Cornea (Wills Eye Institute Atlas Series)

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Wills Eye Hospital

COLOR ATLAS & SYNOPSIS OF Clinical Ophthalmology

Christopher J. Rapuano SERIES EDITOR Cornea Cornea FOURTH EDITION

Christopher J. Rapuano

COLOR ATLAS & SYNOPSIS OF Clinical Ophthalmology Wills Eye Hospital

Cornea FOURTH EDITION

EDITOR Christopher J. Rapuano, MD Director and Attending Surgeon, Cornea Service Wills Eye Hospital Professor of Ophthalmology Sidney Kimmel Medical College at Thomas Jefferson University Philadelphia, Pennsylvania SERIES EDITOR Christopher J. Rapuano, MD Director and Attending Surgeon, Cornea Service Wills Eye Hospital Professor of Ophthalmology Sidney Kimmel Medical College at Thomas Jefferson University Philadelphia, Pennsylvania

Wills Eye Hospital COLOR ATLAS & SYNOPSIS OF Clinical Ophthalmology

Cornea FOURTH EDITION

Acquisitions Editor: Christopher Teja Editorial Coordinator: Lauren Pecarich Marketing Manager: Rachel Mante Leung Production Project Manager: Barton Dudlick Design Coordinator: Stephen Druding Manufacturing Coordinator: Beth Welsh Prepress Vendor: S4Carlisle Publishing Services Fourth Edition Copyright © 2024 Wolters Kluwer.

All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright. To request permission, please contact Wolters Kluwer at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email at permissions@lww.com, or via our website at shop.lww.com (products and services). 9 8 7 6 5 4 3 2 1 Printed in the United States of America

Library of Congress Cataloging-in-Publication Data ISBN-13: 978-1-975214-97-5 ISBN-10: 1-975214-97-8 Library of Congress Control Number: 2024902591

This work is provided “as is,” and the publisher disclaims any and all warranties, express or implied, including any warranties as to accuracy, comprehensiveness, or currency of the content of this work. This work is no substitute for individual patient assessment based upon healthcare professionals’ examination of each patient and consideration of, among other things, age, weight, gender, current or prior medical conditions, medication history, laboratory data, and other factors unique to the patient. The publisher does not provide med ical advice or guidance, and this work is merely a reference tool. Healthcare professionals, and not the publisher, are solely responsible for the use of this work, including all medical judgments, and for any resulting diagnosis and treatments. Given continuous, rapid advances in medical science and health information, independent professional verifica tion of medical diagnoses, indications, appropriate pharmaceutical selections and dosages, and treatment options should be made and healthcare professionals should consult a variety of sources. When prescribing medication, healthcare professionals are advised to consult the product information sheet (the manufacturer’s package insert) accompanying each drug to verify, among other things, conditions of use, warnings, and side effects and identify any changes in dosage schedule or contraindications, particularly if the medication to be administered is new, infrequently used, or has a narrow therapeutic range. To the maximum extent permitted under applicable law, no responsibility is assumed by the publisher for any injury and/or damage to persons or property, as a matter of products liability, negligence law or otherwise, or from any reference to or use by any person of this work. shop.lww.com

To my wonderful wife, Sara, an essential partner at home and at work—we continue to make a perfect team; our children Michael and Patrick, our daughter-in-law Erin, our grandchild Emma, Daniel, Megan, and our soon to be son-in-law Brendan, for al ways reminding me what is important in life; my mother, Cathie and the memory of my father Al, for all their love and support over the years; and my brothers, sisters-in-law, brothers-in-law, and their children, and my parents-in-law, who demonstrate how essential family really is in our lives.

About the Series

T he beauty of the atlas/synopsis concept is the powerful combination of illustrative photographs and a summary approach to the text. Ophthalmology is a very visual discipline that lends itself wonderfully to clinical photographs. Whereas the seven ophthalmic subspecialties in this series—Cornea, Retina, Glaucoma, Oc uloplastics, Neuro-ophthalmology, Uveitis, and Pediatrics—employ varying levels of visual rec ognition, a relatively standard format for the text is used for all volumes.

