Pediatric Ophthalmology and Strabismus
Sixth Edition
Christopher J Lyons, MB, FRCS, FRCSC
Professor and Interim Chairman
UBC Department of Ophthalmology and Visual Sciences
Pediatric Ophthalmology and Adult Strabismus
BC Children’s Hospital Vancouver, BC, Canada
Scott R Lambert, MD
Professor of Ophthalmology and Pediatrics
Stanford University School of Medicine
Chief of Ophthalmology
Stanford Children’s Health
Palo Alto, CA, United States
Elsevier
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First edition 1990
Second edition 1997
Third edition 2005
Fourth edition 2013
Fifth edition 2017
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Notices
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ISBN: 978-0-7020-8298-6
E-book: 978-0-7020-8299-3
Video contents, viii
Foreword, x Preface, xi
List of contributors, xii
SECTION I Epidemiology, growth, and development
1 Epidemiology and world-wide impact of visual impairment in children, 1 Jugnoo S Rahi and Clare E Gilbert
2 Clinical embryology and development of the eye, 16 John RB Grigg and Robyn V Jamieson
3 Normal and abnormal visual development, 32 Eileen E Birch and Krista R Kelly
4 Milestones and normative data, 42 Yasmin Bradfield
SECTION II Core practice
5 Examination, history, and special tests in pediatric ophthalmology, 52
G Robert LaRoche
6 Managing refractive errors in children, 63 Amy K Hutchinson and Buddy Russell
7 Pediatric visual electrophysiology – objective measurement of visual function, 72 Dorothy A Thompson, Oliver R Marmoy, and Sian E Handley
8 Imaging the child’s eye, 83 Daniel J Salchow
9 Orbit and visual pathway imaging, 97 Mark Halverson and Anna E Smyth
10 Genetics and pediatric ophthalmology, 107 Panagiotis I Sergouniotis and Graeme CM Black
SECTION III Infections, allergic and external eye disorders
11 Ocular manifestations of intrauterine infections, 114
Christopher Tinley and Lloyd Tooke
12 Conjunctivitis of the newborn, 128
Megan Geloneck and Gil Binenbaum
13 Preseptal and orbital cellulitis, 132
Shirin Hamed Azzam and Jimmy M Uddin
14 Endophthalmitis, 144 Maxwell P Treacy and Donal Brosnahan
15 External eye disease and the oculocutaneous disorders, 150
Stephen J Tuft and Daniel FP Larkin
SECTION IV Systematic pediatric ophthalmology
PART ONE Disorders of the eye as a whole
16 Disorders of the eye as a whole, 179
Sanjana Murali, Faeeqah H Almahmoudi, and Elias I Traboulsi
PART TWO Lids, brows, and oculoplastics
17 Lids: congenital and acquired abnormalities − practical management, 194
Connie Martin Sears, Benjamin P Erickson, and Andrea Lora Kossler
18 The lacrimal system, 210 Mohammad Javed Ali
PART THREE Orbit
19 The management of orbital disease in children, 219 Alan A McNab
20 Vascular diseases of the orbit, 227
Christopher J Lyons and Alan A McNab
21 Neurogenic tumors of the orbit, 242
Peter J Dolman and Yvonne HsiWei Chung
22 Orbital rhabdomyosarcoma, 252
Carol L Shields and Jerry A Shields
23 Other mesenchymal abnormalities, 259
Thomas G Hardy and Alan A McNab
24 Metastatic, secondary, and lacrimal gland tumors, 270
Alan A McNab and Christopher J Lyons
25 Histiocytic, hematopoietic, and lymphoproliferative disorders, 276
Alan A McNab
26 Craniofacial abnormalities, 284
John Lionel Crompton, Joanna Barham Black, and James A Slattery
27 Cystic lesions and ectopias, 301
Alan A McNab
28 Inflammatory disorders, 312
Alan A McNab and Christopher J Lyons
PART FOUR External disease and anterior segment
29 Conjunctiva and subconjunctival tissue, 320 Venkatesh Prajna and Perumalsamy Vijayalakshmi
30 Conjunctival tumors, 327
Jill Razor Wells and Hans E Grossniklaus
31 Anterior segment developmental anomalies, 334
Ken K Nischal
32 Corneal abnormalities in childhood, 351
Stephen J Tuft and Daniel FP Larkin
33 Corneal surgery, 373
Asim Ali and Kamiar Mireskandari
34 The lens, 380
Jay E Self and Ian Christopher Lloyd
35 Childhood cataracts, 390 Scott R Lambert
36 Childhood glaucoma, 407 Alessandra Martins, Maria Papadopoulos, and Sir Peng Tee Khaw
PART FIVE The uvea
37 Pediatric iris disorders, 426
Manoj V Parulekar
38 Aniridia syndrome, 436
Kevin Gregory-Evans and Cheryl Y Gregory-Evans
39 Uveitis, 444
Clive Edelsten
40 Albinism, 468
C Gail Summers
PART SIX Retinal and vitreous disorders
41 Vitreous, 477
Michel Michaelides and Anthony T Moore
42 Retinoblastoma, 492
Christina Stathopoulos and Francis L Munier
43 Retinopathy of prematurity: pathophysiology and screening, 505
Brittni A Scruggs and Michael F Chiang
44 Current treatment of retinopathy of prematurity, 519
Edward H Wood
45 Inherited retinal disorders, 526
Michel Michaelides, Graham E Holder, and Anthony T Moore
46 Retinal dystrophies with systemic associations and the retinal ciliopathies, 550
Hélène Dollfus
47 Inherited macular dystrophies, 566
Michel Michaelides and Anthony T Moore
48 Congenital pigmentary and vascular abnormalities of the retina, 582
Susmito Biswas
49 Retinal flecks, dots, and crystals, 591 Panagiotis I Sergouniotis and Anthony T Moore
50 Acquired and other retinal disorders (including juvenile X-linked retinoschisis), 603
Mary J van Schooneveld and Jan EE Keunen
51 Retinal detachment in childhood, 613
Martin P Snead
PART SEVEN Neural visual systems
52 The pupil, 630
Arko Ghosh, Nita Bhat, and Andrew Go Lee
53 Congenital anomalies of the optic discs, 640
Melinda Y Chang
54 Hereditary optic neuropathies, 650
Jason H Peragallo, Valérie Biousse, and Nancy J Newman
55 Other acquired optic disc abnormalities in children, 661
Stacy Pineles
56 Demyelinating, inflammatory, and infectious optic neuropathies, 668
Gena Heidary
57 The optic chiasm, 676
Michael C Brodsky
58 Headache in children, 688
Shannon J Beres and Grant T Liu
59 Raised intracranial pressure, 695
Robert A Avery
60 The brain and cerebral visual impairment, 700
Lotfi B Merabet and Creig S Hoyt
SECTION V Selected topics in pediatric ophthalmology
61 Delivering bad news, 712
Phoebe Dean Lenhart
62 Common issues arising in children with visual impairment, 718
Carey A Matsuba
63 Visual conversion disorders and fabricated or exaggerated symptoms in children, 724
Susan Mary Carden and William V Good
64 Dyslexia, 731
Sheryl M Handler
65 Neurometabolic disease and the eye, 741
Jane L Ashworth and Andrew AM Morris
66 Leukemia, 757
Richard JC Bowman and Jack Bartram
67 Mitochondrial disorders,767
Luis H Ospina
68 Phakomatoses, 774
John RB Grigg and Robyn V Jamieson
