effects we find: ƒƒ Recurrence of retinal detachment with or without vitreoretinal proliferation and appearance of retinal tears ƒƒ Persistency, chronicity and exacerbation of macular edema (diabetic , vein occlusion, uveitis, pseudophakic) (Fig. 1)

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338 ƒƒ Vitreoretinal traction syndrome: macular holes or epiretinal membranes

among others (Figs 2 and 3) ƒƒ Progression of retinal neovascularization, mainly in diabetic retinopathy ƒƒ Higher risk of development or appearance of wet age-related macular

degeneration.

Figure 1 Optical coherence tomography image showing a large macular edema refractory to intravitreal treatment. Note the epiretinal membrane associated and the posterior hyaloid attached. Both are considered the cause of this diabetic macular edema

Figure 2

Figure 3

Optical coherence tomography showing an epiretinal membrane with the posterior hyaloid detached

Vitreoretinal traction syndrome in optical coherence tomography

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CONCEPT OF ENZYMATIC VITRECTOMY The enzymatic or pharmacological vitreolysis/vitrectomy is the therapy that tries to break the vitreous structure in small particles and get its liquefaction to weaken its retinal adhesion and finally obtain a subsequent complete and safe detachment of the vitreous.4 It includes all the mechanical and biochemical changes resulting from the pharmacological manipulation of the vitreous. Over time and through various studies, it has been demonstrated that the vitreous detachment is a dynamic process that involves many enzymatic reactions; Trese encompasses all of these chemical and molecular changes in the term vitreodynamics.5

METHODS AND MECHANISM OF ACTION Although the concept of pharmacological vitrectomy is resuming force at present it is not a new concept. A good example of this is the work done by Professor Alió in the 1980s with the intravitreal injection of hyaluronidase.6 many substances have been tested with variable degrees of success, to handle pharmacologically the vitreous. Among them we highlight: ƒƒ Hyaluronidase: It is an enzyme which digests the proteoglycans. The last commercial hyaluronidase that has been tested is the purified ovine hyaluronidase (Vitrase®) that has demonstrated its effectiveness in the management of vitreous hemorrhages by liquefying the vitreous but does not detach the vitreous ƒƒ Collagenases: They are a group of enzymes that degrade the collagen. There are up to 18 types being the most important the collagenase II (C1764 Sigma, St. Louis, missouri) but its function is still unclear ƒƒ microplasmin [Ocriplasmin ® (Thrombogenics Ltd, Dublin)]: It is a recombinant human plasmin. The results of the trials in phase III related to the treatment of macular holes already have been published and it has demonstrated its effectiveness in the detachment of the vitreous7 ƒƒ Autologous plasmin purified or in its simplified form: It is a serum human protease. The main action of plasmin and microplasmin is to act or trigger the fibrinolysis. Inside the eye it has a proteolytic activity against laminin and fibronectin that are responsible for maintaining the adherence of the vitreous to the surface of the retina; this is the reason why it is considered an inducing agent of the posterior detachment of the vitreous.8 As mentioned previously, the vitreous detachment also causes an increase of retinal oxygenation as well as the modification of some molecules like cytokines and growth factors in the vitreous cavity which could explain the anti-inflammatory and antiangiogenic action of autologous plasmin and so its many indications among which we highlight: ƒƒ Adjuvant of surgery: his best known indication. Radically reduces surgical time in macular holes, retinopathy of prematurity and diabetic retinopathy9,10 (Fig. 4)

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340 ƒƒ Vitreoretinal traction syndrome:11 Including epiretinal membranes and

macular holes (Figs 5 to 7)

ƒƒ Macular edema: diabetes, vein occlusion, uveitis, pseudophakic12-14 (Fig. 8).

Regarding the security profile of both autologous plasmin and microplasmin is good, being less frequent the side effects associated with autologous plasmin compared to microplasmin. It has been described, associated with microplasmin, some cases of peripheral retinal tear and vitreous hemorrhage; it is believed that those effects are dose dependent.7

Figure 4 Image of a patient with an epiretinal membrane. This patient was treated with a single injection of autologous plasmin and pars plana vitrectomy. The relevance of the case is that the membrane was not peeled but it was aspirated during vitrectomy (Membrane lysis)

Figure 5 Optical coherence tomography image of a patient with an epiretinal membrane before and after the treatment with three intravitreal injections of autologous plasmin separated by 1 month. The only place where the membrane is still attached is the optic nerve and the macula appears free

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Figures 6A and B (A) Another patient with an epiretinal membrane treated with three injections of autologous plasmin; (B) The membrane has disappeared after the therapy

Figure 7 Optical coherence tomography image corresponding to a patient with vitreomacular traction treated with intravitreal autologous plasmin

Figure 8 Patient showing a refractory diabetic macular edema treated with autologous plasmin. We can observe how the maximum edema is where the posterior hyaloid is attached to the retina and how the edema improves when the hyaloid is detached after the treatment

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REFERENCES 1. Sebag J, Balazs EA. Morphology and ultrastructure of human vitreous fibers. Invest Ophthalmol Vis Sci. 1989;30(8):1867-71. 2. Sebag J. Structure, function and age-related changes of the human vitreous. In: Schepens CL, Neetens A. The vitreous and vitreoretinal interface. New York: Springer-Verlag; 1987:20. p. 17. 3. Sebag J. Macromolecular structure of vitreous. Progr Polym Sci. 1998;23:415-46. 4. Gandorfer A. Pharmacologic vitreolysis. Dev Ophthalmol. 2007;39:149-56. 5. Quiram PA, Leverenz VR, Baker RM, et al. Microplasmin-induced posterior vitreous detachment affects vitreous oxygen levels. Retina. 2007;27(8):1090-6. 6. Alió J, Sanchez A, Ludeña MD, et al. Vitreolisis enzimática: Estudio experimental de un nuevo método no mecánico de vitrectomia. Arch Soc Esp Oftal. 1987;53:349-60. 7. de Smet MD, Gandorfer A, Stalmans P, et al. Microplasmin intravitreal administration in patients with vitreomacular traction scheduled for vitrectomy: the MIVI I trial. Ophthalmology. 2009;116(7):1349-55. 8. Li X, Shi X, Fan J. Posterior vitreous detachment with plasmin in the isolated human eye. Graefes Arch Clin Exp Ophthalmol. 2002;240(1):56-62. 9. Sakuma T, Takana M, Inoue J, et al. Efficacy of autologous plasmin for idiopathic macular hole surgery. Eur J Ophthalmol. 2005;15(6):787-94. 10. Williams JG, Trese MT, Williams GA, et al. Autologous plasmin enzyme in the surgical management of diabetic retinopathy. Ophthalmology. 2001;108(10):1902-5. 11. díaz-Llopis m, Udaondo P, Cervera E, et al. Enzymatic vitrectomy by intravitreal autologous plasmin injection as initial treatment for macular epiretinal membranes and vitreomacular traction syndrome. Arch Soc Esp Oftalmol. 2009;84(2):91-100. 12. díaz-Llopis m, Udaondo P, García-delpech S, et al. Enzymatic vitrectomy by intravitreal autologous plasmin injection, as initial treatment for diffuse diabetic macular edema. Arch Soc Esp Oftalmol. 2008;83(2):77-84. 13. Diaz-Llopis M, Udaondo P, Arevalo F, et al. Intravitreal plasmin without associated vitrectomy as a treatment for refractory diabetic macular edema. J Ocul Pharmacol Ther. 2009;25(4):379-84. 14. Udaondo P, diaz-Llopis m, Garcia-delpech S, et al. Intravitreal plasmin without vitrectomy for macular edema secondary to branch retinal vein occlusion. Arch Ophthalmol. 2011;129(3):283-7.

chapter 18

Posterior Vitrectomy Complications Carme Guardia, Jaume Catalá, Jairo Hoyos-Chacón

INTRODUCTION The advancement of surgical techniques has improved the outcome of surgery in the treatment of vitreoretinal pathologies. Surgical results depend on multiple factors and one of them is the ability of the surgeon to reach the objectives of the surgery whether or not intraoperative and/or postoperative complications exist. In this chapter we will focus on the description, and treatment of different complications if they occur, and the analysis of how to avoid them.