The goal of the series is to provide an up-to-date clinical overview of the major areas of ophthalmology for students, residents, and practitioners in all the health care professions. The abundance of large, excellent-quality pho tographs (both in print and online) and con cise, outline-form text will help achieve that objective.

Christopher J. Rapuano Series Editor

Preface

T he main objective of basic ophthalmic education is to train the user to discover the full history of the patient’s illness, rec ognize the abnormal physical signs, make a diagnosis, and suggest appropriate methods of treatment. The aim of higher training is to amplify these capabilities in breadth and depth through practical experience and sub specialty training. During case presentations and even clinical examinations, it is common to encounter trainees making the wrong diag nosis and arriving at the wrong treatment plan. There are two primary reasons for this error. First, they may fail to detect all the abnormal signs, and second, they are unable to integrate and interpret the facts that are collected. The first step in the management of any condition is making a correct diagnosis. One must be able to detect all the abnormal signs and know what one is observing. The goal of this book is to use color photo graphs of the important corneal, anterior seg ment, and external diseases with outline-form text to succinctly illustrate and describe these conditions. This atlas is intended not only for ophthalmic residents and cornea fellows but also for practicing physicians. Each sec tion covers the clinical features of important cornea and external eye diseases, differential

diagnoses, diagnostic tests, and treatment op tions. In addition to providing practical infor mation on the approach to and management of each condition, this book aids recognition of clinical signs by including a selection of clas sic photographs. In the field of cornea, the old adage “A picture is worth a thousand words” is woefully inadequate because not even a thou sand words can substitute for a good picture of a condition. It is hoped that the extensive use of color photographs throughout this af fordable atlas, augmented by hundreds of ad ditional photos online, will have a great impact on the memory and facilitate learning. To emphasize the importance of sign rec ognition and the powers of observation, the following quotations may serve as useful re minders for all of us: Credit must be given to observation rather than theories, and to theories only in so far as they are confirmed by the observed facts. Aristotle The more I see, the more I see there is to see. John Sebastian

Christopher J. Rapuano Editor

vii

Acknowledgments

I would like to acknowledge the many people who helped make this book a reality. Most of the clinical photographs came from my patients. I am grateful to them for allowing me to subject them to flash photography. Several colleagues generously supplied additional photographs, including Elisabeth Cohen, MD, Peter Laibson, MD, Irving Raber, MD, Wee-Jin Heng, MD, Beeran Meghpara, MD, and also Rolande Mi chaud, MD, via Patricia Laughrea, MD, from Quebec, Canada. I would also like to thank all my colleagues at Wills Eye Hospital over the years for their friendship and support and for trusting many of their patients to my care. I also thank Jack Scully, Roger Barone, and Bill Romano of the Media Technology

Department at Wills Eye for all their help and expertise with the photographic needs for this book and for all the volumes in this series and for keeping Wills Eye Hospital on the fore front of the technology revolution. I wish to thank Christopher Teja, Eric McDermott, and Venugopal Loganathan and the team at Wolters Kluwer for giving me the opportunity to be a part of this series and for keeping the process moving forward. Finally, I thank all of our clinical and re search fellows and residents at Wills Eye Hospital, past and present, for all they do to encourage me to continue teaching and learn ing in our wonderful subspecialty of cornea and anterior segment disease.

viii

Contents

About the Series vi Preface vii Acknowledgments viii

Chapter 1 Conjunctival Infections and Inflammations 2 Blepharitis and Meibomitis 2 Chalazion (Internal Hordeolum, Stye) 4 Bacterial Conjunctivitis (Nongonococcal) 6 Gonococcal Bacterial Conjunctivitis 8 Viral Conjunctivitis (Typically Adenovirus) 10 Chlamydial Conjunctivitis (Adult Inclusion Conjunctivitis) 14 Trachoma 16

Molluscum Contagiosum 18 Ligneous Conjunctivitis 20 Pediculosis 22 Parinaud Oculoglandular Syndrome 24 Ophthalmia Neonatorum 26 Allergic Conjunctivitis 28

