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The American Academy of Ophthalmology is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. The American Academy of Ophthalmology designates this enduring material for a maximum of 15 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity. CME expiration date: June 1, 2021. AMA PRA Category 1 Credits™ may be claimed only once between June 1, 2018, and the expiration date. BCSC® volumes are designed to increase the physician’s ophthalmic knowledge through study and review. Users of this activity are encouraged to read the text and then answer the study questions provided at the back of the book. To claim AMA PRA Category 1 Credits™ upon completion of this activity, learners must demonstrate appropriate knowledge and participation in the activity by taking the posttest for Section 12 and achieving a score of 80% or higher. For further details, please see the instructions for requesting CME credit at the back of the book. The Academy provides this material for educational purposes only. It is not intended to represent the only or best method or procedure in every case, nor to replace a physician’s own judgment or give speci�c advice for case management. Including all indications, contraindications, side e�ects, and alternative agents for each drug or treatment is beyond the scope of this material. All information and recommendations should be veri�ed, prior to use, with current information included in the manufacturers’ package inserts or other independent sources, and considered in light of the patient’s condition and history. Reference to certain drugs, instruments, and other products in this course is made for illustrative purposes only and is not intended to constitute an endorsement of such. Some material may include information on applications that are not considered community standard, that re�ect indications not included in approved FDA labeling, or that are approved for use only in restricted research settings. The FDA has stated that it is the responsibility of the physician to determine the FDA status of each drug or device he or she wishes to use, and to use them with appropriate, informed patient consent in compliance with applicable law. The Academy speci�cally disclaims any and all liability for injury or other damages of any kind, from negligence or otherwise, for any and all claims that may arise from the use of any recommendations or other information contained herein. AAO, AAOE, American Academy of Ophthalmology, Basic and Clinical Science Course, BCSC, EyeCare America, EyeNet, EyeSmart, EyeWiki, Femtocenter, Focal Points, IRIS, ISRS, OKAP, ONE, Ophthalmic Technology Assessments, Ophthalmology, Ophthalmology Retina, Preferred Practice Pattern, ProVision, The Ophthalmic News & Education Network, and the AAO logo (shown on cover) and tagline (Protecting Sight. Empowering Lives.) are, among other marks, the registered trademarks and trademarks of the American Academy of Ophthalmology. Cover image: End-stage chorioretinal atrophy in pathologic myopia. (Courtesy of Richard F. Spaide, MD.) Copyright © 2018 American Academy of Ophthalmology. All rights reserved. No part of this publication may be reproduced without written permission. Basic and Clinical Science Course Louis B. Cantor, MD, Indianapolis, Indiana, Senior Secretary for Clinical Education Christopher J. Rapuano, MD, Philadelphia, Pennsylvania, Secretary for Lifelong Learning and Assessment George A. Cio�, MD, New York, New York, BCSC Course Chair Section 12 Faculty Colin A. McCannel, MD, Chair, Los Angeles, California Audina M. Berrocal, MD, Miami, Florida Graham E. Holder, PhD, London, United Kingdom Stephen J. Kim, MD, Nashville, Tennessee Brian