INTRAOPERATIVE COMPLICATIONS Sclerotomy Complications Sclerotomies must be placed in the pars plana before the ora serrata. The election of the correct placement of the sclerotomy at 3–3.5 mm in aphakic/ pseudophakic eyes and at 4 mm in phakic eyes, with a distance of about 160° between the light probe and the vitreotome is fundamental to work easily along different areas of the retina during vitrectomy and to have access to the peripheral retina without crossing the instruments behind the crystalline lens.1 If the sclerotomy is at 3 mm, we can access up to 6.5 mm from the opposite side of the ora serrata without touching the crystalline lens. While, if the sclerotomy is placed at 4 mm we can reach up to 3.1 mm. If the sclerotomies are placed at 3 mm, we can move the instrument for 2.8 hours and reach the ora serrata without touching the periphery of the crystalline lens, while if the sclerotomy is at 4 mm from the limbus, the time span stretches to 3.8 hours.2

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Placement of the Infusion Cannula The sclerotomy corresponding to the infusion cannula, is the first that must be performed and we must take into account that in eyes with anterior proliferative vitreoretinopathy (PVR), choroidal detachments, anterior traumas or dense vitreous hemorrhage, the infusion cannula may be incorrectly placed, and in the case of opening the passage of fluid without having correctly checked that the cannula of infusion was inside the vitreous cavity, can cause serious complications. To avoid them it is best to make sure it is on vitreous chamber by direct observation illuminating it from outside the eye with an intraocular light: ƒ Uveal infusion: This happens when the infusion cannula does not get through all the pigmented pars plana epithelium. While the vitrectomy is in progress, the infusion in the suprachoroidal space increases, flattening of the anterior chamber due to a forward shift of the vitreous and the ciliary body. Early diagnosis and closing the infusion immediately are very important. The main goals of the treatment are to restore the vitreous volume and try to drain the suprachoroidal fluid. Remove the infusion cannula and connect it to a 30-gauge needle that is introduced through the pars plana (if there is enough room), through the limbus (in aphakics) or through the anterior chamber even in phakics.3 ƒ Subretinal infusion: This can happen in eyes with retinal detachment (RD) associated with the pars plana when the infusion cannula does not get through completely. This complication must be suspected when RD increases at a fast rate during the course of the vitrectomy.3 When this situation arises, the infusion must be closed immediately, and we must try to restore the vitreous volume with the infusion line connected to a needle, as in the former case. After this, try again to pierce completely the pars plana with a 6 mm cannula, or try to place the infusion through another sclerotomy in a new position. These two complications should be prevented by making sure the infusion cannula extremity is always in the vitreous cavity before opening the passage of fluid (Fig. 1). When in doubt, if we see some tissue on the extremity of the cannula, we can enter through a sclerotomy with a 20-gauge needle with infusion while the assistant lights with a light pipe through the pupil. Indenting the cannula, we can cut the tissue that obstructs the extremity avoiding a crystalline lens injury in phakic patients.4 Another option is to use a longer (6 mm) infusion cannula from the beginning in those cases where complications in reaching the vitreous cavity are foreseen. In these cases, we must take care not to produce an anterior deflexion, which could cause a touch to the crystalline lens, or a posterior deflexion, which could cause a peripheric iatrogenic break in the infusion meridian, especially if we have placed a circumferential band and we are working with an air-filled eye.

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Vitreous or Retinal Incarceration Vitreous incarceration in sclerotomy is inevitable and is a frequent cause of peripheric iatrogenic breaks. In diabetic patients the incarcerated vitreous can offer support to neovascular proliferation which gives rise to repetitive vitreous hemorrhages in the late postsurgical period. We must try to minimize this complication by separating the vitreous from the entry sclerotomies, attempting not to remove the instruments while we are working at high pressure and extracting the incarcerated vitreous with the vitreotome. The retinal incarceration at the sclerotomy level is a serious complication which follows vitreous incarceration in eyes with very bullous RDs. Treatment must try to decrease retinal prolapse estimating the performance of air exchange.5 If the prolapse does not decrease, we must try with a blunt instrument, or an injection of viscoelastic agents while injecting perfluorocarbon liquid (PFCL) into the posterior pole. This complication can be avoided by introducing and removing the instruments carefully, slowing or even closing the passage of infusion before exiting the eye and stabilizing the retina with PFCL if there is significantly bullous RD.3

Hemorrhage Sclerotomies can cause bleeding not only during surgery but also during the postoperative period. In order to avoid this, it is very important to perform a correct diathermy of the superficial blood vessels and to prevent hypotony through the end of the surgical procedure. If bleeding occurs, a diathermy with conic tip can help us to stop it. The introduction of a sharp instrument must be done carefully so as to avoid enlarging the sclerotomy and the possibility of a secondary hemorrhage (Fig. 2).

Figure 1 Maneuver to check that the infusion cannula is inside the vitreous cavity: with the microscope light off, indent the infusion while placing the light probe in limbus until the metallic shine of the cannula tip can be seen

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Figure 2

Sclerotomy enlargement introducing a barbed microvitreoretinal blade used as a pick

Retinal Tears This subject will be covered in part 3, which covers anterior iatrogenic retinal tears.

VISUALIZATION PROBLEMS Visualization problems are very frequent and the prevention and proper treatment can avoid more complications associated with bad visualization.

Corneal Complications The most frequent intraoperative corneal complications are epithelial defects, epithelial corneal edema and Descemet membrane-endothelium folds. They can appear in any patient but are more common in diabetics, who can often have fewer adherences between the corneal epithelium and the Bowman’s membrane. For this reason, diabetic patient’s cornea is very vulnerable to trauma and moisturization changes (Figs 3A and B). In these patients, prevention is possible with the use of topical autologous serum 1 week before vitrectomy.6 The corneal epithelium must be protected from desiccation and trauma during the course of the entire surgical procedure as well as during preparation with 2% methylcellulose. Epithelial defects can be caused by small traumas as well as by extended traumas such as contact lens use. In some rare occasions they are so great as to impair fundus visualization. Epithelial corneal edema appears when ocular pressure remains elevated and is related to surgery length. A polished phacoemulsification and lensectomy technique is important, reducing the time and duration of ultrasounds. We must try to improve corneal conditions by diminishing infusion pressure and using corneal dehydration maneuvers with absorbent sponges (Fig. 4). The last resource is corneal de-epithelialization.

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A

B

Figures 3A and B (A) Epithelial bullae during phacoemulsification prior to posterior vitrectomy in a diabetic patient with vitreous hemorrhage; (B) Acceptable visualization is maintained during surgery

Figure 4

Corneal dehydration maneuver with absorbent sponges to improve visualization through the edematous epithelium

Descemet membrane-endothelium folds occur in aphakic patients when the air exchange is performed or when there are variations in ocular tension and excessive intraocular maneuvers. Descemet membrane folds will disappear if methylcellulose is injected via pars plana into the anterior chamber while working in an air-filled eye.

Myosis Wide-angle viewing systems have decreased the need to work with large pupils. In cases where it is necessary to work comfortably on the vitreous base we will use the systems described in chapter 5. To maintain mydriasis during surgery it may be diluted with adrenaline 1:1,000 in the infusion serum. Myosis can occur intraoperatively as a consequence of long surgical procedures, manipulations of the iris during combined anterior segment surgeries, and during situations that generate episodes of hypotony. If the myosis persists and makes surgical procedure difficult we can resort to different pupil dilatation techniques according to the patient being phakic, aphakic or pseudophakic (Table 1).

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348 TABLE 1 Pupil dilatation techniques Phakic

• Viscoelastics • Translimbal iris hooks (6 a)

Aphakic

• Iris hooks • Iris sutures (6 b) • Sphincterotomies and iridectomies

Pseudophakic

• Viscoelastics • Iris hooks • Iris sutures

B

A

Figures 5A and B

Mydriasis obtained by retractors and iris sutures

In current practice, if sodium hyaluronate is not enough to achieve an adequate mydriasis, we should resort to iris hooks, and only in the case that these hooks are unavailable, we should consider other options (Figs 5A and B). The use of iris hooks can cause tears in the sphincter resulting in permanent mydriasis and small hemorrhages. Hooks can become loose if they have been reused and some infusion may leak through the paracentesis.

Cataract Cataracts can cause visualization problems which affect the safety of the surgical procedure. Although wide visualization field systems help to improve visualization, when a patient who needs vitreoretinal surgery has a cataract, it is currently preferred to perform a combined surgical procedure to reduce the number of surgeries and accelerate visual rehabilitation. On the other hand, it is well known that posterior vitrectomy favors the progression of pre-existent opacities. Various options are currently available when a combined cataract and posterior vitrectomy surgery is required: ƒƒ Lensectomy ƒƒ Phacoemulsification and intraocular lens (IOL) in the capsular bag ƒƒ Lensectomy preserving the anterior capsule +/- IOL in the sulcus.