69 Neurofibromatosis type 1 and neurofibromatosis type 2, 787
Robert A Avery
70 Accidental trauma in children, 793
Theodore S Bowe and Ankoor S Shah
71 Child maltreatment, abusive head trauma, and the eye, 808
Patrick Watts
72 Refractive surgery in children, 822
Evelyn A Paysse
SECTION VI Amblyopia, strabismus, and eye movements
PART ONE The fundamentals of strabismus and amblyopia
73 Binocular vision, 830
Eileen E Birch and Anna R O’Connor
74 Amblyopia: the basics, the questions, and the practical management, 838
Michael X Repka
75 Anatomy of strabismus, 846
Joseph L Demer
76 The orthoptic assessment, 858
Darren T Oystreck, Vaishali Mehta, and Leah Walsh
PART TWO Esotropias
77 Infantile esotropias, 871
Glen Gole, Jayne E Camuglia, and Swetha Philip
78 Accommodative esotropias, 885
David R Weakley and Erika Mota Pereira
79 Special esotropias (acute comitant, myopia-associated, and microtropia), 889
Anthony J Vivian and John Somner
PART THREE Exotropias
80 Intermittent exotropia, 896
Seung-Hyun Kim
81 Special forms of comitant exotropia, 906
Gillian GW Adams
PART FOUR Vertical, “pattern” strabismus, and abnormal head posture
82 Vertical strabismus, 914
Burton J. Kushner
83 “A,” “V,” and other pattern strabismus, 926
Burton J Kushner
PART FIVE “Neurological” strabismus
84 Congenital cranial dysinnervation disorders, 936
Ramesh Kekunnaya and Virender Sachdeva
85 Ocular motor nerve palsies, 949
Alexis M Flowers and Jason H Peragallo
86 Myasthenia gravis in children, 959
Jeong-Min Hwang
PART SIX Strabismus treatment
87 Strabismus: non-surgical treatment, 966
Alejandra de Alba Campomanes and Iara Debert
88 Strabismus surgery, 976
David K Coats and Scott E Olitsky
89 Complications in strabismus surgery, 1005
John A Bradbury and Nadeem Ali
PART SEVEN Nystagmus and eye movements
90 Nystagmus in childhood, 1013
Frank Anthony Proudlock and Irene Gottlob
91 Supranuclear eye movement disorders, acquired and neurologic nystagmus, 1026
Richard W Hertle and Nancy N Hanna
SECTION VII Common practical problems in a pediatric ophthalmology and strabismus practice
92 “I think my baby can’t see!”, 1044
Ingele Katinka Casteels
93 “My baby’s got a red eye, Doctor!”, 1049
Giovanni Castano
94 “My child keeps blinking and closing his eye”, 1053
Kimberley Tan
95 “My child seems to hate the bright light”, 1056
Conor Mulholland
96 “My child’s eyes keep watering”, 1060
Anthony G Quinn
97 Proptosis at different ages, 1063
Alan A McNab
98 “My child’s teacher says she can’t see properly”, 1064
Hanne Jensen
99 The child with a dual sensory loss (deafblind), 1068
Nicoline E Schalij-Delfos
100 “My little girl tells me she sees strange things”, 1071
Göran Darius Hildebrand
101 Wobbly eyes in infancy, 1079
Maryam Aroichane
102 Abnormal head postures in children, 1084
Miho Sato
103 Hand defects and the eye, 1088
Luis Carlos Ferreira de Sa and Chong Ae Kim
104 Optimizing compliance in patching therapy, 1095
Christy Giligson and Vaishali Mehta
105 Vision screening, 1099
Evan Silverstein and Sean P Donahue
Index, 1105
Denotes chapters with online video content.
LIST OF CONTRIBUTORS
Gillian GW Adams, MB ChB, FRCSE, FRCOphth
Strabismus and Paediatrics
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Asim Ali, MD, FRCSC
Ophthalmologist-in-Chief
Department of Ophthalmology and Vision Sciences
Hospital for Sick Children; Professor Department of Ophthalmology and Vision Sciences
University of Toronto Toronto, ON, Canada
Mohammad Javed Ali, MD, PhD, FRCS
Professor and Head
Govindram Seksaria Institute of Dacryology
LV Prasad Eye Institute
Hyderabad, Telangana, India; DAAD Professor of Ophthalmology
FAU
Nuremberg, Germany; Hong Leong Professor NUHS
Singapore
Nadeem Ali, MA, MB BChir, FRCSE(Ophth)
Strabismus Service
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Faeeqah H Almahmoudi, MD
Pediatric Ophthalmology Fellow Department of Ophthalmology
King Fahd Armed Forces Hospital
Jeddah, Saudi Arabia; Ocular Genetics
Cole Eye Institute Cleveland, OH, United States
Maryam Aroichane, MD, FRCSC
Clinical Associate Professor Department of Ophthalmology
University of British Columbia Vancouver, BC, Canada
Jane L Ashworth, BM BCh, FRCOphth, PhD
Consultant Paediatric Ophthalmologist
Paediatric Ophthalmology
Manchester Royal Eye Hospital
Manchester University NHS Foundation Trust;
MAHSC Honorary Chair
Faculty of Biology, Medicine and Health University of Manchester Manchester, United Kingdom
Robert A Avery, DO, MSCE
Assistant Professor
Ophthalmology
The Children’s Hospital of Philadelphia Philadelphia, PA, United States
Jack Bartram, MB ChB(Hons), MRCPCH, FRCPath
Consultant Paediatric Haematologist Haematology
Great Ormond Street Hospital for Children NHS Foundation Trust London, United Kingdom
Shannon J Beres, MD
Clinical Assistant Professor Department of Neurology
Child Neurology Division; Clinical Assistant Professor Department of Ophthalmology
Stanford University Palo Alto, CA, United States
Nita Bhat, MD Fellow, Neuro-ophthalmology Department of Ophthalmology
Houston Methodist Hospital Houston, TX, United States
Gil Binenbaum, MD, MSCE
Chief of the Division of Ophthalmology Director, Inpatient Ophthalmology Consultation Service
The Children’s Hospital of Philadelphia; Associate Professor of Ophthalmology
Perelman School of Medicine at the University of Pennsylvania Philadelphia, PA, United States
Valérie Biousse, MD Professor of Neurology and Ophthalmology
Reunette Harris Chair of Ophthalmology
Neuro-Ophthalmology
Emory University School of Medicine Atlanta, GA, United States
Eileen E Birch, PhD
Senior Research Scientist
Pediatric Vision Laboratory
Retina Foundation; Adjunct Professor
Ophthalmology
UT Southwestern Medical Center Dallas, TX, United States
Susmito Biswas, BSc, MB BS, FRCOphth Consultant Paediatric Ophthalmologist
Manchester Royal Eye Hospital
Manchester University NHS Foundation Trust;
Honorary Lecturer in Evolution and Genomic Sciences
School of Biological Sciences
University of Manchester
Manchester, United Kingdom
Graeme CM Black, MA, BM BCh, DPhil, FRCOphth
Professor of Genetics and Ophthalmology
University of Manchester; Honorary Consultant Ophthalmologist and Clinical Geneticist
Manchester Royal Eye Hospital and Manchester Centre for Genomic Medicine
Manchester University NHS Foundation Trust
Manchester, United Kingdom
Joanna Barham Black, MB BS, FRANZCO
Senior Visiting Medical Specialist Department of Ophthalmology; Senior Visiting Medical Specialist