C. Leonard, MD, Ottawa, Canada Richard B. Rosen, MD, New York, New York Richard F. Spaide, MD, New York, New York Jennifer K. Sun, MD, MPH, Boston, Massachusetts The Academy wishes to acknowledge the American Society of Retina Specialists (ASRS), the Macula Society, and the Retina Society for recommending faculty members to the BCSC Section 12 committee. The Academy also wishes to acknowledge the following committees for review of this edition: Committee on Aging: Amy C. She�er, MD, Houston, Texas Vision Rehabilitation Committee: William M. McLaughlin Jr, DO, Allentown, Pennsylvania Practicing Ophthalmologists Advisory Committee for Education: David J. Browning, MD, PhD, Primary Reviewer, Charlotte, North Carolina; Edward K. Isbey III, MD, Chair, Asheville, North Carolina; Alice Bashinsky, MD, Asheville, North Carolina; Bradley D. Fouraker, MD, Tampa, Florida; Steven J. Grosser, MD, Golden Valley, Minnesota; Stephen R. Klapper, MD, Carmel, Indiana; James A. Savage, MD, Memphis, Tennessee; Michelle S. Ying, MD, Ladson, South Carolina The Academy also wishes to acknowledge the following committee for assistance in developing study questions and answers for this BCSC Section: Self-Assessment Committee: Stephen R. Russell, MD, Iowa City, Iowa; Paul B. Griggs, MD, Seattle, Washington; Rachel M. Huckfeldt, MD, Boston, Massachusetts; Ravi S. J. Singh, MD, Shawnee Mission, Kansas In addition, the Academy wishes to recognize the important contributions of Michael B. Gorin, MD, PhD, in the development of Chapter 13. European Board of Ophthalmology: Catherine Creuzot-Garcher, MD, PhD, EBO Chair, Dijon, France; Peter J. Ringens, MD, PhD, EBO Liaison, Maastricht, Netherlands; Anat Loewenstein, MD, Tel Aviv-Yafo, Israel; Pascale G. Massin, MD, Paris, France; Edoardo Midena, MD, Padua, Italy; Ramin Tadayoni, MD, PhD, Paris, France; Sebastian Wolf, MD, PhD, Bern, Switzerland Financial Disclosures Academy sta� members who contributed to the development of this product state that within the 12 months prior to their contributions to this CME activity and for the duration of development, they have had no �nancial interest in or other relationship with any entity discussed in this course that produces, markets, resells, or distributes ophthalmic health care goods or services consumed by or used in patients, or with any competing commercial product or service. The authors and reviewers state that within the 12 months prior to their contributions to this CME activity and for the duration of development, they have had the following �nancial relationships:* Dr Berrocal: Alcon (C), Allergan (C), Bausch + Lomb (C), Bayer HealthCare Pharmaceuticals (L), DORC Dutch Ophthalmic Research Center (International)/Dutch Ophthalmic USA (L), Visunex Medical Systems (C) Dr Browning: Aerpio Therapeutics (S), Alcon (S), Alimera Sciences (C), Genentech (S), Novartis Pharmaceuticals (S), Ohr Pharmaceutical (S), P�zer (S), Regeneron Pharmaceuticals (S), ZEISS (O) Dr Creuzot-Garcher: Allergan (C, L), Bausch + Lomb (C, L), Bayer (C, L), Novartis Pharmaceuticals (C, L, S), Roche (C), Théa (C, S) Dr Fouraker: Addition Technology (C, L), Alcon (C, L), KeraVision (C, L), OASIS Medical (C, L) Dr Gorin: University of Pittsburgh (P); University of California, Los Angeles (P) Dr Grosser: Injectsense (O), Ivantis (O) Dr Holder: Isarna Therapeutics (C), Roche (C), Servier Laboratories (C) Dr Huckfeldt: Applied Genetic Technologies Corporation (S), Spark Therapeutics (S) Dr Isbey: Alcon (S), Allscripts (C), Bausch + Lomb (S), Med�ow (C), Oculos Clinical Research (S) Dr Klapper: AdOM Advanced Optical Technologies (O) Dr Leonard: Abbott Medical Optics (S), Alcon (S), Allergan (S), Annidis (O), Bausch + Lomb (S), Bayer HealthCare Pharmaceuticals (S), Johnson & Johnson Vision (S), Novartis Pharmaceuticals (S), Ophthalmic Direct (S), Shire (S) Dr Loewenstein: Alcon (C), Allergan (C, L), Bayer (C, L), ForSight Labs (C), Notal Vision (C), Novartis Pharmaceuticals (C, L) Dr Massin: Allergan (C, L), Bayer (C), Novartis Pharmaceuticals (C, L) Dr McCannel: DORC Dutch Ophthalmic Research Center (International)/Dutch Ophthalmic USA (C, L), Genentech (S), Insight Instruments (C), Santen Pharmaceutical (C) Dr Rosen: Allergan (S), Boehringer Ingelheim (C), cellVIEW (C), Clarity Medical Systems (C), Genentech (S), Glauco-Health (C), Guardion Health Sciences (C), Nano Retina (C), Ocata Therapeutics (C), OD- OS (C), Opticology (O), Optovue (C, P), Regeneron Pharmaceuticals (C) Dr Russell: Acucela (S), IDx (O), Spark Therapeutics (C, S), University of Iowa (P) Dr She�er: Allergan (C), Aura Biosciences (S), Genentech (S), Regeneron Pharmaceuticals (S) Dr Spaide: Bausch + Lomb (C), Genentech (C), Topcon Medical Systems (C, P) Dr Sun: Adaptive Sensory Technology (S), Allergan (C), Bayer HealthCare Pharmaceuticals (L), Boston Micromachines Corporation (S), Eleven Biotherapeutics (C), Genentech (S), KalVista Pharmaceuticals (S), Merck & Co. (C), Novartis Pharmaceuticals (C), Optovue (S), Regeneron Pharmaceuticals (C) Dr Tadayoni: Alcon (C, L, S), Alimera Sciences (C, L), Allergan (C, L, S), Bausch + Lomb (C, L), Bayer HealthCare Pharmaceuticals (C, L), Genentech (C), Novartis Pharmaceuticals (C, L, S), ThromboGenics (C), ZEISS (C, L) Dr Wolf: Alcon (C), Allergan (C), Bayer HealthCare Pharmaceuticals (C, L, S), Heidelberg Engineering (C, S), Novartis Pharmaceuticals (C, S), Optos (S), Roche (C) The other authors and reviewers state that within the 12 months prior to their contributions to this CME activity and for the duration of development, they have had no �nancial interest in or other relationship with any entity discussed in this course that produces, markets, resells, or distributes ophthalmic health care goods or services consumed by or used in patients, or with any competing commercial product or service. *C = consultant fees, paid advisory boards, or fees for attending a meeting; L = lecture fees (honoraria), travel fees, or reimbursements when speaking at the invitation of a commercial sponsor; O = equity ownership/stock options of publicly or privately traded �rms (excluding mutual funds) with manufacturers of commercial ophthalmic products or commercial ophthalmic services; P = patents and/or royalties that might be viewed as creating a potential con�ict of interest; S = grant support for the past year (all sources) and all sources used for a speci�c talk or manuscript with no time limitation Recent Past Faculty Neal H. Atebara, MD Emmett Cunningham Jr, MD, PhD, MPH David Sarraf, MD In addition, the Academy gratefully acknowledges the contributions of numerous past faculty and advisory committee members who have played an important role in the development of previous editions of the Basic and Clinical Science Course. American Academy of Ophthalmology Staff Dale E. Fajardo, EdD, MBA Vice President, Education Beth Wilson Daniel Mummert Director, Cont inuing Professional Development Director, Online Edu cation Ann McGuire Jasmine Chen Acquisitions an d Development Manager Manager, E-Lear ning Stephanie Tanaka Eric Gerdes Publications Manage r Interactive De signer D. Jean Ray Donna Scism Production M anager E-Editor/Proof reader Beth Collins Naomi Ruiz Medical Edito r Publications S pecialist Susan Malloy Acquisitions Ed itor and Program Manager American Academy of Ophthalmology 655 Beach Street Box 7424 San Francisco, CA 94120-7424 Contents Title Page Copyright Page Faculty and Disclosures General Introduction Visual Acuity Chart Objectives