Atopic Keratoconjunctivitis 30 Vernal Keratoconjunctivitis 32 Superior Limbic Keratoconjunctivitis 36 Floppy Eyelid Syndrome 38 Toxic and Factitious Keratoconjunctivitis (Keratitis Medicamentosa) 42 Ocular Rosacea 46

Chapter 2 Conjunctival Degenerations and Mass Lesions 48 Pingueculae and Pterygium 48 Other Conjunctival Degenerations 52 Amyloidosis 52 Calcium Concretions 52 Melanocytic Conjunctival Lesions 54 Conjunctival Epithelial Melanosis (Racial Melanosis) 54 Oculodermal Melanosis (Nevus of OTA) 54 Nevus 54

Primary Acquired Melanosis 54 Secondary Acquired Melanosis 55 Malignant Melanoma 55 Benign Amelanocytic Conjunctival Lesions 58 Granulomas 58 Epibulbar Dermoid 58

x Contents

Lipodermoid 58 Hereditary Benign Intraepithelial Dyskeratosis 58 Potentially Malignant Amelanocytic Conjunctival Lesions 64 Squamous Papilloma 64 Conjunctival Intraepithelial Neoplasia 64 Squamous Cell Carcinoma 64 Other Carcinomas 64 Reactive Lymphoid Hyperplasia and Non-Hodgkin Lymphoma 65 Cystic Lesions 70 Primary Conjunctival Cyst 70 Iatrogenic Cysts 70 Vascular Lesions 72 Telangiectasias 72 Hematologic Disorders 72 Hemorrhagic Lymphangiectasia 72 Capillary Hemangioma 72 Lymphangioma 72 Kaposi Sarcoma 72 Sturge–Weber Syndrome (Encephalotrigeminal Angiomatosis) 72 Carotid–Cavernous Sinus and Dural–Sinus Fistulas 73

Chapter 3 Anterior Segment Developmental Anomalies 76 Anomalies of Corneal Size and Shape 76

Microcornea 76 Megalocornea 78

Nanophthalmos 80 Microphthalmos 80 Buphthalmos 82 Congenital Anterior Staphyloma and Keratectasia 84

Sclerocornea 86 Cornea Plana 88 Anterior Segment Dysgeneses 90 Posterior Embryotoxon 90 Axenfeld–Rieger Syndrome 90 Peters Anomaly 90 Localized Posterior Keratoconus 90 Aniridia 96 Iris Coloboma 100 Chapter 4 Ectatic Conditions of the Cornea 102 Keratoconus 102 Pellucid Marginal Degeneration 114 Keratoglobus 118

Contents xi

Chapter 5 Corneal Dystrophies 120 Anterior Corneal Dystrophies 120

Epithelial Basement Membrane Dystrophy (Anterior Basement Membrane Dystrophy, Map-Dot-Fingerprint Dystrophy, Cogan Microcystic Dystrophy) 120 Meesmann Corneal Dystrophy (Juvenile Hereditary Epithelial Dystrophy) 128 Lisch Corneal Dystrophy 130 Reis–Bücklers and Thiel–Behnke Corneal Dystrophies 132 Gelatinous Drop–Like Corneal Dystrophy 138 Stromal Corneal Dystrophies 140 Granular Corneal Dystrophy, Type I 140 Lattice Corneal Dystrophy 148 Granular Corneal Dystrophy, Type II 156

Macular Corneal Dystrophy 164 Schnyder Corneal Dystrophy 170 Posterior Corneal Dystrophies 174 Fuchs Endothelial Corneal Dystrophy 174

Posterior Polymorphous Corneal Dystrophy 182 Congenital Hereditary Endothelial Dystrophy 186 Chapter 6 Corneal Degenerations and Deposits 188 Involutional Changes 188 Corneal Arcus 188 White Limbal Girdle of Vogt 188 Crocodile Shagreen 188 Cornea Farinata 189 Polymorphic Amyloid Degeneration 189 Corneal Deposits—Nonpigmented 194 Band Keratopathy 194 Salzmann Nodular Degeneration 198 Other Corneal Degenerations 202 Spheroidal Degeneration 202

Lipid Keratopathy 202 Coats White Ring 202 Corneal Deposits—Pigmented 206 Cornea Verticillata (Vortex Keratopathy) 206