Australian Craniofacial Unit
Adelaide Women’s and Children’s Hospital Adelaide, SA, Australia
Theodore S Bowe, MD
Resident Physician
Ophthalmology
Wills Eye Hospital Philadelphia, PA, United States
Richard JC Bowman, MA, MD, FRCOphth Consultant Ophthalmologist
Great Ormond Street Hospital for Children NHS Foundation Trust
London, United Kingdom
John A Bradbury, FRCS, FRCOphth Ophthalmology
Bradford Royal Infirmary
Bradford, United Kingdom
Yasmin Bradfield, MD
John W Doolittle Professor Department of Ophthalmology and Visual Sciences
University of Wisconsin
Madison, WI, United States
Michael C Brodsky, MD Professor
Ophthalmology and Neurology
Mayo Clinic Rochester, MN, United States
Donal Brosnahan, MB, DCH, FRCOphth
Consultant Ophthalmic Surgeon Royal Victoria Eye and Ear Hospital Dublin, Ireland
Jayne E Camuglia, BSc, MB BS, FRANZCO Department of Ophthalmology
Queensland Children’s Hospital; Ophthalmologist Valley Eye Specialists Brisbane, Qld, Australia
Susan Mary Carden, MB BS, PhD, FRANZCO, FRACS
Associate Professor Department of Paediatrics University of Melbourne; Department of Ophthalmology
Royal Children’s Hospital Melbourne; Department of Ophthalmology
Royal Victorian Eye and Ear Hospital Melbourne, Vic, Australia
Giovanni Castano, MD
Consultant Pediatric Ophthalmologist Department of Ophthalmology
Fundacion Santa Fe de Bogota University Hospital Bogota, Colombia
Ingele Katinka Casteels, MD, PhD Professor Ophthalmology
University Hospitals Leuven Leuven, Belgium
Melinda Y Chang, MD Assistant Professor Department of Ophthalmology Children’s Hospital Los Angeles University of Southern California Los Angeles, CA, United States
Michael F Chiang, MD Director
National Eye Institute
National Institutes of Health Bethesda, MD, United States
Yvonne HsiWei Chung, MB BS, MMED(OPHTH), FAMS Oculoplastics
Singapore National Eye Centre;
Assistant Professor Ophthalmology
Duke NUS Medical School
Singapore
David K Coats, MD Chief of Ophthalmology
Ophthalmology
Texas Children’s Hospital; Professor
Ophthalmology and Pediatrics
Baylor College of Medicine Houston, TX, United States
John Lionel Crompton, MB BS, FRANZCO, FRACS
Clinical Professor School of Medicine
University of Adelaide Adelaide, SA, Australia
Alejandra G de Alba Campomanes, MD, MPH
Professor
Department of Ophthalmology
University of California San Francisco, CA, United States
Iara Debert, MD, PhD
Ophthalmologist
Department of Ophthalmology
Hospital das Clinicas of the University of São Paulo
São Paulo, SP, Brazil
Joseph L Demer, MD, PhD Professor
Ophthalmology
Stein Eye Institute; Professor Neurology
David Geffen Medical School
University of California, Los Angeles; Chief
Pediatric Ophthalmology & Strabismus Division
Stein Eye Institute
University of California, Los Angeles; Arthur L Rosenbaum Chair of Pediatric Ophthalmology
Ophthalmology
Stein Eye Institute
University of California, Los Angeles
Los Angeles, CA, United States
Hélène Dollfus, MD, PhD
Professor Medical Genetics
Strasbourg University Hospital; Coordinator
Centre for Rare Eye Diseases (CARGO)
Strasbourg University Hospital;
Director
Medical Genetics Laboratory
INSERM – University of Strasbourg
Strasbourg, France
Peter J Dolman, MD, FRCSC
Clinical Professor and Division Head (Oculoplastics and Orbit)
Department of Ophthalmology and Visual Sciences
University of British Columbia; Interim Department Head Department of Ophthalmology
Vancouver Acute Hospital
Vancouver, BC, Canada
Sean P Donahue, MD, PhD Professor
Pediatric Ophthalmology
Vanderbilt Eye Institute/VUMC Nashville, TN, United States
Clive Edelsten, MA, FRCOphth Consultant Medical Ophthalmologist
Rheumatology
Great Ormond Street Hospital
London, United Kingdom
Consultant Ophthalmologist
Ophthalmology
Ipswich Hospital
Ipswich, Suffolk, United Kingdom
Benjamin P Erickson, MD
Assistant Clinical Professor
Byers Eye Institute
Stanford School of Medicine
Palo Alto, CA, United States
Luis Carlos Ferreira de Sa, MD Consultant
Pediatrics
Instittuto da Crianca, University of São Paulo Medical School
São Paulo, SP, Brazil
Alexis M Flowers, MD
Neuro-Ophthalmology Fellow
Department of Ophthalmology
Emory University School of Medicine
Atlanta, GA, United States
Megan Geloneck, MD Physician
Pediatric Ophthalmology and Strabismus
Dell Children’s Eye Center
Austin, TX, United States
Arko Ghosh, MD
Resident Physician
Department of Ophthalmology
University of Arizona College of Medicine
Tucson, AZ, United States
Clare E Gilbert, MB ChB, FRCOphth, MD, MSc
Professor of International Eye Health
Department of Clinical Research
London School of Hygiene & Tropical Medicine
London, United Kingdom
Christy Giligson, OC(C)
Senior Teaching Orthoptist Department of Ophthalmology
BC Children’s Hospital Vancouver, BC, Canada
Glen Gole, MB BS, MD, FRANZCO, FRACS, FRCOphth
Professor of Ophthalmology School of Medicine
University of Queensland Brisbane, Qld, Australia
William V Good, MD
Senior Scientist
Ophthalmology
Smith–Kettlewell Eye Research Institute
San Francisco, CA, United States
Irene Gottlob, MD
Professor Department of Neurology Cooper University Hospital Camden, NJ, United States; Neuroscience Psychology and Behaviour University of Leicester Leicester, Leicestershire, United Kingdom
Cheryl Y Gregory-Evans, PhD
Professor
Department of Ophthalmology and Visual Sciences
University of British Columbia Vancouver, BC, Canada
Kevin Gregory-Evans, MD, PhD, FRCS, FRCOphth, FRCSC
Professor Department of Ophthalmology and Visual Sciences
University of British Columbia Vancouver, BC, Canada
John RB Grigg, MB BS, MD, FRANZCO, FRACS
Professor and Head
Specialty of Ophthalmology and Eye Health
The University of Sydney; Consultant Department of Ophthalmology
The Children’s Hospital Westmead, Sydney; Consultant
Ophthalmology
Sydney Eye Hospital
Sydney, NSW, Australia
Hans E Grossniklaus, MD, MBA
Professor of Ophthalmology and Pathology
Ophthalmology
Emory University School of Medicine
Atlanta, GA, United States
Mark Halverson, MD
Paediatric Neuroradiologist
Radiology
British Columbia Children’s Hospital Vancouver, BC, Canada
Shirin Hamed Azzam, MD
Orbital Service
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Sheryl M Handler, MD
Pediatric Ophthalmologist Encino, CA, United States
Sian E Handley, MSc, BMedSci (Hons) Orth
Specialist Clinical Scientist and Orthoptist Clinical and Academic Department of Ophthalmology