Introduction PART I Fundamentals and Diagnostic Approaches 1 Basic Anatomy The Vitreous Neurosensory Retina Retinal Topography Retinal Layers and Neurosensory Elements Retinal Vasculature and Oxygen Supply Retinal Pigment Epithelium Bruch Membrane Choroid Sclera 2 Diagnostic Approach to Retinal Disease Ophthalmoscopy Imaging Technologies Fundus Camera Imaging Scanning Laser Ophthalmoscopy Optical Coherence Tomography Optical Coherence Tomography Angiography Fundus Autofluorescence Adaptive Optics Imaging Retinal Angiographic Techniques Ultrasonography 3 Retinal Physiology and Psychophysics Electrophysiologic Testing Electroretinography Full-Field (Ganzfeld) ERG Multifocal ERG Pattern ERG Clinical Considerations Electro-oculography Visual Evoked Cortical Potentials Psychophysical Testing Color Vision Contrast Sensitivity Dark Adaptometry PART II Disorders of the Retina and Vitreous 4 Age-Related Macular Degeneration and Other Causes of Choroidal Neovascularization Age-Related Macular Degeneration Genetics and AMD Nonneovascular AMD Neovascular AMD Other Causes of Choroidal Neovascularization Ocular Histoplasmosis Syndrome Angioid Streaks Pathologic Myopia Idiopathic CNV and Miscellaneous Causes of CNV 5 Retinal Vascular Disease: Diabetic Retinopathy Terminology and Classification Diabetes Terminology Diabetic Retinopathy Terminology Epidemiology of Diabetic Retinopathy Pathogenesis of Diabetic Retinopathy Recommended Diabetes Mellitus–Related Ophthalmic Examinations Systemic Medical Management of Diabetic Retinopathy Abnormalities Associated With Vision Loss From Diabetic Retinopathy Nonproliferative Diabetic Retinopathy Treatment of Nonproliferative Diabetic Retinopathy Proliferative Diabetic Retinopathy Management of Proliferative Diabetic Retinopathy and Its Complications Diabetic Macular Edema Classification of Diabetic Macular Edema Treatment of Diabetic Macular Edema Cataract Surgery in Patients With Diabetes Mellitus 6 Retinal Vascular Diseases Associated With Cardiovascular Disease Systemic Arterial Hypertension Hypertensive Retinopathy Hypertensive Choroidopathy Hypertensive Optic Neuropathy Retinal Vein Occlusion Branch Retinal Vein Occlusion Central Retinal Vein Occlusion Pharmacologic Management of Retinal Vein Occlusion Ocular Ischemic Syndrome and Retinopathy of Carotid Occlusive Disease Symptoms and Signs of Ocular Ischemic Syndrome Etiology and Course of Ocular Ischemic Syndrome Treatment of Ocular Ischemic Syndrome Arterial Occlusive Disease Capillary Retinal Arteriole Obstruction (Cotton-Wool Spots) Branch Retinal Artery Occlusion Cilioretinal Artery Occlusion Paracentral Acute Middle Maculopathy Central Retinal Artery Occlusion Ophthalmic Artery Occlusion Arterial Macroaneurysms 7 Other Retinal Vascular Diseases Sickle Cell Retinopathy Nonproliferative Sickle Cell Retinopathy Proliferative Sickle Cell Retinopathy Other Ocular Abnormalities in Sickle Cell Hemoglobinopathies Management of Sickle Cell Retinopathy Vasculitis Cystoid Macular Edema Etiologies of CME Incidence of CME Treatment of CME Coats Disease Macular Telangiectasia Macular Telangiectasia Type 1 Macular Telangiectasia Type 2 Macular Telangiectasia Type 3 Phakomatoses Von Hippel–Lindau Disease Wyburn-Mason Syndrome Retinal Cavernous Hemangioma Radiation Retinopathy Valsalva Retinopathy Purtscher Retinopathy and Purtscherlike Retinopathy Terson Syndrome 8 Retinopathy of Prematurity Introduction Epidemiology Terminology and Classification Pathophysiology of ROP Natural Course Associated Conditions and Late Sequelae Screening Recommendations Screening Criteria Screening Intervals Fundus Photographic Screening of ROP Prevention and Risk Factors Treatment Laser and Cryoablation Surgery Anti-VEGF Drugs Vitrectomy