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349 In our opinion, the preferred technique is phacoemulsification previous to posterior vitrectomy using the technique described in chapter 5, pointing out that, in order to avoid complications, a good surgical technique is critical to prevent iris manipulations which favor myosis and corneal alterations. This technique also offers the advantage of being able to decide when to implant the lens, having the lens inside the sac and preserving the integrity of the zonulocapsular barrier. If lensectomy via pars plana is indicated, we will have an advantage in visualization, but visual rehabilitation will be more difficult, and there is the potential risk of luxation of crystalline lens fragments into the vitreous cavity. Lensectomy preserving the anterior capsule or Blankenship technique7,8 can be used in complex vitreoretinal pathologies and offers the advantages of preventing gas or silicone oil related intra- and postoperative complications, allowing to decide whether or not the lens should be implanted, and maintaining the normal appearance of the iris. It must be considered that there is also a risk of luxation of crystalline lens fragments and the IOL must be implanted in sulcus. This surgical technique consists of fragmenting the crystalline lens via pars plana and polishing the posterior surface epithelium of the anterior capsule. After this, continue with the vitrectomy and peripheral retina work. At the end of the surgery it must be decided whether or not the lens is implanted in sulcus. If we are interested in preserving the integrity of the zonulocapsular barrier, we can postpone the capsulotomy; otherwise, perform a capsulotomy via pars plana with the vitreotome. In rare occasions, a very hard cataract must be extracted through a limbic incision performing an extracapsular surgery. In these cases, we must try not to manipulate the iris, check that the surgical incision is tight by increasing infusion pressure, and thereby avoid leaks and complications during the vitrectomy. It will also be useful to avoid the use of rings sutured either by noncontact visualization techniques or with silicone rings. Injury to the crystalline lens during vitrectomy generally occurs during maneuvers to separate the peripheric vitreous from the opposite side. To avoid this injury, it is fundamental to choose correctly the distance of the sclerotomies from the limbus and the sclerotomy meridian (2–10 hours) 160° apart2 and to use peripheral indentation. Changing hands of the vitreotome enable access to the vitreous base without having to cross the instruments behind the crystalline lens. Curved instruments, such as laser probes and vitreotomes, allow access to the peripheral retina with a lesser chance than straight instruments of injuring the crystalline lens.9 If major injury is produced during the vitrectomy, normally a cataract is rapidly developed which opacifies the entire crystalline lens within a few days. In these cases, the best option is to implant the IOL in the same surgical intervention, performing a Blankenship lensectomy. If there is a slight touch and the posterior crystalline capsule has not been torn, we can see the evolution of the opacity (Fig. 6). Crystalline lenses in young people present a great recovery capacity, but in older patients, the cataract will tend to progress.

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Figure 6

Vitreotome cutter lens injury that develops cataract in the postoperative period

Intraocular Lens Complications The most common complication associated with IOLs during vitrectomy is difficult visualization, especially when working in an air-filled eye. The desiccation produced in the posterior capsule reduces visibility and improves by injecting a small amount of methylcellulose through the pars plana. For deposits of various materials (anti-inflammatories, hematics, and fibrin) or air bubbles that limit vision, we should attempt cleansing and suction through a limbic paracentesis, or injecting viscoelastic. When silicone oil comes into contact with a silicone IOL, the silicone oil irreversibly coats the lens and obscures both the view in and the view out. The silicone coating is very adherent and cannot be dislodged by instruments or viscoelastics. When the use of silicone oil is contemplated in an eye with a silicone IOL and posterior capsulotomy, we must either consider removing the lens or using a long-acting gas instead. Intraocular lens can get shifted or dislocated if there is insufficient support during manipulations of the eye while implanting a scleral procedure, especially if the eye is filled with air or is hypotonic. If the IOL cannot be repositioned, it is important to complete the peripheral vitrectomy before manipulating it so as to minimize traction over the vitreous gel which could cause peripheral tears. Then, it should be assessed, in each case, whether it is better to explant the lens or to anchor it with a fixation suture.

Hemorrhage The intraoperative bleeding is a common problem during vitreoretinal surgery, but fortunately, in most cases it is solved with simple maneuvers.10 Hemorrhages are especially frequent during proliferative diabetic retinopathy (PDR) vitrectomies and depend on the degree of the proliferation’s activity extension as well as the presence of neovessels in the iris (Fig. 7). Other factors that have an influence on bleeding and that must be previously assessed are the patient’s vascular state, the presence of arterial hypertension, nephropathy and

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Figure 7

Bleeding of iris neovessels can form a thin hematic layer which makes visualization difficult

the diabetes mellitus control. Patients with previous panphotocoagulation will tend to bleed less. The use of anti-VEGF injections before vitrectomy reduces the bleed, although the risk of tractional RD increases.11 Hemorrhage can occur as a result of retinal tears and vascular avulsions, which can be prevented with careful surgical technique. Choroidal hemorrhage is a rare but particularly serious complication, and some of the risk factors associated with it are: elderly patients, increase of preoperative eye pressure, RD, aphakia or pseudophakia, and the association of a scleral procedure.12 It can be said that there are no untreatable hemorrhages. We must try to block blood from going under the retina. The initial treatment consists of increasing infusion pressure until the bleeding stops. We must take into account that this strategy will only be effective if the system is well sealed either by the instruments or with plugs. Removing the instruments while eye pressure is high will result in vitreous incarceration, possible retinal tears and even retinal incarceration if the retina is detached. Another possibility is to raise the level of the infusion ampoule, but we must know how to calculate the pressure we are putting the eye under (see chapter 4). After a few minutes, the eye pressure must be lowered, and if bleeding resumes, we can try to treat the point of bleeding (generally neovessels) by using a conic tip diathermy, backflush diathermy systems or tissue manipulator. There are illuminating laser probes that can be used to coagulate precisely a bleeding point while blood is vacuumed with a suction line or vitreotome.13 Laser probes with aspiration capability are useful in cases of active bleeding.14 If bleeding persists, direct pressure on the bleeding point should be attempted with a silicone tip suction cannula or other instruments designed to stop the hemorrhage of the injured vessel and achieve clot formation.15 If the vitreous cavity is filled with blood, performing air exchange will concentrate all the blood in the posterior pole, allowing its suction and improving visualization of the bleeding point, and enabling work on the same. When hemostasis is reached, infusion pressure is gradually diminished and the passage of fluid is opened.

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352 Bovine thrombin, a powerful hemostatic agent, combined with the infusion fluid, accelerates the process of clotting. Its use is limited by the inflammation it produces, but can be prescribed in cases of profuse and difficult control bleeding.16,17 Viscodelamination is a useful surgical technique to ease dissection of very vascularized proliferations in the treatment of diabetic retinopathy.18 Preoperative hemorrhage prophylaxis begins by assessing not only local situations (such as iris neovessels, fibrovascular proliferations, etc.) but also systemic ones, which can favor the hemorrhage, and by trying to improve them, if it is possible. These norms are useful to follow during surgical procedure: ƒƒ Avoid situations of prolonged eye hypotony which favor bleeding ƒƒ In potentially bleeding situations, such as when segmenting very vascular proliferations, increase eye pressure or treat prophylactically with diathermy ƒƒ Use careful surgical technique to avoid iatrogeny, which can cause tears or vascular avulsions that generate bleeding ƒƒ Careful scleral surgery to avoid iatrogeny (scleral perforation during suture placing). Adjust the band at the end of surgery ƒƒ Correct diathermy of sclerotomies, at times a conic tip diathermy can be useful.

Retinal Tears Iatrogenic retinal tears19 are a frequent and serious complication of vitreoretinal surgery, varying in incidence from 4–30%, depending on the type of indication. If they are not diagnosed and treated correctly, they can result in RD with severe diminution of visual acuity and require additional surgery.

Anterior Retinal Iatrogenic Tears These are caused by the entry, and especially, the removal of instruments from the eye. Any instrument can produce them, but in most cases, they are generated by those with edges where the vitreous can get caught, such as scissors (especially right-angle vertically cutting scissors) which generate a pushing movement when entering, or a traction movement when withdrawn on the posterior edge of the vitreous base that causes the tear. We will look for these tears on the sclerectomy meridians and, most frequently, in the sclerotomy of the dominant hand.19 Other less common mechanisms which can generate these kinds of tears are: (a) external traction of the incarcerated vitreous in the sclerotomy with tweezers, for example, when removing the sclerotomy plug; (b) direct injury or cut with the vitreotome or other instruments; (c) hyaloid separation maneuvers with peripheral vitreous traction; (d) internal traction of the peripheral vitreous during, for example, the dissection of an adhered posterior hyaloid; (e) scleral perforation during fixation sutures in case of combined scleral surgery.

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353 Prevention is essential in order to avoid these kinds of tears: ƒƒ Gently introduce the instrument through the sclerotomy and minimize entries and removals ƒƒ Visualize the entry of instruments, and in case of vitreous traction, proceed to change the direction of entry ƒƒ Clean the incarcerated vitreous with the vitreotome in sclerotomies. Avoid tractions of the vitreous ƒƒ Try not to work with eye pressures higher than 25–30 mm Hg which favor vitreous incarceration ƒƒ Always revise the entire peripheral retina with indentation before performing air exchange and at the end of surgery in order to do an early diagnosis. Treatment consists, first, of releasing vitreous tractions on the tear and cleaning the vitreous incarcerated in sclerotomy, if present. Then perform a retinopexy procedure, leaving a short-acting gas or air inside the eye, and positioning the patient in the correct manner (Fig. 8). In case there is pathology of the vitreous base, the association of a scleral indentation buckle would be indicated.