Great Ormond Street Hospital for Children NHS Foundation Trust
London, United Kingdom; Clinical Doctoral Research Fellow
Great Ormond Street Institute of Child Health
University College London (UCL) London, United Kingdom
Nancy N Hanna, MD Pediatric Ophthalmologist
Vision Center
Akron Children’s Hospital
Akron, OH, United States;
Clinical Assistant Professor of Surgery
Northeast Ohio Medical University
Rootstown, OH, United States
Thomas G Hardy, MB BS, FRANZCO
Department of Orbital, Plastics and Lacrimal Surgery
Royal Victorian Eye and Ear Hospital
East Melbourne, Vic, Australia; Department of Ophthalmology
Royal Children’s Hospital
Parkville, Vic, Australia; Department of Ophthalmology
Royal Melbourne Hospital; Department of Surgery University of Melbourne
Parkville, Vic, Australia
Gena Heidary, MD, PhD
Director, Pediatric Neuro-ophthalmology Service
Ophthalmology
Boston Children’s Hospital; Assistant Professor Ophthalmology
Harvard Medical School
Boston, MA, United States
Richard W Hertle, MD, FAAO, FACS, FAAP
Director
Vision Center
Akron Children’s Hospital; Chief
Pediatric Ophthalmology
Akron Children’s Hospital
Akron, OH, United States; Professor
Ophthalmology
Northeast Ohio Medical College Rootstown, OH, United States
Göran Darius Hildebrand, MD, MPhil, DCH, FRCS, FRCOphth, FEBO
Consultant Ophthalmic Surgeon Head, Paediatric Ophthalmology Service
Oxford Eye and Children Hospitals
Oxford University Hospitals NHS Trust Oxford, Oxfordshire, United Kingdom
Graham E Holder, BSc, MSc, PhD
Hong Leong Visiting Professor Ophthalmology
Yong Loo Lin School of Medicine
National University of Singapore; Honorary Professor
UCL Institute of Ophthalmology
London, United Kingdom
Creig S Hoyt, MD, MA
Emeritus Professor and Chair Department of Ophthalmology
University of California
San Francisco, CA, United States
Amy K Hutchinson, MD
Professor of Ophthalmology
Emory University School of Medicine; Chief of Ophthalmology
Children’s Healthcare of Atlanta at Egleston
Atlanta, GA, United States
Jeong-Min Hwang, MD Ophthalmology
Soul National University Bundang Hospital Seongnam Republic of Korea
Robyn V Jamieson, MB BS (Hons I), PhD, FRACP, CG(HGSA)
Eye Genetics Research Unit
Children’s Medical Research Institute University of Sydney
The Children’s Hospital at Westmead; Save Sight Institute University of Sydney; Professor Specialty of Genomic Medicine University of Sydney Sydney, NSW, Australia
Hanne Jensen, MD, DMSc Consultant (Retired)
Eye Department
Kennedy Center
Glostrup University Hospital Glostrup, Denmark
Ramesh Kekunnaya, FRCS(Ophthal) Director
Paediatric Ophthalmology, Strabismus & Neuro-Ophthalmology
Child Sight Institute
LV Prasad Eye Institute Hyderabad, India
Krista R Kelly, PhD
Associate Scientist
Vision and Neurodevelopment
Retina Foundation of the Southwest Dallas, TX, United States
Jan EE Keunen, MD, PhD, EBOD Ophthalmology
Radboud University Medical Center Nijmegen, Netherlands
Peng Tee Khaw, PhD, FRCP, FRCS, FRCOphth, FRCPath, FCOptom, Hon DSc, FRSB, FARVO, FMedSci Director
National Institute for Health Research Biomedical Research Centre
Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology; Professor of Glaucoma and Ocular Healing
UCL Institute of Ophthalmology; Department of Glaucoma
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Chong Ae Kim, MD, PhD
Associate Professor and Head of Clinical Genetics
Pediatrics
Faculty of Medicine
University of São Paulo
São Paulo, SP, Brazil
Seung-Hyun Kim, MD, PhD
Professor
Ophthalmology
Korea University College of Medicine
Seoul, Republic of Korea
Andrea Lora Kossler, MD, FACS
Associate Professor
Department of Ophthalmology
Byers Eye Institute at Stanford University
Palo Alto, CA, United States
Burton J Kushner, MD
Professor Emeritus
Department of Ophthalmology and Visual Sciences
University of Wisconsin Madison, WI, United States
Scott R Lambert, MD
Professor of Ophthalmology and Pediatrics
Stanford University School of Medicine; Chief of Ophthalmology
Stanford Children’s Health Palo Alto, CA, United States
Daniel FP Larkin, MD, FRCPI, FRCOphth
Consultant Surgeon
Corneal and External Diseases Service
Moorfields Eye Hospital NHS Foundation Trust; Honorary Professor University College London (UCL) London, United Kingdom
G Robert LaRoche, MD, FRCSC Professor
Ophthalmology and Vision Sciences
Dalhousie University; Division Head
Paediatric Ophthalmology and Oculomotility
IWK Health Centre Halifax, NS, Canada
Andrew Go Lee, MD Chair
Ophthalmology
Houston Methodist Hospital Houston, TX, United States
Phoebe Dean Lenhart, MD
Associate Professor
Ophthalmology
Emory University School of Medicine Atlanta, GA, United States
Grant T Liu, MD
Professor of Neurology and Ophthalmology
Neuro-Ophthalmology Division
Hospital of the University of Pennsylvania and the Children’s Hospital of Philadelphia;
Raymond G Perelman Endowed Chair in Pediatric Neuro-Ophthalmology
Division of Ophthalmology
Children’s Hospital of Philadelphia Philadelphia, PA, United States
I Christopher Lloyd, MB BS, DO, FRCS, FRCOphth
Consultant Paediatric Ophthalmologist
Department of Clinical and Academic Ophthalmology
Great Ormond Street Hospital for Children NHS Foundation Trust
London, United Kingdom; Hon Professor of Paediatric Ophthalmology Ophthalmology
Manchester Academic Health Sciences Centre Manchester, United Kingdom
Christopher J Lyons, MB, DO, FRCS, FRCOphth, FRCSC
Professor and Interim Chairman
Department of Ophthalmology and Visual Sciences
University of British Columbia; Pediatric Ophthalmology and Adult Strabismus
BC Children’s Hospital Vancouver, BC, Canada
Oliver R Marmoy, MSc
Specialist Clinical Scientist
Clinical and Academic Department of Ophthalmology
Great Ormond Street Hospital for Children NHS Foundation Trust; Honorary Research Fellow
Department of Developmental Cancer and Biology
UCL–GOS Institute of Child Health London, United Kingdom
Alessandra Martins, MB BS (Hons), PhD, MRCOphth, FRANZCO
Consultant Ophthalmic Surgeon Department of Glaucoma
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom; Honorary Senior Lecturer
Discipline of Clinical Ophthalmology and Eye Health
University of Sydney
Sydney, NSW, Australia
Carey A Matsuba, BSc, MDCM, MHSc
Clinical Assistant Professor Paediatrics
University of British Columbia Vancouver, BC, Canada
Alan A McNab, FRANZCO, FRCOphth, DMedSc
Consultant
Orbital Plastic and Lacrimal Clinic