and Scleral Buckling Surgery 9 Choroidal Disease Central Serous Chorioretinopathy Demographics Imaging Differential Diagnosis Treatment Choroidal Perfusion Abnormalities Arteritic Disease Nonarteritic Disease Choriocapillaris Blood Flow Abnormalities Increased Venous Pressure Age-Related Choroidal Atrophy Choroidal Folds Choroidal Hemangiomas Uveal Effusion Syndrome Bilateral Diffuse Uveal Melanocytic Proliferation 10 Myopia and Pathologic Myopia Prevention The Retina Bruch Membrane Choroidal Neovascularization The Choroid in Pathologic Myopia The Sclera The Optic Nerve 11 Focal and Diffuse Choroidal and Retinal Inflammation Noninfectious Retinal and Choroidal Inflammation White Dot Syndromes Chorioretinal Autoimmune Conditions Sympathetic Ophthalmia Uveitis Masquerade: Intraocular Lymphoma Infectious Retinal and Choroidal Inflammation Cytomegalovirus Retinitis Non-CMV Necrotizing Herpetic Retinitis Endogenous Bacterial Endophthalmitis Fungal Endophthalmitis Tuberculosis Syphilitic Chorioretinitis Cat-Scratch Disease Toxoplasmic Retinochoroiditis Toxocariasis Lyme Disease Diffuse Unilateral Subacute Neuroretinitis West Nile Virus Chorioretinitis Zika Virus Chorioretinitis Ebola Virus Panuveitis Chikungunya Virus Retinitis 12 Congenital and Stationary Retinal Disease Color Vision (Cone System) Abnormalities Congenital Color Deficiency Night Vision (Rod System) Abnormalities Congenital Night-Blinding Disorders With Normal Fundi Congenital Night-Blinding Disorders With Fundus Abnormality 13 Hereditary Retinal and Choroidal Dystrophies Classification General Diagnostic Considerations General Genetic Considerations General Management Considerations Diffuse Dystrophies Diffuse Photoreceptor Dystrophies Choroidal Dystrophies Macular Dystrophies Stargardt Disease Best Disease or Best Vitelliform Dystrophy Adult-Onset Vitelliform Lesions Early-Onset “Drusenoid” Macular Dystrophies Pattern Dystrophies Atypical and “Occult” Macular Dystrophies Inner Retinal Dystrophies X-Linked Retinoschisis 14 Retinal Degenerations Associated With Systemic Disease Retinal Degeneration With Systemic Involvement Infantile-Onset to Early Childhood–Onset Syndromes Bardet-Biedl Syndrome Hearing Loss and Pigmentary Retinopathy: Usher Syndrome Neuromuscular Disorders Other Organ System Disorders Paraneoplastic and Autoimmune Retinopathies Metabolic Diseases Albinism Central Nervous System Metabolic Abnormalities Amino Acid Disorders Mitochondrial Disorders 15 Systemic Drug-Induced Retinal Toxicity Drugs Causing Abnormalities of the Retinal Pigment Epithelium/Photoreceptor Complex Chloroquine Derivatives Phenothiazines Miscellaneous Medications Drugs Causing Occlusive Retinopathy or Microvasculopathy Drugs Causing Ganglion Cell and Optic Nerve Toxicity Drugs Causing Macular Edema Drugs Causing Crystalline Retinopathy Drugs Causing Abnormalities in Color Vision and Electroretinography Miscellaneous Drugs Causing Ocular Toxicities 16 Retinal Detachment and Predisposing Lesions Posterior Vitreous Detachment Examination and Management of Posterior Vitreous Detachment Lesions That Predispose Eyes to Retinal Detachment Lattice Degeneration Vitreoretinal Tufts Meridional Folds, Enclosed Ora Bays, and Peripheral Retinal Excavations Lesions That Do Not Predispose Eyes to Retinal Detachment Paving-Stone Degeneration Retinal Pigment Epithelial Hyperplasia Retinal Pigment Epithelial Hypertrophy Peripheral Cystoid Degeneration Retinal Breaks Traumatic Breaks Trauma in Young Eyes Prophylactic Treatment of Retinal Breaks Symptomatic Retinal Breaks Asymptomatic Retinal Breaks Lattice Degeneration Aphakia and Pseudophakia Fellow Eye in Patients With Retinal Detachment Subclinical Retinal Detachment Retinal Detachment Rhegmatogenous