Crystalline Keratopathy 208 Corneal Iron Deposits 212 Kayser–Fleischer Ring 216 Terrien Marginal Degeneration 218 Iridocorneal Endothelial Syndrome 220

xii Contents

Chapter 7 Corneal Infections, Inflammations, and Surface Disorders 222 Bacterial Keratitis 222 Fungal Keratitis 228

Acanthamoeba Keratitis 232 Herpes Simplex Keratitis 236

Primary Ocular Herpes 236 Recurrent Ocular Herpes Simplex 238 Herpes Zoster Keratitis 250 Interstitial Keratitis (Syphilitic, Nonsyphilitic) 256 Subepithelial Infiltrates 260 Superficial Punctate Keratopathy (Punctate Epithelial Erosions) 262

Thygeson Superficial Punctate Keratopathy 264 Dry Eye Syndrome (Keratoconjunctivitis Sicca) 266 Filamentary Keratopathy 270 Exposure Keratopathy 272 Neurotrophic Keratopathy 274 Recurrent Corneal Erosion 276 Bullous Keratopathy 280 Acquired Immunodeficiency Syndrome 284 Contact Lens Complications 286

Toxic/Allergic Conjunctivitis 286 Giant Papillary Conjunctivitis 286 Contact Lens Keratopathy (Contact Lens–Associated Superior Limbic Keratoconjunctivitis and Limbal Stem Cell Deficiency) 286 Contact Lens Overwear Syndrome 287 Tight Lens Syndrome 287 Corneal Warpage 287 Corneal Neovascularization 287 Sterile Keratitis 288 Microbial Keratitis 288 Chapter 8 Systemic and Immunologic Conditions Affecting the Cornea 294 Wilson Disease (Hepatolenticular Degeneration) 294 Vitamin A Deficiency 296 Cystinosis 298 Mucopolysaccharidoses and Lipidoses 300 Collagen Vascular Diseases 302 Ocular Mucous Membrane Pemphigoid 308 Stevens–Johnson Syndrome (Erythema Multiforme Major) 312

Mooren Ulcer 316 Phlyctenulosis 318 Staphylococcal Hypersensitivity 320 Corneal Graft Rejection 322

Contents xiii

Chapter 9 Anterior Sclera and Iris 328 Episcleritis 328 Anterior Scleritis (Noninfectious) 332 Iris Cysts 338 Iris Pigment Epithelial Cyst 338 Iris Stromal Cyst 338 Iris Tumors 340 Iris Nevus 340 Malignant Melanoma 340 Metastatic Tumor 340 Vascular Tumor 340 Chapter 10 Surgery and Complications 342

Cataract Extraction and Intraocular Lens Implantation 342 Full-Thickness Corneal Transplantation (Penetrating Keratoplasty) 346 Endothelial Keratoplasty 354 Anterior Lamellar Keratoplasty 360 Corneal Biopsy 364 Superficial Keratectomy 366 Excimer Laser Phototherapeutic Keratectomy 368 Conjunctival Flap 372

Limbal Stem Cell Transplantation 376 Amniotic Membrane Transplantation 378

Corneal Perforation 382 Refractive Surgery 384

Chapter 11 Trauma 396 Chemical Burns 396

Thermal and Electrical Burns 402 Thermal Burns 402 Electrical Burns 404 Ultraviolet Keratopathy (Arc Welder Flash) 404 Corneal Abrasion 406 Corneal and Conjunctival Foreign Bodies 410 Subconjunctival Hemorrhage 414 Corneoscleral Laceration and Wound Dehiscence 416 Traumatic Hyphema 424

Epithelial Downgrowth 426 Descemet Detachment 430

Index 433

COLOR ATLAS & SYNOPSIS OF Clinical Ophthalmology Wills Eye Hospital

Cornea FOURTH EDITION

CHAPTER

Ectatic Conditions of the Cornea 4

KERATOCONUS K eratoconus is a fairly common condition characterized by corneal thinning, pro trusion, and irregularity. It is almost always bilateral, although the severity of involvement is often asymmetric. Etiology ● Sporadic or autosomal dominant with in complete penetrance ● Gradually decreasing vision, typically be ginning in adolescence and progressing into adult life ● Patients often relate a history of not being able to attain good vision despite multiple changes of glasses or soft contact lenses. ● May have a history of eye rubbing or fist pushing into eye while sleeping ● Can develop acutely decreased vision and pain due to hydrops with advanced disease ● Eye rubbing Symptoms