Royal Victorian Eye and Ear Hospital East Melbourne, Vic, Australia
Vaishali Mehta, BMedSci (Hons) in Orthoptics
Teaching Orthoptist Ophthalmology and Orthoptics
BC Children’s Hospital Vancouver, BC, Canada
Lotfi B Merabet, OD, PhD, MPH Associate Professor Ophthalmology
Massachusetts Eye and Ear – Harvard Medical School
Boston, MA, United States
Michel Michaelides, BSc, MB BS, MD(Res), FRCOphth, FACS
Consultant Ophthalmic Surgeon Medical Retina and Genetics Moorfields Eye Hospital NHS Foundation Trust; Professor of Ophthalmology Genetics
UCL Institute of Ophthalmology London, United Kingdom
Kamiar Mireskandari, MB ChB, PhD, FRCSE, FRCOphth Professor Department of Ophthalmology and Vision Sciences
University of Toronto; Staff Ophthalmologist Department of Ophthalmology and Vision Sciences
The Hospital for Sick Children Toronto, ON, Canada
Anthony T Moore, MA, FRCS, FRCOphth, FMedSci Emeritus Professor Ophthalmology
University of California, San Francisco San Francisco, CA, United States; Emeritus Professor Institute of Ophthalmology
University College London (UCL) London, United Kingdom
Andrew AM Morris, BM BCh, PhD, FRCPCH
Willink Metabolic Unit
Manchester Centre for Genomic Medicine
Manchester University Hospitals NHS Foundation Trust Manchester, United Kingdom
Conor Mulholland, MB BCh, BAO, FRCSC
Clinical Assistant Professor Department of Ophthalmology and Visual Sciences
University of British Columbia Vancouver, BC, Canada
Francis L Munier, MD Professor
Head of the Department of Ocular Oncology, Pathology, and Oculogenetics
Jules-Gonin Eye Hospital Lausanne, Vaud, Switzerland
Sanjana Murali, BS
Medical Student
School of Medicine
Case Western Reserve University Cleveland, Ohio, United States
Nancy J Newman, MD
LeoDelle Jolley Professor of Ophthalmology, Professor of Ophthalmology and Neurology
Instructor in Neurological Surgery, Director Neuro-Ophthalmology
Emory University School of Medicine Atlanta, GA, United States
Ken K Nischal, MD, FAAP, FRCOphth
Professor and Director
Pediatric Ophthalmology, Strabismus and Adult Motility
Children’s Hospital of Pittsburgh of UPMC Pittsburgh, PA, United States
Anna R O’Connor, PhD, BMedSci(Hons)
Senior Lecturer
School of Health Sciences
University of Liverpool Liverpool, United Kingdom
Scott E Olitsky, MD, MBA
Emeritus Professor of Ophthalmology
University of Missouri - Kansas City School of Medicine
Kansas City, MI, United States
Luis H Ospina, MD
Assistant Professor
Ophthalmology
Ste Justine’s Hospital, University of Montreal Montreal, QC, Canada
Darren T Oystreck, PhD, MMedSci, OC(C), COMT
Chair
Clinical Vision Science Program
Dalnousie University; Professional Practice Leader
Eye Clinic
IWK Health Centre
Halifax, NS, Canada
Maria Papadopoulos, MB BS, FRCOphth
Department of Glaucoma
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Manoj V Parulekar, MS, FRCS, FRCOphth
Consultant Ophthalmologist
Eye Department
Birmingham Children’s Hospital
Birmingham, United Kingdom; Consultant Ophthalmologist
Oxford Eye Hospital
Oxford University Hospitals NHS Trust
Oxford, Oxfordshire, United Kingdom
Evelyn A Paysse, MD Professor
Department of Ophthalmology and Pediatrics
Baylor College of Medicine
Houston, TX, United States
Jason H Peragallo, MD
Associate Professor
Ophthalmology and Pediatrics
Emory University School of Medicine
Atlanta, GA, United States
Erika Mota Pereira, MD
Visiting Assistant Professor
Pediatric Ophthalmology and Strabismus
UT Southwestern Medical Center
Dallas, TX, United States; Consultant Pediatric Ophthalmologist Strabismus
Federal University of Minas Gerais
Belo Horizonte, Minas Gerais, Brazil
Swetha S Philip, MS (Ophthal) Department of Ophthalmology
Queensland Children’s Hospital; Child Health Research Centre
Faculty of Medicine
University of Queensland
Brisbane, Qld, Australia
Stacy Pineles, MD, MS
Associate Professor of Ophthalmology
Ophthalmology
University of California, Los Angeles Los Angeles, CA, United States
Venkatesh Prajna, FRCOphth Department of Cornea
Aravind Eye Hospital Madurai, Tamil Nadu, India
Frank Anthony Proudlock, BSc, MSc, PhD
Associate Professor
Neuroscience, Psychology and Behaviour
University of Leicester Leicester, Leicestershire, United Kingdom
Anthony G Quinn, MB ChB, FRANZCO, FRCOphth, DCH
Paediatric Ophthalmology and Strabismus
West of England Eye Unit
Royal Devon & Exeter NHS Foundation Trust; Consultant Ophthalmologist
Exeter Eye LLP
Exeter, Devon, United Kingdom
Jugnoo S Rahi, MB BS, MSc, PhD, FRCOphth
Professor of Ophthalmic Epidemiology
GOS Institute of Child Health UCL and Institute of Ophthalmology UCL; Consultant Ophthalmologist
Great Ormond Street Hospital NHS Trust
London, United Kingdom
Michael X Repka, MD, MBA
David L Guyton MD and Feduniak Family Professor of Ophthalmology, Professor of Pediatrics
Wilmer Eye Institute
Johns Hopkins University Baltimore, MD, United States
Buddy Russell, COMT, FCLSA, FSLS, LDO
Contact Lens Technologist
Contact Lens
Thomas Eye Group
Atlanta, GA, United States
Virender Sachdeva, MS(Ophth), DNB(Ophth)
Consultant Ophthalmologist
Child Sight Institute, Nimmagada Prasad Children’s Eye Care Centre
Department of Paediatric Ophthalmology, Strabimsus and Neuro-Ophthalmology
LV Prasad Eye Institute
Visakhapatnam, Andhra Pradesh, India
Daniel J Salchow, MD
Professor of Ophthalmology
Ophthalmology
Charité - Universitätsmedizin Berlin Berlin, Germany
Miho Sato, MD, PhD Professor Ophthalmology
Hamamatsu University School of Medicine Hamamatsu, Shizuoka, Japan
Nicoline E Schalij-Delfos, MD, PhD Professor, Pediatric Ophthalmology Department of Ophthalmology
Leiden University Medical Center
Leiden, Netherlands
Brittni A Scruggs, MD, PhD
Assistant Professor
Department of Ophthalmology
Mayo Clinic Rochester, MN, United States
Connie Martin Sears, MD
Ophthalmology
Byers Eye Institute at Stanford Palo Alto, CA, United States
Jay E Self, BM, FRCOphth, PhD
Associate Professor
Vision Sciences
University of Southampton; Consultant Ophthalmologist
Eye Department
University Hospital Southampton Southampton, Hampshire, United Kingdom
Panagiotis I Sergouniotis, FRCOphth, PhD
Senior Lecturer
School of Biological Sciences
University of Manchester; Consultant Ophthalmologist
Manchester Royal Eye Hospital and Manchester Centre for Genomic Medicine
Manchester University NHS Foundation Trust
Manchester, United Kingdom
Ankoor S Shah, MD, PhD
Assistant Professor Department of Ophthalmology