Posterior Retinal Iatrogenic Tears These can be produced by direct injury caused by the instruments or by traction of the vitreous or membranes. They are frequent in delamination and segmentation maneuvers on diabetic patients.20 They can also occur on the edge of laser impacts and in areas of atrophic retina. Prevention is performed by controlling the position of the instruments during the entire procedure and avoiding traction over proliferations and epicenters.

Figure 8 Anterior iatrogenic retinal tear during proliferative diabetic retinopathy vitrectomy. We must specially take care to relieve all vitreous tractions arrow the tear and isolate fibrovascular proliferations

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354 In case of tears in diabetic patients, a total extraction of proliferative tissue is required, followed by an exchange of liquid by air to accomplish the reapplication of the retina, and finally laser application around the tear and substitution for long-acting gas.

Retinopexy Complications Endolaser The endolaser is used to treat retinal tears and to perform panretinal photocoagulations, and in certain occasions, to coagulate bleeding vessels. Complications are related to very intensive treatments or direct trauma to the retina by the probe. The risk of hemorrhage with injury to the Bruch’s membrane (which produces a “popping” sound) diminishes using low power and long exposure burns. We must employ the least intensity which can accomplish the appropriate effect, changing parameters according to the degree of eye pigmentation, especially if laser is performed in an air-or gas-filled eye, since in these media the effects of the laser intensify. Avoid treating areas with retinal hemorrhage, which absorb the laser’s energy.

Cryotherapy This is the preferred method to treat small holes and to finish peripheral retina ablation. The cryoprobe can be used as indentator during periphery revision at the end of surgery. Cryotherapy generates inflammation and dispersion of viable retinal pigment epithelium (RPE) cells when there are retinal tears.21 These two elements combined, if administered in excess, favor PVR not only in predisposed eyes but also in those where no risk factors are present. As a system of retinopexy, endophotocoagulation is generally preferred, but in case of needing cryotherapy, we must know how to use it well: (a) limit to a minimum the number and time of the applications, (b) avoid treating exposed RPE areas, (c) avoid refreezing areas already treated, (d) avoid prophylactic or diagnostic cryotherapy, and (e) wash postcryotherapy RPE dispersed cells by performing an air-fluid exchange.

POSTOPERATIVE COMPLICATIONS Corneal Complications Epithelial defects are seldom very painful and heal quickly except in diabetic patients and in previous corneal diseases22 (Fig. 9). While epithelial defects heal, folds in the Descemet membrane or corneal edema can arise, which will make fundus visualization difficult.

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Figure 9

Postvitrectomy epithelial defect in a diabetic patient

Prevention starts using topic autologous serum in risk patients; in the operation room, protecting the corneal epithelium from dehydration and from trauma before and during the surgical procedure. Long surgeries and procedures where much manipulation is performed will favor inflammation and will affect corneal transparency. They are less frequent in noncontact lens viewing systems. Epithelial defects heal with ocular occlusion and emollients. Some will require the use of therapeutic contact lenses. If epithelialization of the defect is delayed, the superficial layers of the stroma can infiltrate producing opacity. Diffuse opacities such as bullous keratopathy or band keratopathy result from damage to the corneal endothelium.

Ocular Hypertension and Glaucoma An increase in eye pressure is relatively common after vitrectomy23 and numbers greater than 30 mm Hg happen in 35% of cases in the 48 hours following a vitrectomy via pars plana.24 Previous or intraoperative scleral buckle surgery, panendophotocoagulation, the association of lensectomy and postoperative development of fibrin membranes have been described as risk factors of postoperative ocular hypertension. Eyes with previous glaucoma have a greater tendency to elevate pressure, since their drainage systems are compromised and their resistance to pressure increase is lessened. For this reason, they must be treated more aggressively. At evaluation time it is important to determine the state of the camerular angle. If open-angle glaucoma is present, the causes can be: inflammation, the presence of blood, silicone oil or gas in the anterior chamber, viscoelastics, incorrect mixtures of gas and its expansion, or the presence of neovessels in the angle. Treatment involves aqueous humor and carbonic anhydrase production inhibitors (by mouth or intramuscular) and anti-inflammatories. If the intraocular pressure (IOP) is very high, an anterior chamber paracentesis may be necessary or even a punctuation via pars plana with a 30-gauge needle to extract some gas when there is bulging in the anterior iris or crystalline lens.

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356 If the angle or the pupil is blocked by fibrin, an injection of 10–12 micrograms of recombinant tissue plasminogen activator (r-TPA) in the anterior chamber will dissolve the fibrin and improve ocular tension. A late increment in IOP can be secondary to the administration of topic or systemic corticosteroids, chronic inflammation or by ghost cells. If the iridocorneal angle is closed, we will consider the gas or silicone oil of the vitreous cavity as possible causes, or the mechanical effect of a very indented scleral band. If tension is very elevated, we will resort to hyperosmotic agents, topic corticosteroids and cycloplegics. We will insist on the correct prone position, evaluate iridectomy permeability and if it is necessary, evacuate some gas or oil to resolve the complication. If the above-mentioned problems are not present, aggressive treatment with topic or oral hypotensors and anti-inflammatories will decrease tension quickly. Iris neovascularization and camerular angle in diabetics or patients with retinal vascular occlusions can exist before vitreous surgery. Previous intraoperative photocoagulation and intraoperative endophotocoagulation reduce the incidence of neovessels in the iris. Nevertheless, sudden neovascular glaucoma can be present, and the degree of retinal ablation must be revised along with the assessment of the peripheral cryotherapy treatment. The presence of a rhegmatogenous RD in the vitrectomy postsurgical period in a patient with PDR usually evolves in neovascularization of the iris and the phthisis bulbi, if reattachment of the retina is not accomplished. When the neovascular process is stabilized and there is a secondary glaucoma, the options for treatment must be evaluated. It is important to warn patients who carry intraocular gas that atmospheric pressure variations will have an influence on the size of the gas bubble. If they fly or rapidly rise by more than 1,000 or 1,500 meters of altitude from the place where the gas was injected, the increment in volume can cause a pressure increase and severe eye pain. It is recommended to avoid flying until the gas bubble reduces to 10% its size and in case of necessary traveling to high altitude places, the ascent must be gradual to allow the eye to adapt to the increment in size of the gas bubble.25,26 The hyperbaric pressure condition produced during scuba diving practice or during hyperbaric oxygen treatments brings about a diminution of gas volume and ocular hypotony.27 The eye tries to compensate by producing aqueous humor, and the return to normal atmospheric pressure will generate an expansion of the gas bubble, causing important increments in eye pressure. Postvitrectomy glaucoma mechanisms are: ƒƒ Hemorrhage ƒƒ Inflammation (fibrinoid reaction) ƒƒ Choroidal edema ƒƒ Pupillary block

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357 ƒƒ ƒƒ ƒƒ ƒƒ

Intraocular gases Viscoelastics in the anterior chamber Silicone oil Neovascular glaucoma

Vitreous Hemorrhage This is the most common postoperative complication in PDR patients. Many patients present blood in the vitreous cavity in some degree after surgery, and in most cases, it clears up spontaneously.

Early (First Month) These are usually mild and bleeding is caused by remains of red blood cells left over in the peripheral vitreous. When they originate in bleeding points treated during vitrectomy (neovessel proliferations in the retina or optic disk) blood is usually denser. If the hemorrhage does not clear up, we must check eye pressure to rule out ghost cell glaucoma, and perform echographies to rule out RD.

Late (After the First Month) These are more serious and can cause repetitive hemovitreous hemorrhages. They are usually produced by anterior neovessel proliferation at sclerotomy level. If they do not improve, pars plana vitrectomy (PPV) must be performed within a month. We must suspect RD or anterior hyaloidal fibrovascular proliferation (AHFVP) if a dense vitreous hemorrhage with neovessels in the iris and hypotonia are present. Anterior hyaloidal fibrovascular proliferation28,29 is a serious complication which may appear from the 3rd week to the 3rd month after surgery. It is caused by a proliferation of highly vascularized fibrous tissue, clinically manifested by retrolental vitreous hemorrhage associated with retinal and ciliary body detachment, which cause the hypotonia also associated with the profile (Fig. 10). Young diabetic patients badly controlled or photocoagulated later than they should have been, as well as adults with aggressive diabetes, are more likely to suffer with this complication. Retinal detachment presence, multiple surgeries and the need for cerclage can also favor it. In general terms, treatment would consist of vitrectomy, lensectomy, RD treatment (PFCL), retinotomy if needed, treatment of anterior hyaloid proliferation with diathermia or cryotherapy, scleral procedure and silicone oil according to the case (Fig. 11).