Retinal Detachment Tractional Retinal Detachment Exudative Retinal Detachment Differential Diagnosis of Retinal Detachment Retinoschisis Differentiation of Retinoschisis From Rhegmatogenous Retinal Detachment Macular Lesions Associated With Retinal Detachment Optic Pit Maculopathy Macular Holes in High Myopia 17 Diseases of the Vitreous and Vitreoretinal Interface Posterior Vitreous Detachment Epiretinal Membranes Vitreomacular Traction Diseases Idiopathic Macular Holes Developmental Abnormalities Tunica Vasculosa Lentis Prepapillary Vascular Loops Persistent Fetal Vasculature Hereditary Hyaloideoretinopathies With Optically Empty Vitreous: Wagner and Stickler Syndromes Familial Exudative Vitreoretinopathy Vitreous Opacities Vitreous Degeneration and Detachment Associated Opacities (“Floaters”) Asteroid Hyalosis Vitreous Hemorrhage Pigment Granules Cholesterolosis Amyloidosis Vitreous Abnormalities Secondary to Surgery 18 Posterior Segment Manifestations of Trauma Evaluation of the Patient After Ocular Trauma Blunt Trauma Without Break in Eye Wall Commotio Retinae Choroidal Rupture Posttraumatic Macular Hole Vitreous Hemorrhage Traumatic Chorioretinal Disruption (Retinal Sclopetaria) Open-Globe Injuries Scleral Rupture Lacerating and Penetrating Injuries Perforating Injuries Surgical Management Intraocular Foreign Bodies Posttraumatic Endophthalmitis Prognostication of Globe Injuries Sympathetic Ophthalmia Avulsion of the Optic Nerve Head Abusive Head Trauma Photic Damage Solar Retinopathy Phototoxicity From Ophthalmic Instrumentation Occupational Light Toxicity Handheld Laser-Pointer Injury PART III Selected Therapeutic Topics 19 Laser Therapy for Posterior Segment Diseases Basic Principles of Photocoagulation Choice of Laser Wavelength Practical Aspects of Laser Photocoagulation Complications of Photocoagulation Transpupillary Thermotherapy Photodynamic Therapy Complications of Photodynamic Therapy 20 Vitreoretinal Surgery and Intravitreal Injections Pars Plana Vitrectomy Vitrectomy for Selected Macular Diseases Macular Epiretinal Membranes Vitreomacular Traction Diseases Submacular Hemorrhage Vitrectomy for Vitreous Opacities Vitrectomy for Complications of Diabetic Retinopathy Vitreous Hemorrhage Diabetic Tractional Retinal Detachment Diabetic Macular Edema Vitrectomy for Posterior Segment Complications of Anterior Segment Surgery Postoperative Endophthalmitis Retained Lens Fragments After Phacoemulsification Posteriorly Dislocated Intraocular Lenses Cystoid Macular Edema Suprachoroidal Hemorrhage Needle Penetration of the Globe Rhegmatogenous Retinal Detachment Surgery Techniques for Surgical Repair of Retinal Detachments Outcomes Following Retinal Reattachment Surgery Complications of Pars Plana Vitrectomy Intravitreal Injections Basic Texts Related Academy Materials Requesting Continuing Medical Education Credit Create a Self Test General Introduction The Basic and Clinical Science Course (BCSC) is designed to meet the needs of residents and practitioners for a comprehensive yet concise curriculum of the �eld of ophthalmology. The BCSC has developed from its original brief outline format, which relied heavily on outside readings, to a more convenient and educationally useful self-contained text. The Academy updates and revises the course annually, with the goals of integrating the basic science and clinical practice of ophthalmology and of keeping ophthalmologists current with new developments in the various subspecialties. The BCSC incorporates the e�ort and expertise of more than 90 ophthalmologists, organized into 13 Section faculties, working with Academy editorial sta�. In addition, the course continues to bene�t from many lasting contributions made by the faculties of previous