Harvard Medical School; Staff Physician and Surgeon Department of Ophthalmology
Boston Children’s Hospital; Associate Surgeon Department of Ophthalmology
Massachusetts Eye & Ear Boston, MA, United States
Carol L Shields, MD
Director
Ocular Oncology Service
Wills Eye Hospital Philadelphia, PA, United States
Jerry A Shields, MD
Director Emeritus
Ocular Oncology Service
Wills Eye Hospital Philadelphia, PA, United States
Evan Silverstein, MD
Assistant Professor Ophthalmology
Virginia Commonwealth University Richmond, VA, United States
James A Slattery, MB BS, PhD
Ophthalmologist/Oculoplastic Surgeon Department of Ophthalmology
Flinders Medical Centre; Ophthalmologist/Oculoplastic Surgeon Department of Ophthalmology
Women’s and Children’s Hospital Adelaide, SA, Australia
Anna E Smyth, MB BCh, BAO, FFR, RCSI
Paediatric Radiology Fellow
Radiology
BC Children’s Hospital Vancouver, BC, Canada
Martin P Snead, MA, MD, FRCS, DO, FRCOphth
Director of Vitreoretinal Research
University of Cambridge
Van Geest Brain Repair Centre
Cambridge, Cambridgeshire, United Kingdom
John Somner, FRCOphth
Department of Ophthalmology
Cambridge University Hospitals NHS Foundation Trust
Cambridge, Cambridgeshire, United Kingdom
Christina Stathopoulos, MD
Ophthalmology/Pediatric Ocular Oncology
Jules-Gonin Eye Hospital Lausanne, Vaud, Switzerland
C Gail Summers, MD
Emerita Professor
Ophthalmology and Visual Neurosciences
University of Minnesota
MN, United States
Kimberley Tan, MB BS, FRANZCO
Head of Department
Paediatric Ophthalmology
Sydney Children’s Hospital
Randwick; Consultant Neuro-Ophthalmologist
Neuro-Ophthalmology Clinic
Royal North Shore Hospital
St Leonards
Sydney, NSW, Australia
Dorothy Ann Thompson, PhD
Consultant Clinical Scientist
Clinical and Academic Department of Ophthalmology
Great Ormond Street Hospital for Children NHS Foundation Trust
London, United Kingdom
Christopher Tinley, FRCOphth(Lond)
Associate Professor
Division of Ophthalmology
University of Cape Town
Cape Town, Western Cape, South Africa
Lloyd Tooke, MB ChB, MMed(Paeds), FCPaeds, Cert(Neonatology)
Department of Paediatrics, Division of Neonatology
University of Cape Town
Cape Town, Western Cape, South Africa
Elias I Traboulsi, MD, Med
Professor of Ophthalmology
Cole Eye Institute
Cleveland, OH, United States
Maxwell P Treacy, BA, BAI, MB BCh, BAO, MSc, FRCSI, FRCOphth, FEBO
Consultant Ophthalmologist
Vitreoretinal Department
Royal Victoria Eye and Ear Hospital
Dublin, Ireland
Stephen J Tuft, MD, FRCOphth
Professor
Cornea and External Disease
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Jimmy M Uddin, MA, MB BChir, FRCOphth
Adnexal Consultant Ophthalmologist
Moorfields Eye Hospital NHS Foundation Trust
London, United Kingdom
Mary J van Schooneveld, MD, PhD
Ophthalmologist
Ophthalmology Department
Amsterdam University Medical Centre
Amsterdam, Netherlands; Ophthalmologist
Diagnostic Department
Bartiméus
Zeist, Netherlands
Perumalsamy Vijayalakshmi, MS, DO Chief
Paediatric Ophthalmology and Adult Strabismus
Aravind Eye Hospital
Madurai, Tamil Nadu, India
Anthony J Vivian, BSc, MB BS, FRCS, FRCOphth
Consultant Paediatric Ophthalmologist and Adult Strabismus Surgeon
Ophthalmology Department
Cambridge University Hospitals NHS Foundation Trust
Cambridge, Cambridgeshire, United Kingdom
Leah Walsh, MSc, OC(C), COMT
Adjunct Associate Professor
Faculty of Health
Dalhousie University; Orthoptist
Eye Care Team
IWK Health Centre
Halifax, Nova Scotia, Canada
Patrick Watts, MB BS, MS, FRCS, FRCOphth, MSc
Department of Ophthalmology
University Hospital of Wales
Cardiff, United Kingdom
David R Weakley, Jr, MD Professor
Department of Ophthalmology
UT Southwestern Medical Center; Director
Division of Pediatric Ophthalmology
Children’s Health
Dallas, TX, United States
Jill Razor Wells, MD
Assistant Professor Ophthalmology
Emory University
Atlanta, GA, United States
Edward H Wood, MD
Assistant Professor Ophthalmology
Stanford University School of Medicine
Palo Alto, CA, United States
Epidemiology and world-wide impact of visual impairment in children
Jugnoo S Rahi and Clare E Gilbert
CHAPTER CONTENTS
Introduction, 1
Specific issues in the epidemiological study of visual impairment in childhood, 1
Framing the question, 2
Potential sources of information about visual impairment, 3
Impact of visual impairment, 4
Visual impairment in the broader context of child health and childhood disability, 4
INTRODUCTION
This chapter first presents a number of key considerations and issues relevant to understanding and applying evidence from epidemiological studies of childhood visual impairment (VI), severe visual impairment (SVI), or blindness (Box 1.1 and Box 1.2) – collectively “VI” for brevity. Thereafter, the impact of childhood VI is considered from different perspectives. This is followed by consideration of childhood VI in the broader context of child health and childhood visual disability. A synthesis of current epidemiological data, grouped by the GBD super regions, is presented as the key data required for planning clinical services, and for policies. Finally, an overview is presented of primary, secondary and tertiary prevention strategies with consideration of the role of ophthalmic professionals. Areas where critical evidence is lacking are highlighted throughout and potential future directions for research are discussed. Readers are referred to the online extensive supplementary material for a full bibliography.
SPECIFIC ISSUES IN THE EPIDEMIOLOGICAL STUDY OF VISUAL IMPAIRMENT IN CHILDHOOD
• Case definition: A standard definition applicable to all children remains challenging, see below “Who is a visually impaired child?”.
• Rarity: As childhood VI is uncommon, large-scale studies are required to achieve representative samples of affected children for precise and unbiased analysis.
• Complex, multidisciplinary management: For a complete picture, information must be sought from all professionals involved in the
Summary of global frequency and causes of childhood visual impairment, 5
Prevention of visual impairment and blindness in childhood, 12
The role of ophthalmic professionals in prevention of childhood visual impairment, 12
Vision 2020 and universal health coverage, 13
References, 13
care of VI or blind children, as many, in some settings the majority, have additional significant non-ophthalmic impairments or chronic disorders.