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Figure 10

Anterior hyaliod fibrovascular proliferation: note the retrolental vitreous hemorrhage and the ectropion uveae

Figure 11

Anterior hyaloids fibrovascular proliferation after surgery

Retinal Detachment Retinal Detachment Exudative It is not uncommon in extensive and confluent panphotocoagulation in patients with neither previous nor surgical tears. It typically appears in the inferior area.

Retinal Detachment Due to Posterior Break It is produced when a previously treated posterior break reopens due epiretinal membrane traction. Surgery must not be delayed in order not to develop PVR. A new three-port PPV is necessary to extract epiretinal membranes and reapply the retina. The break is treated again and long-acting gas is left.

Retinal Detachment Due to Anterior Break The presence of RD in vitreoretinal surgery postoperatively can happen in easy surgeries as well as in difficult ones. It is caused by undiagnosed peripheral tears or by the contraction of the vitreous base.

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359 Treatment must be assessed in each case based on tear size and position. Small and superior ones can be treated injecting gas or air followed by a pexia system, if the retina is reattached. In larger or inferior breaks, a scleral procedure with or without gas injection would be indicated according to the requirements of the case.

Proliferative Vitreoretinopathy The postoperative development of a RD with associated PVR is a serious complication which, in its most severe extremes, can cause serious vision loss. It can occur after any vitrectomy but it is more frequent when large and multiple tears are present, as well as in cases of long evolution of the detachment, association of choroidal detachment and especially, after excessive cryotherapy treatment or with retinal incarceration.30 Proliferative vitreoretinopathy can appear as a complication in the evolution of rhegmatogenous RD, but more frequently, it arises as a surgical complication, and in large part, it is an iatrogenic disease. There are some risk factors, some of which are surgical PPV complications, which favor it:

Clinical Factors ƒƒ Characteristics of RD:

– Evolution time – Size and number of tears – Multiple and large horseshoe tears – Giant tear – Preoperative PVR – Old patient – Biologic typology ƒƒ Hemovitreous ƒƒ Choroidal detachments: intraocular inflammation ƒƒ Ocular trauma

Surgical Factors ƒƒ Failed previous surgeries ƒƒ Surgical complications

– Retinal incarceration ƒƒ Surgical manipulations – Retinopexy (especially excessive cryotherapy) – Tamponades

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360

Intraocular Inflammation and Fibrinoid Reaction After vitrectomy a certain degree of intraocular inflammation is common, especially when it is associated with a lensectomy, intraocular gas, laser therapy, and in particular, cryotherapy. In most situations, treatment with topic corticosteroids is sufficient to improve the process. A fibrinoid reaction in the anterior chamber can occur in vitrectomies performed to repair a RD with PVR in diabetic patients with severe PDR, particularly poorly controlled young patients or young patients with kidney failure. Therefore mentioned complication is more habitual if it is associated with anterior segment surgery. As prevention, a treatment with frequent use of topical corticosteroids is indicated. In case of moderate or severe fibrinoid reaction, inject 10–12 μg of r-TPA with a 30-gauge needle into the anterior chamber31 (Figs 12A and B). Never use this substance in the immediate postoperative, to avoid bleeding, or 72 hours after the fibrin has been established, because it has very little effect. Mild fibrinoid reactions are often treated with hourly topical corticosteroids. Massive fibrin formation in the vitreous cavity is another severe complication that may occur after a vitrectomy for PDR. The use via pars plana not more than 25 μg of r-TPA can help to control massive fibrin response but generally is best managed with a repeated vitrectomy with fibrin removal.32,33

Tamponade and Manipulator Agents Complications Intraocular Gas Some of the complications associated with the use of gas as a tamponade agent include an elevation of IOP, the occlusion of the central artery of the retina, injury to the optic nerve (Fig. 13) and the flattening of the anterior chamber (Table 2).

A

B

Figures 12A and B (A) Severe fibrinoid reaction; (B) The same case few minutes after recombinant tissue plasminogen activator treatment

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Figure 13 Nerve atrophy, secondary to ischemic optic neuropathy in a retinal detachment surgery with vitrectomy. In a vitrectomy, it is very important to maintain a right intraocular pressure control. In cases of high intraocular pressure maintained you could have a vascular occlusion

TABLE 2 Most common gases Expansion

Nonexpansive concentration

Length

Air

x 1

-

1–2 days

SF6

x 2

20%

2–3 weeks

C3F8

x 4

15%

6–8 weeks

During vitrectomy, the selected gas is mixed with a certain amount of filtered air to achieve a nonexpansible mixture which remains in the eye for as long as it is required. It is essential to avoid gas mixing errors to prevent complications. If there is too much gas in the mixture, the gas will expand and cause ocular hypertension problems and even, shallowing of the chamber.34 If the proportion of air is greater, the air-gas bubble will reabsorb too quickly. If the vitrectomy has been incomplete or much subretinal fluid has been left, the bubble will be very small at the end of the surgery. Gas can leak spontaneously through the sclerotomy (a poorly sutured sclerectomy) or forcibly, if something (i.e. choroidal detachment) increments eye pressure. Nitrous oxide anesthesia must be avoided during retinal surgery when an intraocular gas bubble is placed in the eye. If nitrous oxide anesthesia is used it should be discontinued about half an hour before the gas is instilled into the eye (see chapter 4). A subretinal migration of the gas is rare but can arise when there are large tears or the retina is too tight or when gas is injected in the subretinal area. Gas can move into the anterior chamber through wide capsulotomies

Step by Step Vitrectomy

362 or through zonular dehiscence, but will not cause major problems as long as a prone position is maintained which prevents gas from touching the endothelium.

Silicone Oil Silicone oil is a long-term tamponade which must be used in complex cases or when the patient cannot follow the postural treatment properly. The main intraoperative complication during silicone oil instillation is that of overfill. If the IOP is not controlled and we try to overfill the eye with silicone oil, then zonular rupture generally ensues and a silicone oil bubble gains access to the anterior chamber. We must prevent this complication lowering air infusion pressure and stop injecting once silicone can be seen refluxing back up the air infusion line. Another problem arises when silicone gains access to subretinal space through a pre-existing retinal tear. This complication may be avoided removing all tractions around retinal breaks and performing a fluid-air exchange. If silicone oil is left inside the eye, it will generally produce secondary complications after a few months.35,36 Thus, we must attempt its removal in 3–6 months, unless the risk of RD recurrence is very high. Whenever silicone oil is injected in aphakic patients, an inferior iridotomy with vitreotome must be performed.37 Pupillary and iridotomy blocking can arise in the immediate and also late postoperative period due to a fibrin deposit. The silicone oil then moves into the anterior chamber causing ocular hypertension. An iridotomy with laser YAG will be necessary to revert the blockage. The tamponade effect of silicone oil of 1,000 centistokes and 5,000 centistokes (cSt) is similar. The tendency to emulsificate is lesser in the second, and for this reason, it should be the choice in cases where oil removal is not anticipated. When silicone oil moves into the anterior chamber, it is toxic for the corneal endothelium and for the trabecular meshwork, often causing glaucoma. If the patient is phakic, a cataract will very likely develop within a few months, in which case a combined procedure of gas removal and cataract surgery is indicated (Fig. 14). Silicone oil postoperative complications are: ƒƒ Emulsification (Fig. 15) ƒƒ Cataract ƒƒ Pain: Subconjunctival oil (Fig. 15) ƒƒ Corneal edema and band keratopathy ƒƒ Closure of inferior iridectomy ƒƒ Glaucoma ƒƒ Iritis ƒƒ Rubeosis iris ƒƒ Postoperative RD – After oil removal – With oil present ƒƒ Persilicone oil fibrous proliferation

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363

Figure 14

Secondary cataract produced by silicone oil tamponade

Figure 15

Emulsified silicone oil in the anterior chamber and subconjunctival oil infiltration

Perfluorocarbon Liquids The use of PFCL has few complications. The main complication is postoperative intraocular retention, which may cause toxicity in the tissues by persistent contact. Perfluorocarbon remnants may enter the anterior chamber through zonulocapsular barrier defects and cause visual acuity fluctuations and endothelial toxicity. If these symptoms are serious, perfluorocarbon (PFC) remnants must be all removed (Fig. 16). Subretinal retention of PFC bubbles can be originated in surgeries where large peripheral retinotomies are required, and if they are located outside the macular area, they do not seem to cause any anatomic or visual acuity alterations.38

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364

Figure 16

Perfluorocarbon liquid remnants in the anterior chamber

Endophthalmitis This is a rare postvitreous surgery complication which manifests itself in intense pain, hypopyon and visual acuity diminution 36–48 hours after surgery. Its proper diagnose may be delayed because its symptoms are common in a vitreous surgery. In cases where the ocular fundus can be evaluated, the existence of intraretinal hemorrhages and periphlebitis may be an early sign of endophthalmitis.39 When this condition is suspected, a sample of aqueous and vitreous humor must be taken for culture, followed by intravitreous administration of antibiotics. Topic and systemic antibiotics should be also prescribed, which can be modified according to culture and antibiogram results. Topic and systemic corticosteroids are prescribed to control intraocular inflammation.