Signs ● Earlier ■ Progressive myopia and astigmatism

■ Scissors reflex on retinoscopy ■ Irregular mires on keratometry

■ Inferior steepening on computed corneal topography ( Fig. 4-1A ) and tomography ( Fig. 4-1B and C ). Eyes with “low-sagging cones” can demonstrate a mild crab-claw topographic pattern ( Fig. 4-1D ), which is similar to the pattern seen in pellucid marginal degeneration. ■ Central or paracentral stromal thinning of the cornea with the greatest protrusion at the apex of the thinning ( Fig. 4-1E , eFig. 4-1E) ■ Epithelial thinning at the apex of the cone often with surrounding epithelial thickening in a “doughnut” shape seen on imaging, such as anterior segment optical coherence tomography (Fig. 4-1F) ■ Fleischer ring: epithelial iron deposition at the base of the cone ( Fig. 4-1G ) ■ Prominent corneal nerves ( Fig. 4-1H )

102

Keratoconus 103

● Later ■ Vogt striae: fine vertical deep stromal tension lines that disappear temporarily with digital pressure applied to the limbus ( Fig. 4-1I) ■ Abnormal “oil droplet” red reflex ■ Rizzuti sign: conical light reflection on the nasal limbus when light is shone from the temporal side ■ Variable corneal scarring, depending on severity ( Fig. 4-1J–O ). May develop an ele vated apical nodule ( Fig. 4-1P, eFig. 4-1I–L) ■ Munson sign: bulging of the lower eyelid in downgaze ■ Acute hydrops: severe corneal edema resulting from a tear in Descemet mem brane ( Fig. 4-1Q–U, eFig. 4-1P and Q) Associated Problems ● Ocular: vernal disease, blue sclera, retinitis pigmentosa, Leber congenital amaurosis, floppy eyelid syndrome ● Systemic: Down syndrome, sleep apnea, Ehlers–Danlos syndrome, Apert syndrome, ocular allergies, osteogenesis imperfecta Differential Diagnosis ● Pellucid marginal degeneration: inferior peripheral corneal thinning with protrusion of the cornea above the area of maximal thinning Treatment ● Mild cases: glasses and soft contact lenses ● Moderate cases: rigid gas-permeable con tact lens (RGPCL), hybrid lens, or scleral lens ● Severe and contact lens–intolerant cases: ■ Lamellar keratectomy with a blade or excimer laser for anterior nodules ■ Placement of intracorneal ring segments ■ Corneal stromal addition procedure ■ Deep anterior lamellar keratoplasty ■ Penetrating keratoplasty ■ Epikeratoplasty and thermokeratoplasty are rarely performed.

■ Refractive surgery in patients with keratoconus is unpredictable and generally not recommended, except under special protocols. ● Acute hydrops: generally resolves on its own over weeks to months ■ Sodium chloride 5% drops q.i.d. and/or sodium chloride 5% ointment once daily to q.i.d. ■ Photophobia may be helped by cycloplegia (e.g., cyclopentolate 1% t.i.d.). ■ Consider an aqueous suppressant if intraocular pressure is somewhat elevated (e.g., brimonidine 0.1% b.i.d. to t.i.d.). ■ Intracameral air, or nonexpansile concen trations of SF 6 or C 3 F 8 , may be helpful in resolving edema more quickly than medical therapy alone but has risks, including elevated intraocular pressure and cataract formation. ■ Full-thickness corneal suturing in an attempt to close the gap in Descemet mem brane may be helpful in resolving edema more quickly than medical therapy alone but has risks, including persistent leaking from the suture tracks. ● Corneal cross-linking: indicated for pro gressive disease in eyes with sufficient corneal thickness and minimal to no corneal scarring with the objective of halting progression. Gen erally performed by placing riboflavin drops on the cornea and then treating the cornea with ultraviolet light to “strengthen” the cornea to prevent worsening of keratoconus. Approved by the U.S. Food and Drug Administration to treat progressive keratoconus and postrefrac tive surgery ectasia. Short- and medium-term results are promising for stopping progres sion. Best results are obtained when treating keratoconus at a relatively early stage. Prognosis ● Most patients do well with RGPCLs or scleral lenses. Corneal cross-linking is usually successful at preventing progression. The success rate with corneal transplantation in keratoconus is high.