• Life course approach: Within child health, life course approaches are now common, to understand the complex interplay between biological, environmental, and lifestyle/social influences at all life stages (preconceptional, prenatal, perinatal, and childhood), and how they combine to set and change health trajectories into adult life. Life course epidemiological and epigenetics approaches are increasingly applied to the study of VI and eye disease affecting children or originating in childhood.1
• Developmental perspectives: In all research on children, developmental issues (as distinct from age-related issues per se) must be taken into account in assessing outcomes and their relationship with risk factors.
• Long-term outcomes: Assessment of meaningful outcomes, such as final visual function or educational placement, requires longterm follow-up, into adult life for some outcomes. This is challenging and is increasingly addressed through data science and health informatics approaches. These use routinely collected data, often as electronic or “e” records, in health care (e.g. personal e health records, EHR/EM) and other health or education or welfare administrative systems with record (data) linkage using established methods to minimize errors to create complete datasets for analysis.2
• Ethics: Issues of proxy consent (by parents) and children’s autonomy increasingly impact participation in ophthalmic epidemiological research.
BOX 1.1 What is ophthalmic epidemiology?
Ophthalmic epidemiology (literally “studies upon people”) has both its origins and its applications in clinical and public health ophthalmology.
The aim of primary or secondary (e.g. systematic literature review, metaanalysis and modeling) research is to:
• provide quantitative information for planning services
• shed light on the causes and natural history of ophthalmic disorders
• enhance the accuracy and efficiency of diagnosis
• improve the effectiveness of treatment and preventive strategies.
BOX 1.2 Epidemiological reasoning
This is based on the following principles:
• the occurrence of disease is not random, rather a balance between causal and protective factors
• that disease causation, modification, and prevention are studied by systematic investigation of populations to gain a more complete view than can be achieved by studying individuals
• that any inference that an association between a risk factor and a disease is causal can only be made after two specific steps in reasoning: (1) the exclusion of chance, bias, or confounding as alternative explanations for the observed association, and (2) evidence of a consistent and strong statistical association, which is biologically plausible, in the correct temporal sequence, and preferably exhibits a dose–response relationship.
FRAMING THE QUESTION
It is useful to think about the evidence needed to make clinical, service provision or policy decisions using a “four-part question” based on the PICO mnemonic Population Intervention/Indicator Comparator and Outcomes). A good question incorporates the reference population (e.g. children under 2 years with infantile esotropia), the risk factor or the intervention and, where appropriate, a comparator (e.g. preterm versus term birth, or strabismus surgery versus no surgery), and the outcomes (e.g. parent-reported improvement in cosmesis and objective improvement in alignment and stereopsis).
The importance of framing the question well lies in the fact that the question will determine the type of study (study design) that can answer it, e.g. a descriptive, cross-sectional prevalence survey, or an analytical study of which of the two broad types are “observational,” e.g. case–control or cohort studies, or “interventional,” e.g. randomized controlled trials.
Who is a visually impaired child?
The affected child, their parents, teacher, social worker, rehabilitation specialist, pediatrician or ophthalmologist will often offer different but equally valid answers to this question. The issue is not which is “correct” but which definition to choose for epidemiological research, for assessing/planning services and in clinical practice.
A standardized definition is necessary in order to compare reliably the frequency, causes, treatment, or prevention of VI within and between countries and over time. The World Health Organization (WHO) classification of visual impairment (Table 1.1)3 is now based on the “presenting” acuity in the better-seeing eye (i.e. at the level of the person not the eye) measured with optical correction, if usually worn, rather than the best corrected acuity used previously. Thus,
TABLE 1.1 World Health Organization classification of visual impairment3
Presenting
Category
0 No vision impairment
1 Mild vision impairment 6/12 (LogMAR 0.3) 6/18 (LogMAR 0.48) 5/10 (0.5) 3/10 (0.3) 20/40 20/70
2 Moderate vision impairment 6/18 (LogMAR 0.48) 6/60 (LogMAR 1.0) 3/10 (0.3) 1/10 (0.1) 20/70 20/200
3 Severe vision impairment 6/60 (LogMAR 1.0) 3/60 (LogMAR 1.3) 1/10 (0.1) 1/20 (0.05) 20/200 20/400
4 Blindness 3/60 (LogMAR 1.3) 1/60 (LogMAR 1.7) 1/20 (0.05) 1/50 (0.02) 20/400 No light perception 5/300 (20/1200) or CF at 1 meter
5 Blindness 1/60 (LogMAR 1.7) Light perception 1/50 (0.02) 5/300 (20/1200)
6 Blindness No light perception
9 Undetermined or unspecified
Category Presenting near visual acuity
Near vision impairment Worse than N6 or M0.8 with existing correction tested with both eyes open
CF, counting fingers; MAR, minimum angle of resolution. If the extent of the visual field is taken into account, patients with a visual field of the better eye no greater than 10° in radius around central fixation should be placed under “binocular” blindness. For monocular blindness, this degree of field loss would apply to the affected eye.
uncorrected refractive error, i.e., the individual does not already have optical correction, now falls within the definition. This recognizes the fact that access to optical correction is very limited in some populations, making uncorrected refractive error a significant cause of functional impairment. Since refractive error is common, this important change in classification must be taken into account when comparing both the overall prevalence reported and relative importance of different causes of VI in studies conducted using the prior classification. As such, the data presented in this chapter do not include children with visual impairment due to undiagnosed or uncorrected refractive error alone. This group possibly comprises over 12 million children, most living in Southeast Asia with uncorrected myopia (Box 1.3).
The WHO classification is used in epidemiological research, despite the difficulties of measuring visual acuity in very young children and those unable to cooperate with formal testing. Investigators map behavioral responses/qualitative methods (e.g. using the central,
BOX 1.3 Key gaps in current knowledge about epidemiology and the impact of visual impairment on children
For many regions of the world, there is currently very limited contemporary population-based information about frequency, burden, and etiology.
There is limited understanding of the following:
• long-term ophthalmic disease, general and mental health, educational, occupational, and social outcomes for affected children and the adults they become
• social, economic, and personal impact on the families of affected children
• economic consequences – including financial and other costs associated with medical treatment, rehabilitation, social support and care, as well as loss of productivity.
The opportunities and infrastructure for research to address these questions are better in industrialized countries, so there is currently a differential information gap.
following and maintaining (CSM) fixation notation) to broad categories of vision.4 Technological innovations for testing vision in young children are likely to emerge over time, such as eye tracking software.5 Nevertheless, there is a need in epidemiological research and also arguably in clinical practice for a better classification system applicable to children of different ages. This should consider other aspects of vision, such as binocularity and contrast sensitivity, as well as normal visual development. However, developing suitable methods for use in nonclinical research settings will be challenging.