Cataract The progressive opacification of the crystalline lenses or the progression of a previous cataract is common after vitrectomy. Up to 80% of patients show nuclear sclerosis progression 2 years after vitreous surgery, especially if it is associated with gas or silicone oil use.40,41 A posterior subcapsular opacity, in the form of vacuoles, related to the use of gas as an intraocular tamponade,42 can arise during the immediate postoperative period. It is critical to position the patient correctly while the intraocular bubble is large. These subcapsular vacuoles tend to disappear within a few days, but if they are numerous in 40–50-year-old patients, they can evolve into permanent posterior subcapsular opacities (Fig. 17). Young patients (younger than 50 years old) show a lesser tendency to develop cataract after vitrectomy, with an incidence of 7% after 2 years,43 although their evolution may be strongly influenced by the requirement of a complex surgical procedure.44

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365

Figure 17

Permanent subcapsular opacities related with long-acting gas use

TO PREVENT VITRORETINAL SURGERY COMPLICATIONS ƒƒ All surgical team members (assistants and nurses included) must be ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ ƒƒ

acquainted with posterior vitrectomy surgical techniques The surgeon must be comfortably positioned and instruments must be inspected and tested prior to their introduction into the eye Always work with a systematic plan and well-established surgical objectives Do not open the passage of fluid of the infusion cannula until making sure it is in the interior of the vitreous cavity Use a careful surgical technique to avoid iatrogeny (hemorrhages, tears, scleral perforations during buckling surgery, phototoxicity, etc.) Try to anticipate risk situations and factors. Prevent and treat them prophylactically if it is possible Avoid hypo-and hypertonic situations which promote bleeding and visualization problems. Try to work with infusion pressures of 20–30 mm Hg Minimize the number of entries and exits into and out from the eye Clean the incarcerated vitreous with the vitreotome in sclerotomies. Avoid tractions of the vitreous Revise the peripheral retina with indentation before proceeding to air exchange and at the end of the surgery. Treat tears adequately Correct use of retinopexy systems. Avoid excessive or deficient treatments Suture sclerectomies and conjunctiva very carefully Give the patient and their family adequate instructions of postoperative treatment and reasons for urgent consultation.

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366

REFERENCES 1. Corcóstegui B, Adán A, García-Arumí J, et al. Cirugía vitreorretiniana, indicaciones y técnicas. Madrid. Tecnimedia (Ed); 1999. pp. 47-8. 2. Smiddy WE, Michels RG, Green WR. Lens and peripheral retinal relationships during vitrectomy. Retina. 1991;11(2):199-203. 3. Guyer D, Yannuzzi L, Chang S, et al. Retina-Vitreous-Macula: Saunders Company; 1999. pp. 1312-3. 4. de Juan E, Landers MB. New technique for visualization of infusion cannula during vitreous surgery. Am J Ophthalmol. 1984;97(5):657-8. 5. Krupin T, Kolker A, Rosenberg L. Complications in ophthalmic surgery. Harcourt. 2000;324. 6. Schulze S, Sekundo W, Kroll P. Autologous serum versus hyaluronic acid eye drops for the treatment of corneal erosions after vitrectomy in diabetic patients. A prospective randomized study. Ophthalmologe. 2005;102(9):863-8. 7. Eckardt C. Pupillary stretching. A new procedure in vitreous surgery. Retina. 1985;5(4):235-8. 8. Blankenship GW, Flynn HW, Kokame GT. Posterior chamber intraocular lens insertion during pars plana lensectomy and vitrectomy for complications of proliferative diabetic retinopathy. Am J Ophthalmol. 1989;108(1):1-5. 9. MacCumber MW, Packo KH, Civantos JM, et al. Preservation of anterior capsule during vitrectomy and lensectomy for retinal detachment with proliferative vitreoretinopathy. Ophthalmology. 2002;109 (2):329-33. 10. Chalam KV, Shah VA, Gupta SK, et al. Evaluation and comparison of lens and peripheral retinal relationships with the use of endolaser probe and newly designed curved vitrectomy probe. Retina. 2003;23(6):815-9. 11. Smith JM, Steel DH. Anti-vascular endothelial growth factor for prevention of postoperative vitreous cavity haemorrhage after vitrectomy for proliferative diabetic retinopathy. Cochrane Database Syst Rev. 2011 May 11;(5):CD008214. 12. Piper JG, Han DP, Abrams GW, et al. Perioperative choroidal hemorrhage at pars plana vitrectomy. A case-control study. Ophthalmology. 1993;100(5):699-704. 13. Awh CC, Schallen EH, De Juan E. An illuminating laser probe for vitreoretinal surgery. Arch Ophthalmol. 1994;112(4):553-4. 14. Peyman GA, D’Amico DJ, Alturki WA. An endolaser probe with aspiration capability. Arch Ophthalmol. 1992;110(5):718. 15. Corcóstegui B, Adán A, García-Arumí J, et al. Cirugía vitreorretiniana, indicaciones y técnicas. Madrid. Tecnimedia; 1999. p. 155. 16. de Bustros S, Glaser BM, Johnson MA. Thrombin infusion for the control of intraocular bleeding during vitreous surgery. Arch Ophthalmol. 1985;103(6):837-9. 17. Verdoorn C, Hendrikse F. Intraocular human thrombin infusion in diabetic vitrectomies. Ophthalmic Surg. 1989;20(4):278-9. 18. McLeod D, James CR. Viscodelamination at the vitreoretinal juncture in severe diabetic eye disease. Br J Ophthalmol. 1988;72(6):413-9. 19. Carter JB, Michels RG, Glaser BM, et al. Iatrogenic retinal breaks complicating pars plana vitrectomy. Ophthalmology. 1990;97(7):848-53. 20. Oyakawa RT, Schachat AP, Michels RG, et al. Complications of vitreous surgery for diabetic retinopathy.I. Intraoperative complications. Ophthalmology. 1983;90(5):517-21.

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367 21. Campochiaro PA, Kaden IH, Vidaurri-Leal J, et al. Cryotherapy enhances intravitreal dispersion of viable retinal pigment epithelial cells. Arch Ophthalmol. 1985;103(3):434-6. 22. Chung H, Tolentino FI, Cajita VN, et al. Reevaluation of corneal complications after closed vitrectomy. Arch Ophthalmol. 1988;106(7):916-9. 23. Campbell DG, Simmons RJ, Tolentino FI, et al. Glaucoma occurring after closed vitrectomy. Am J Ophthalmol. 1977;83(1):63-9. 24. Han DP, Lewis H, Lambrou FH, et al. Mechanisms of intraocular pressure elevation after pars plana vitrectomy. Ophthalmology. 1989;96(9):1357-62. 25. Lincoff H, Weinberger D, Reppucci V, et al. Air travel with intraocular gas. I. The mechanisms for compensation. Arch Ophthalmol. 1989;107(6):902-6. 26. Lincoff H, Weinberger D, Stergiu P, et al. Air travel with intraocular gas. II. Clinical considerations. Arch Ophthalmol. 1989;107(6):902-10. 27. Jackman SV, Thompson JT. Effects of hyperbaric exposure on eyes with intraocular gas bubbles. Retina. 1995;15(2):160-6. 28. Lewis H, Abrams GW, Foos RY. Clinicopathologic findings in anterior hyaloidal fibrovascular proliferation after diabetic vitrectomy. Am J Ophthalmol. 1987;l04(6):614-8. 29. Lewis H, Abrams GW, Wiliams GA. Anterior hyaloidal fibrovascular proliferation after diabetic vitrectomy. Am J Ophthalmol. 1987;104(6):607-13. 30. Cowley M, Conway BP, Campochiaro PA, et al. Clinical risk factors for proliferative vitreoretinopathy. Arch Ophthalmol. 1989;107(8):1147-51. 31. Jaffe GJ, Abrams GW, Wiliams GA, et al. Tissue plasminogen activator for postvitrectomy fibrin formation. Ophthalmology. 1990;97(2):184-9. 32. Sebestyen JG. Fibrinoid syndrome: a severe complication of vitrectomy surgery in diabetics. Ann Ophthalmol. 1982;14(9):853-6. 33. Dabbs CK, Aaberg TM, Aguilar HE, et al. Complications of tissue plasminogen activator therapy after vitrectomy for diabetics. Am J Ophthalmol. 1990;110(4):354-60. 34. Han DP, Lewis H, Lambrou FH, et al. Mechanisms of intraocular pressure elevation after pars plana vitrectomy. Ophthalmology. 1989;96(9):1357-62. 35. Federman JL, Schubert HD. Complications associated with the use of silicone oil in 150 eyes after retina-vitreous surgery. Ophthalmology. 1988;95(7):870-6. 36. Riedel KG, Gabel VP, Neubauer L, et al. Intravitreal silicone oil injection: complications and treatment of 415 consecutive patients. Graefes Arch Clin Exp Ophthalmol. 1990;228(1):19-23. 37. Ando F. Intraocular hypertension resulting from pupillary block by silicone oil. Am J Ophthalmol. 1985;99(1):87-8. 38. García-Valenzuela E, Ito Y, Abrams GW , et al. Risk factors for retention of subretinal perfluorocarbon liquid in vitreoretinal surgery. Retina. 2004;24(5):746-52. 39. Packer AJ, Weingeist TA, Abrams GW. Retinal periphlebitis as an early sign of bacterial endophthalmitis. Am J Ophthalmol. 1983;96(1):66-71. 40. de Bustros S, Thomson JT, Michels RG, et al. Nuclear sclerosis after vitrectomy for idiopathic epiretinal membranes. Am J Ophthalmol. 1988;105(2):160-4. 41. Cherfan GM, Michels RG, de Bustros S, et al. Nuclear sclerotic cataract after vitrectomy for idiopathic epiretinal membranes causing macular pucker. Am J Ophthalmol. 1991;111(4):434-8.