104 4 Ectatic Conditions of the Cornea

FIGURE 4-1. Keratoconus corneal topography. A. Significant irregular inferior corneal steepening is apparent using computed corneal topographic analysis in an eye with moderate keratoconus. As seen on the color scale on the left, the red colors indicate corneal steepening, and blue colors indicate corneal flattening. The figure on the right shows the Placido rings; this image is important to verify the quality and centration of the study. B. A tomo graphic (Pentacam) map of the right eye of a patient with keratoconus. This display includes the anterior sagittal curvature, corneal thickness, and the anterior and posterior elevation maps. Note the irregular inferior steepening on the anterior curvature map, the abnormally thin and slightly inferiorly displaced area of thinnest cornea on the corneal thickness map, and the abnormal anterior and posterior elevations, all consistent with keratoconus.

Keratoconus 105

D FIGURE 4-1. ( continued ) C. The Belin/Ambrósio Enhanced Ectasia Display of the eye seen in B demonstrating significantly abnormal anterior and posterior elevations, highly suggestive of keratoconus. The “D value” in the lower right corner of the display is 8.51; above 2.0 is considered abnormal. D. The irregular inferior steepening seen on computed corneal topographic analysis of an eye with keratoconus revealing a slight crab-claw pattern, which is reminiscent of pellucid marginal degeneration. Eyes with “low-sagging cones” can demonstrate this topo graphic pattern.

106 4 Ectatic Conditions of the Cornea

FIGURE 4-1. ( continued ) Keratoconus E. Anterior segment optical coherence tomography pachymetry map of an eye with keratoconus. The color image on the left depicts the total corneal thickness displaying a thinner-than normal cornea with slight inferior decentration of the thinnest point, which is typical of keratoconus. The color image on the right is just the epithelial thickness demonstrating a relatively thin epithelium centrally with a thick ened epithelium in the midperiphery, the so-called “doughnut effect.” F. Slit-beam view of an eye with significant keratoconus demonstrating inferocentral corneal thinning and steepening. Note the thinnest and most protruded areas of cornea coincide.

Keratoconus 107

FIGURE 4-1. ( continued ) G. A prominent Fleischer ring, iron pigment deposition at the base of the cone, is present in an eye with keratoconus . H. Prominent corneal nerves can be seen in an eye with keratoconus. These nerves can be distinguished from corneal “ghost” blood vessels because “ghost” vessels have a lumen, making them appear as two parallel lines.

108 4 Ectatic Conditions of the Cornea

FIGURE 4-1. ( continued ) I. Faint, vertical posterior stromal stress lines, Vogt striae, are visible at the apex of the cone. Gentle pressure on the limbus can cause these lines to change direction or disappear. J. Significant central stromal scarring is present in an eye with advanced keratoconus.

Keratoconus 109

FIGURE 4-1. ( continued ) K. Central corneal scarring and a prominent Fleischer ring are seen in the left eye with keratoconus. L. The same eye with keratoconus seen in K demonstrating severe corneal stromal thinning. M. Anterior segment optical coherence tomography of the cornea with keratoconus seen in K and L clearly illustrating the severe central corneal stromal thinning. There is substantial overlying epithelial thickening, termed compensa tory epithelial hyperplasia .

110 4 Ectatic Conditions of the Cornea

FIGURE 4-1. ( continued ) N. Moderate inferocentral corneal scarring can be seen in an eye after resolution of corneal hydrops. An iron line is visible at the superior edge of the scarring. O. Slit-beam image of the same eye demonstrating significant thinning in the area of scarring.