editions. Members of the Academy Practicing Ophthalmologists Advisory Committee for Education, Committee on Aging, and Vision Rehabilitation Committee review every volume before major revisions. Members of the European Board of Ophthalmology, organized into Section faculties, also review each volume before major revisions, focusing primarily on di�erences between American and European ophthalmology practice. Organization of the Course The Basic and Clinical Science Course comprises 13 volumes, incorporating fundamental ophthalmic knowledge, subspecialty areas, and special topics: 1 Update on General Medicine 2 Fundamentals and Principles of Ophthalmology 3 Clinical Optics 4 Ophthalmic Pathology and Intraocular Tumors 5 Neuro-Ophthalmology 6 Pediatric Ophthalmology and Strabismus 7 Orbit, Eyelids, and Lacrimal System 8 External Disease and Cornea 9 Intraocular Inflammation and Uveitis 1 Glaucoma 01 Lens and Cataract 11 Retina and Vitreous 21 Refractive Surgery 3 References Readers who wish to explore speci�c topics in greater detail may consult the references cited within each chapter and listed in the Basic Texts section at the back of the book. These references are intended to be selective rather than exhaustive, chosen by the BCSC faculty as being important, current, and readily available to residents and practitioners. Multimedia This edition of Section 12, Retina and Vitreous, includes videos related to topics covered in the book. The videos were selected by members of the BCSC faculty to present important topics that are best delivered visually. This edition also includes interactive features, or “activities,” developed by members of the BCSC faculty. Both the videos and the activities are available to readers of the print and electronic versions of Section 12 (www.aao.org/bcscvideo_section12 and www.aao.org/bcscactivity_section12). Self-Assessment and CME Credit Each volume of the BCSC is designed as an independent study activity for ophthalmology residents and practitioners. The learning objectives for this volume are given following the Visual Acuity chart. The text, illustrations, and references provide the information necessary to achieve the objectives; the study questions allow readers to test their understanding of the material and their mastery of the objectives. Physicians who wish to claim CME credit for this educational activity may do so by following the instructions given at the end of the book. This Section of the BCSC has been approved by the American Board of Ophthalmology as a Maintenance of Certi�cation Part II self-assessment and CME activity. Conclusion The Basic and Clinical Science Course has expanded greatly over the years, with the addition of much new text, numerous illustrations, and video content. Recent editions have sought to place greater emphasis on clinical applicability while maintaining a solid foundation in basic science. As with any educational program, it re�ects the experience of its authors. As its faculties change and medicine progresses, new viewpoints emerge on controversial subjects and techniques. Not all alternate approaches can be included in this series; as with any educational endeavor, the learner should seek additional sources, including Academy Preferred Practice Pattern Guidelines. The BCSC faculty and sta� continually strive to improve the educational usefulness of the course; you, the reader, can contribute to this ongoing process. If you have any suggestions or questions about the series, please do not hesitate to contact the faculty or the editors. The authors, editors, and reviewers hope that your study of the BCSC will be of lasting value and that each Section will serve as a practical resource for quality patient care.