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368 42. Hsuan JD, Brown NA, Bron AJ, et al. Posterior subcapsular and nuclear cataract after vitrectomy. J Cataract Refract Surg. 2001;27(3):437-44. 43. Melberg NS, Thomas MA. Nuclear sclerotic cataract after vitrectomy in patients younger than 50 years of age. Ophthalmology. 1995;102(10):1466-71. 44. Blodi BA, Paluska SA. Cataract after vitrectomy in young patients. Ophthalmology. 1997;104(7):1092-5.

Index

A Absorption different wavelengths 98 optimal hemoglobin and oxyhemoglobin 97 Accurus pressure pump 73 Accurus vitreotome, using the dual vitrectomy mode 368 Age-related macular degeneration 267 better visual result with surgery in cases associated with 267 intravitreal ranibizumab injection in eyes with 314 treatments trials study 368 Air-filled phakic eye 51 Air-gas exchange 148 close the last sclerotomy 148 end of surgery 148 Ampoule of the hypnotic agent, use of local anesthesia 37 Anesthesia anatomy applied to 31 types of 29 general 29 local 30 peribulbar 35

sub-Tenon’s 36 transconjunctival retrobulbar 37 Anterior epiretinal proliferation removal of 298 Antiplatelet and anticoagulants 316 Aphakic or pseudophakic eyes 170, 275, 278, 283 Applanation tonometry 10 Argon laser 96 drawbacks, absorbed hemoglobin 96 melanin 96

B Backflush and extrusion functions 91 Berger’s space 2 Biconcave lens 51 Landers 50 use for fluid/air exchange 57 Bimanual dissection 255, 256, 326 surgery 60, 63, 68 Biomicroscopy of the retina 11 Bipolar diathermy 91

Step by Step Vitrectomy

370 Blunt-tipped 106 Buckle on the sclera accurate placement of 274

C Capsular rupture 206 Capsule to the sulcus 224 Capsulectomy 175 Cataract surgery 99, 128, 138, 202, 217 Central displacement of the retina (R) 294 Central posterior fundus 51 Central vitreous 51 Chandelier in a pars plana position 68 Chang cannula 143, 219, 368 Chorioretinal adhesion 301, 302 Choroid hemorrhagic detachment, ultrasound image of 15 Choroid highly echogenic convex lines in a B-scan 16 Chronic intraocular inflammation 181 Ciliary body 5, 6, 28, 181 processes 168 sulcus 168 Cloquet’s canal 2 Coagulate in choroid hemorrhage 16 Conjunctiva, opening of 76 Conjunctival displacement 285 incisions 123 opening 124 Constellation vision system 85, 87 Corcóstegui’s direct action forceps 107 Cornea and crystalline lens 10 Corneal dehydration maneuver 347 Corneal edema 181, 226 incision 152 limbus 4, 5 lens material 158 Cryotherapy 354

Crystalline lens abundance of 181 fragments 180 surgery 10 Cystoid macular edema 24

D De Juan hook 127 Delaminating membranes 135 Densiron 119 Detachment of the posterior vitreous, differential diagnosis 13 Diabetic macular edema 24, 25 Diabetic retinopathy 14, 162, 320, 324, 326 Diabetic retinopathy and endoscopic vitrectomy 176 Diamond-coated foreign body forceps 107 Diathermy device 324, 324 forceps and erasers 91 Diffuse posterior contraction 293 Diode laser 96 Direct exchange for silicone oil 146 Diseases corneal 354 diabetic eye 112, 328, 367 hyperacute 244 iatrogenic 359 macular 11, 17, 26 neurological 30 occlusive venous 94 primary disease 262 retinal vascular disease 272, 307, 314 segment 194 thromboembolic 316 valve disease 28 vascular ischemia in diseases 17 vitreoretinal 1, 314 vitreous interface 261 Disk and macula edema 247 Dislocated lens 217 Dislocated posterior chamber phakic refractive lens 217

Index

371 DoRC silicone retaining ring 49 DoRC’s backflush probe 84 illuminating infusion cannula 77 sutureless infusion cannula 77 23-gauge diathermy instrument 91 27-gauge light fiber 198 27-gauge vitrector 197 Double lumen 143

E Ectropion uveae 358 Edematous epithelium 347 Emulsification of the silicone oil 150 Encircling exoplants 275 Encircling procedure 276 Endodiathermy final stage of 324 initial stage of 324 Endoillumination probe 130 Endoillumination systems 65 Endoilluminator 301 Endolaser 354 Endophotocoagulation 93, 94, 174 Endophthalmitis, early 245 Epiretinal membranes attached to the retinal surface 23 complete macular hole associated 20 subfoveal cotton ball sign 22 tridimensional reconstruction of 23 Epithelial erosions 10 Erect indirect binocular ophthalmic system, use of 56 External segment of the cones 22 Extraction of the tip of the phacofragmenter fragments 158 Extraocular muscles 4 Extrusion system 83

F Fibrovascular tissue connections 251 Fluorescein angiogram 318, 327 Fluorescein angiography 16

Focal posterior contraction 292 Fragments of crystalline lens 181

G Giant retinal tear 141, 305 Goldmann lens 11 Goldmann three mirror lens 60 Green diode laser 96 Greenbaum cannula 37 Grieshaber pressure pump 74

H Healed posterior laceration 240 Heavy silicone oil 117 Hemorrhagic choroid detachment ultrasound image of 15 High intraocular pressure 75, 326 Hyaliod fibrovascular proliferation 358 Hyaluronic acid 109 Hydrostatic pressure 71 Hypotony 288

I Iatrogenic retinal tear 353 Illuminated 20-gauge vitrectomy probe from DoRC 69 Illuminated laser probe 94 Implanting an aphakic artisan lens 221 Indirect ophthalmoscopic visualization 275 Indocyanine green 136 Inferior and posterior tamponade 118 Inferior peripheral iridectomy 151 Inferior temporal scleral incisions 124 Inferotemporal quadrants 14 Infusion devices systems 71, 76 Infusion pump or gas forced infusion 72 Infusion terminal 301 Inner and outer segments 21 Instrumentation 196

Step by Step Vitrectomy

372 Integrated vitrectomy systems 45 Internal and external segments of the photoreceptors 22 Internal limiting membrane 106, 251 Internal nuclear layer 21 Internal systems 65 Intraocular foreign body 14 extraction with magnet and forceps 243 Intraocular gas 113, 360 inflammation and fibrinoid reaction 360 lens complications 350 lens dislocation 216 lens implantation 161, 326 pressure 72, 77, 78, 322, 325 silicone oil in ocular severe trauma 239 tamponade 283, 302 Intraoperative bleeding controlling of 172 during vitreoretinal surgeries from many etiologies 315-319 choroidal detachment 188, 303 complications 237, 343 fundus photograph 252 hemorrhage 30 hemosis 192 hypotony 268 lesion 238 macular hole 268 management of perfluorocarbon liquids 142 myosis 159 oCT 368 posterior segment bleeding control, techniques of 320 pupil block 128 retinal breaks 288 suture placement 255 visualization 10 Intravitreal air injection 325

autologous plasmin 341 bevacizumab injection of anti-VEGF 317, 320 autologous plasmin 340 ranibizumab 319 Iris neovessels, bleeding of 351 Irregular full-thickness retinal folding 293 Isolate fibrovascular proliferations 353

L Lamellar macular hole, associated an epiretinal membrane 20 Landers biconcave lens 50 Landers lens retaining 49 Laser endophotocoagulation 93 photocoagulation 301, 325 Leica microscope 47 Lens convexity of 160 dislocation 211 Lensectomy and intraocular lens 296 Limbal incision 152 Limbal peritomy and relaxing incisions 273 Linear suction power 83 Luxated natural or intraocular lenses 142 subluxated intraocular lenses 14