Keratoconus 111

FIGURE 4-1. ( continued ) P. A hypertrophic nodule is present at the apex of the cone. These nodules can occur de novo or related to rigid contact lens wear. Such a nodule can affect vision and/or interfere with comfortable contact lens wear. These nodules can be removed with a superficial keratectomy with a blade or excimer laser phototherapeutic keratectomy. Q. Acute corneal hydrops occurs when the cornea stretches to such a degree that a tear develops in Descemet membrane, allowing a sudden inflow of aqueous fluid into the corneal stroma. The corneal stroma can swell to greater than five times its normal thickness. Acute hydrops are associated with a sudden decrease in vision and an increase in pain.

112 4 Ectatic Conditions of the Cornea

FIGURE 4-1. ( continued ) R. Slit-beam view of the same cornea seen in Q. Note the severe corneal thickening. A prominent cleft is apparent centrally, where corneal lamellae are separated by a large degree of aqueous fluid. S. Severe corneal whitening from acute corneal hydrops is present. The fellow eye has scarring from previous cor neal hydrops (see N and O ).

Keratoconus 113

FIGURE 4-1. ( continued ) T. This eye with keratoconus has severe corneal edema due to acute hydrops. U. Slit-beam photograph of the eye in T demonstrating extensive protrusion and massive corneal edema/thickening from the acute hydrops.

114 4 Ectatic Conditions of the Cornea

PELLUCID MARGINAL DEGENERATION P ellucid marginal degeneration is an uncommon, bilateral condition with inferior corneal thinning, protrusion, and ir regularity. It usually presents in early to middle adulthood.

Differential Diagnosis ● Keratoconus: inferocentral corneal thinning with protrusion of cornea in the area of great est thinning. A Fleischer ring and Vogt striae may be present. Treatment ● Mild and moderate cases: RGPCL, hybrid lens, or scleral lens ● Severe and contact lens–intolerant cases ■ Deep anterior lamellar keratoplasty ■ Large inferiorly displaced penetrating keratoplasty ■ Inferior crescentic wedge resection ■ Crescentic penetrating keratoplasty (sometimes followed by a central pen etrating keratoplasty) and placement of intracorneal ring segments are occasionally performed. ■ Corneal collagen cross-linking can be considered but is generally not as success ful as when treating keratoconus. ■ Refractive surgery in patients with pellu cid marginal degeneration is unpredictable and generally not recommended. ● Acute hydrops: see section on Keratoconus earlier Prognosis ● Most patients do well with RGPCLs, al though they are harder to fit than in patients with keratoconus. Patients can also do very well with scleral lenses. The success rate with corneal transplantation in pellucid marginal degeneration is good, but not as good as kera toconus, because of more peripheral disease.

Etiology ● Sporadic Symptoms

● Gradually decreasing vision beginning in young to middle adulthood. Can develop acute decreased vision and pain due to hy drops with advanced disease Signs ● High irregular against-the-rule astigmatism (flat at 90 degrees, steep at 180 degrees) ● Recognizable “crab-claw” pattern of irregu lar astigmatism on computed corneal topog raphy and tomography ( Fig. 4-2A ), although a similar pattern can be found in eyes with keratoconus with “low-sagging cones” ● Inferior, crescent-shaped band of peripheral corneal thinning, 1 to 2 mm in width, ex tending from the 4 to the 8 o’clock positions, which is separated from the limbus by normal thickness cornea ( Fig. 4-2B , eFig. 4-2B) ● The area of greatest protrusion is located above the band of thinning ( Fig. 4-2C and D ). ● Fleischer ring and Vogt striae are absent. ● Corneal hydrops can occur on rare occa sions ( Fig. 4-2E and F , eFig 4-2E).

Pellucid Marginal Degeneration 115

FIGURE 4-2. Pellucid marginal degeneration corneal topography. A. Significant irregular nasal and tempo ral corneal steepening is apparent in the computed corneal topographic analysis of an eye with moderate pellucid marginal degeneration. Classically, the steepening is seen to curve around inferiorly in this condition. As seen on the color scale on the left, the red colors indicate corneal steepening, and blue colors indicate corneal flattening. The figure on the right shows Placido rings; this image is important to verify the quality and centration of the study. Note the severe distortion of the Placido rings in this eye, with pellucid marginal degeneration. Pellucid marginal degeneration. B. Side view demonstrating corneal protrusion inferiorly with significant steepening near the limbus.

116 4 Ectatic Conditions of the Cornea

FIGURE 4-2. ( continued ) C. Slit-beam photo revealing inferior corneal thinning approximately 2 mm from the limbus, below the area of maximal protrusion. D. Slit-beam view of this eye with severe pellucid marginal degen eration also revealing corneal thinning approximately 2 mm from the inferior limbus. There is significant corneal steepening inferiorly. Note that the most protruded portion of the cornea is above the thinnest area.

Pellucid Marginal Degeneration 117

FIGURE 4-2. ( continued ) E. Severe inferior corneal stromal edema resulting from an episode of acute hydrops related to pellucid marginal degeneration. F. Slit-beam view of the eye seen in E highlights the severe corneal stromal edema from the acute hydrops.

118 4 Ectatic Conditions of the Cornea

KERATOGLOBUS K eratoglobus is an extremely rare, bilateral condition of severe uniform peripheral or diffuse corneal thinning. It usually presents at or shortly after birth. Etiology ● Unknown Symptoms ● Poor vision, occasionally pain due to ● Total corneal thinning with maximal thinning in the midperiphery, resulting in protrusion of the entire cornea ( Fig. 4-3 ). ● The cornea can be very thin. ● Normal corneal diameter; very deep anterior chamber ● Acute hydrops may occur in advanced cases. hydrops Signs

● Patient may develop a corneal perforation from minimal trauma because of the severe corneal thinning. Associated Problems ● A syndrome comprising blue sclera, hyperextensible joints, dental and hearing abnormalities ● Ehlers–Danlos type VI ● Rubinstein–Taybi syndrome Treatment ● Mild and moderate cases: spectacles, which improve vision and provide some protection against trauma ● Severe cases: Some patients do well with a scleral lens. ● Surgical treatment is problematic. A large tectonic lamellar graft followed many months later by a smaller penetrating graft is an option. Prognosis ● Fair. Surgical treatment has a low success rate.

Keratoglobus 119

FIGURE 4-3. Keratoglobus. A. A thin, bulging cornea is evident in this eye with keratoglobus. B. Slit-beam view demonstrating that the thinnest portion of the cornea is in the periphery in this eye with keratoglobus.

Ophthalmology

Developed at Philadelphia’s world-renowned Wills Eye Hospital, the Color Atlas and Synopsis of Clinical Ophthalmology series covers the most clinically relevant aspects of ophthalmology in a highly visual, easy-to-use format. Vibrant, full-color photos and a consistent outline structure present a succinct, high-yield approach to the seven topics covered by this popular series: Cornea , Retina , Glaucoma , Oculoplastics , Neuro-Ophthalmology , Pediatrics , and Uveitis . This in-depth yet focused approach makes each volume an excellent companion to the larger Wills Eye Manual as well as a practical stand-alone reference for students, residents, and practitioners in every area of ophthalmology. The updated Cornea volume includes: • Expert guidelines for the differential diagnosis and treatment of cornea diseases seen by the ophthalmic resident, general ophthalmologist, and cornea specialist • Up-to-date information on infections and complications of corneal surgeries • More than 450 high-quality photographs of important corneal, anterior segment, and external diseases, many new and updated for this fourth edition • Revised coverage of the clinical features of key cornea and external eye diseases, diagnostic tests, differential diagnoses, and treatment • Hundreds of additional color images available online to augment the photographs in the text Enrich Your eBook Reading Experience • Read directly on your preferred device(s) , such as computer, tablet, or smartphone. • Easily convert to audiobook , powering your content with natural language text-to-speech. COLOR ATLAS & SYNOPSIS OF Clinical Ophthalmology Christopher J. Rapuano, MD SERIES EDITOR Christopher J. Rapuano, MD Cornea FOURTH EDITION Wills Eye Hospital

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