M Machemer contact lens 61 magnifying lens 51 plano-concave lens 52 Macular hole complete 20 index 21 Magnet and intraocular forceps 243 Manual backflush, aspiration cannula capable of 133

Index

373 Medtronic’s cannulas 91 Membranectomy 174 Meshwork of collagen fibers 2 Metallic valved trocar for 27-gauge vitrectomy 197 Microincision vitrectomy drawbacks of 192 Microvitreoretinal blade 6 Minimal residual leakage nasal 327 Müller cell layer 4 Multifunctional microscope 46 Multiple isolated single star folds 292 Myosis 347 Myringotomy blade 301

N Neovascularization of the iris with opacity of the media 177 Nerve atrophy 361 Noncontact systems 122 Nonexpanding gas 147 Nucleus of the lens 158

O ocular endoscopy with image and illumination 165 hypertension and glaucoma 355 hypotony and bulb phthisis 247 media 10 perforation in retrobulbar anesthesia 202 trauma with or without intraocular foreign body 160 oil extraction and insertion of intraocular lens 239 opacification of the lens 159 opaque vitreous proceeds posteriorly, removal of 279 ophthalmologic endoscope 165 surgery table 43 optic nerve disk 14

optic nerve using intraocular forceps 253 optical coherence tomography 19-22, 256, 338, 340, 341 ora serrata, real view of 168 orbit anatomy 32 oxane HD 117, 118

P Panoramic illumination probe 66 Panphotocoagulation 254 Panretinal endophotocoagulation 324, 326 Panretinal photocoagulation 10 Pars plana lensectomy 161, 159, 175 Pars plana lensectomy advantages of 158 indications of 368 surgical technique 156 with silicone oil injection 307 Pars plicata of the ciliary body 295 Peeling membranes in vitrectomy 132 Perfluorocarbon liquids properties of 111 using a Chang cannula 111 Peribulbar anesthesia 35, 37 Periphery beyond the equator 51 Periphery using the vitreotome 131 Periretinal membranes 292 Peristaltic pumps 80 Peyman wide-angle lens 52 Phacoemulsification 99, 128, 326 Phacofragmentation of the nucleus with the aid of the endoillumination probe 214 Phthisis bulbi 10 Polishing of the anterior capsule 161 Posterior hyaloid detachment advanced phase of 325 Posterior hyaloid over an epiretinal membrane 23 Posterior retinal iatrogenic tears 353 Posterior surface of the iris 295

Step by Step Vitrectomy

374 Post-traumatic detachment and reparation with intraocular silicone oil 241 Post-traumatic macular hole 247 Postvitrectomy epithelial defect in a diabetic patient 355 Potential problems during the use of perfluorocarbon 146 Preoperative intravitreal anti-VEGF injection, technique of 319 Proliferative diabetic retinopathy anterior proliferation of 325 Proliferative diabetic retinopathy vitrectomy 353 Proliferative vitreoretinopathy adjunctive treatment 304 classification of 290 diagnosis of 290 surgery of 295 Pupil management 127 Pupil reflexes 9 Pupillary margin 295

Q Quartz lens 64

R Radial retinal folds 294 Rectus inferior 4 lateral 4 superior 4 Retina or choroid 13 Retinal detachment due to anterior break 358 exudative 358 surgery 177 with proliferative vitreoretinopathy 307 Retinal iatrogenic tears 352 Retinal tears 287, 291, 346, 352 Retinopexy, complications 354 Retinoschisis 14 Retrobulbar block 33

Retrobulbar hemorrhage 205 Retrobulbar needle 38 Retrolental vitreous hemorrhage 358 Rhegmatogenous retinal detachment 291 Rubeosis iridis 10 Rupture of the posterior capsule 161

S Scleral buckle 10, 14 Scleral buckling in proliferative vitreoretinopathy 296 Scleral buckling technique 273 Scleral indentation 178 Scleral peak 13 Scleral suture technique 277 Sclerocorneal limbus 6 Sclerotomies with 23-gauge vitrectomy 284 25-gauge vitrectomy 284 Sclerotomy complications 343 enlargement 346 pediatric vitrectomy 6 tunnel 287 Segmentation of proliferative membranes 326 Segmenting membranes 134, 135 Sign of an attached posterior hyaloid 130 endophthalmitis, early 364 heating of the phacofragmenter 157 protein coagulation 159 vitreomacular traction 24 Silicone oil removal of 151, 303 solvent 116 tamponade, indications of 150 tip arches 131 tipped cannula 83, 131 Slit lamp microscopy 10 Spiral of Tillaux marks 5 Staining membranes 136 Staphylococcus epidermidis 226 Stellaris PC 46

Index

375 Stellaris PC vision enhancement system 88 Stryker Stretcher for ophthalmology surgery 44 Subconjunctival oil infiltration 363 Subfoveal cotton ball sign 22 Subfoveal fluid 256 Subfoveal perfluorocarbon bubbles 270 Submacular hemorrhage located into the macular area 267 Subretinal macular space, surgery of 267 Subretinal proliferation, removal of 298 Sulcus fixation of an intraocular lens 224 Syndromes capsular contraction 223 Ehlers-Danlos 223 fibrinoid 367 Floppy iris 127 managing sunset 232 Marchesani 223 Marfan syndrome 223 pseudoexfoliation 206, 217, 223 vitreocorneal touch 206 vitreomacular traction 3, 22, 24, 27, 139, 189, 261, 342, 340 Synergetic laser probe allowing a straight or curved approach 95

T Tamponade and manipulator agents complications 360 Temporal vitreomacular traction syndrome 24 Tenon’s capsule 274 Tolentino thirty degree prism lens 52 twenty degree prism lens 52 Tortuous retinal vessels 292 Traction forces 251 Transconjunctival injection process 39 retrobulbar anesthesia 37 sub-tenon’s anesthesia 203 Transilluminator light 10 Transscleral cryopexy 179

Trauma and dense vitreous hemorrhage 240 Trauma and endophthalmitis 244 Trauma and intraocular foreign body 241 Trauma and retinal detachment 241 Triamcinolone acetonide 139 Tridimensional reconstruction of an epiretinal membrane 23 Tripod-shaped forceps 107 Trypan blue 137 Tumors intraocular 15 masses 15 size of 12 structure of 12

U Ultrasonic fragmentation 102 Ultrasonography 11 Unilateral submacular hemorrhage 269

V Valved trocars preventing the leakage of saline 78 use of 76, 322 Vascular arcades 14 endothelium growth factor 313 entoptic test 10 ischemia 17 Vented gas forced infusion system 73 Venturi pump 80 Vertical scissors of the ACCURUS system 104 Vision with rotation 90° 168 Visual acuity 9, 255, 256, 327 Vitrectomy anatomical distances 4 basic operative steps in primary 277 benefits of microincision 192 compliactions of the ocular trauma 246

Step by Step Vitrectomy

376 diabetic macular edema 257 endoscopic 180, 181 following vitreous loss 206 open traumatisms 235 probe 83, 140 proliferative vitreoretinopathy 297 retinal detachment with proliferative vitreoretinopathy 288 surgery after combined cataract 109, 128 combined phacoemulsification 99 twenty five gauge 193 twenty gauge caliber surgery 189 twenty three gauge 184, 187 use of gas in 147 use of ultrasound 102 Vitreomacular traction syndrome 21, 24, 324 Vitreoretinal bleeding 315 proliferation 141, 159 anterior 160 surgery 172 characteristics of some of the antiaggregants used for 29 complications of 171 traction syndrome 22 traction syndrome in optical coherence tomography 338 Vitreotome cutter lens injury that develops cataract in the postoperative period 350 Vitreotome in position 130 Vitreous anatomy of 1, 3 anterior displacement of 295, 301 base and vitreoretinal interface 2 cavity 180, 327, 345 chamber 217 cutter 158, 161, 324 disorder 12 gel and the lens material 161 anterior 158 hemorrhage 10, 13, 129, 130, 177, 357 humor anatomy of 3

implant visible in the inferior zone of the vitreous cavity 335 incarceration 171, 172 infiltration 226 material inside the lens 161 space collagenous tissue 301 substitutes manipulators of tissues 109 tamponade 113 tractions 353 Vitroretinal surgery complications of 365 Volk self-stabilizing vitrectomy lens 50 Vortex veins and their anatomical relations 7

W Warfarin 368 Wide-angle-viewing systems 52, 53 Wide-field BIoM system 53 Wieger’s hyaloidocapsular ligament 2 Woldoff biconcave prism lens 52 Wound closure remove the cannulas 286 vitreous plugging 286

X Xanthophyll pigments of the macula 88

Y Yellow laser 97 absorption at different wavelengths 98 endo-ocular laser treatment 97 endophotocoagulation 97

Z Zeiss microscope with slit lamp 61 Zone of the iris 181