Adoption of the WHO International Classification of Functioning, Disability and Health (ICF) reflects the new framework for understanding disability and the relationship between health conditions, personal, and societal factors.6 Also, the importance of measuring patientreported outcomes (PROs/PROMs) using self-rated/self-completed questionnaires, is now accepted within many healthcare systems, to help improve the quality of care. Two types of PROMs are particularly relevant to pediatric ophthalmology. Firstly, functional vision measures of child’s/young person’s own rating of their ability (difficulty or ease) for tasks of daily living dependent on vision, such as navigating independently.7,8 Secondly vision-related quality of life that elicits the child’s or young person’s view of the gap between his/her expectations and his/her actual experiences with respect to the physical, emotional/psychological, cognitive, and social impacts of the visual disorder and its therapy.9
Measures of frequency and burden of childhood visual impairment
The analogy of a barrel of white and red grapes with a hole in the bottom can be used to illustrate measures of frequency and the burden of disease. In this analogy, white grapes represent those without the condition of interest (“healthy”) and red grapes represent those who have the condition of interest (“diseased”). The total number of grapes (white plus red) in the barrel represents the population of interest (e.g. all children aged 0–15 years). The proportion of all the grapes in the barrel that are red at any given time denotes prevalence. The total number of red grapes in the barrel at any given time reflects the magnitude or burden of the disease in the population. The speed at which red grapes enter the barrel equates with incidence, i.e. the rate of new occurrence of disease in a given population over a specified time. For example, in the UK the annual incidence of congenital cataract was estimated to be 2.5 per 10,000 children aged ≤1 year in 1995.10
However, the proportion in a population that is diseased (i.e. the prevalence) is dynamic, as some grapes (both red and white) leave the barrel through the hole in the bottom. The “diseased” (i.e. red grapes) can leave through mortality, which may be higher amongst those diseased, or by out-migration, or as a result of treatment that means they are no longer classified as diseased. At the same time, more red and white grapes are being added to the barrel. The prevalence (proportion of grapes that are red) at any given time is, therefore, a balance between how fast red (and white) grapes are added and how quickly they leave the barrel. For example, the current UK prevalence in children of amblyopia with an acuity of worse than logMAR 0.3 (6/12, 20/40, 0.5) is about 1%.11
Prevalence and incidence data provide complementary information. Incidence identifies and monitors trends over time that reflect changing exposure to risk factors, or the emergence of new exposures or the introduction of effective public health measures for control (such as rubella immunization and childhood cataract). Incidence data are useful for planning the provision of services and research, e.g. estimating likely recruitment time in clinical trials. Prevalence indicates the proportion of the population with the condition at a given time. It helps allocate resources and can be used to evaluate services, if changes in prevalence can be attributed solely to changes in outcome or duration of disease as a result of treatment rather than changes in underlying incidence.
Measures of disease frequency do not, however, give any indication of the health economic impact (or “burden”) nor the consequences of the disease. These aspects are very important in order to determine priorities and allocate resources, providing a metric at population level that complements PROs assessed at an individual level. Measures of “utility” such as disability-adjusted life years (DALYs) or quality-adjusted life years (QALYs) are often used for this purpose in research with adults, as they incorporate morbidity or mortality into a single measure that can be used to compare different states of health within and between countries. Disability weights, which range from 0 (perfect health) to 1.0 (death), are used to calculate DALYs. These were revised in 2015; the weight for moderate vision impairment is unchanged at 0.034, but the weight for blindness was reduced from 0.6 to 0.17.12,13 There are concerns that the lower weight and hence lower DALYs for blindness, including among children, may have negative consequences for advocacy, benchmarking, and resource allocation.14 The direct applicability of these measures to children and young people is not fully established. As such, and also because large-scale population-based epidemiological studies of childhood visual impairment remain scarce, health economics research in the area of childhood VI remains limited.
POTENTIAL SOURCES OF INFORMATION ABOUT VISUAL IMPAIRMENT
There are a number of sources of epidemiological information about childhood VI or blindness but, in reality, only a few are available in most countries. This explains the currently incomplete picture (see Box 1.3).15
• Population-based prevalence studies: These represent a source of precise, representative estimates of burden (frequency) and causes. However, the few studies of whole populations of children with VI, such as prior and upcoming national birth cohort studies in the UK,16 need to be very large (a study of 100,000 children is required in an industrialized country to identify 100–200 children with VI or blindness): these are costly and difficult to do.
• Population-based incidence studies: Studies of all-cause incident (newly occurring) VI are even more difficult, explaining their rarity.17, 18
• Special needs/disability registers and surveillance: Specific studies and/ or surveillance systems19 or registers of childhood disability20 can provide information about VI, but it is important to recognize the potential for bias, as certain visually impaired children may be overrepresented in these sources, e.g. those with multiple impairment.
• Studies of intervention/service-based populations: In developing countries, studies of children in special education provide information on causes, but these may be biased because many affected children (particularly those with additional non-ophthalmic impairments) do not have equal access to special education. With other service-based studies, e.g. from clinic attendees, the interpretation of findings and their extrapolation to other populations needs to take these biases into account, as children with treatable conditions are likely to be over-represented.
• Visual impairment registers: These exist in many industrialized countries but, if registration is voluntary and not essential for accessing special educational or social services, registers may be incomplete as well as biased, as they will reflect differences in parental preferences and professionals’ practices regarding registration of eligible children.21,22
• Visual impairment teams: Increasingly, children in industrialized countries are evaluated by multidisciplinary teams. They can provide useful information if these teams serve geographically defined populations.
• Disorder-specific ophthalmic surveillance schemes: Uncommon eye conditions in children can be studied using population-based surveillance schemes, and have enabled studies, for example, of congenital eye anomalies, congenital glaucoma and adverse drug reactions.23–25 Under-ascertainment can occur. In the United Kingdom, the national active surveillance scheme includes all senior ophthalmologists (the British Ophthalmological Surveillance Unit).19 This unit facilitates studies of uncommon disorders, including the first population-based incidence study of SVI and blindness in childhood17 and subsequently the first study of VI, SVI, and blindness.18 This is an important resource for pediatric ophthalmic epidemiological research in the UK and a potential model for other settings.
• Community-based rehabilitation programs: In many developing countries, rehabilitation of blind and VI children occurs within the community. If the size of the catchment population is known, it is possible to estimate prevalence and obtain population-based data on causes.26
• Case ascertainment using key informants: In many developing countries, it may be possible to identify key community and religious leaders, healthcare workers, and others who know their communities well and thus can identify children believed to have VI or ocular disorders. This can be combined with the size of the population at risk, to estimate prevalence and provide population-based data on the causes.26,27
• Household surveys are commonly used in many low-income countries to collect data on a range of health indices. This approach can also be used to identify children who are blind.28
• Data modeling can also be used for specific conditions, as has been used to estimate the global incidence of blindness and visual impairment from retinopathy of prematurity.29
Regardless of the sources, ascertainment is often incomplete and/or biased. For example, in industrialized countries, families from socially disadvantaged groups or ethnic minorities are less likely to participate in research on health services for visually impaired children.20 Participation/ selection bias affects our ability to generalize findings, especially in research on rare disorders. Also, in some communities in low-income
countries, having a disabled child is a source of stigma, which can lead to under-ascertainment in community-based key informant or household surveys. Using multiple sources generally provides a more complete and reliable picture of causes and frequency of childhood VI.30–32
IMPACT OF VISUAL IMPAIRMENT
Visual impairment in childhood impacts on all aspects of the child’s development33,34 and shapes the adult he/she becomes, influencing health, well-being and education,35 particularly in low-income countries,36 and employment,37 social prospects, and lifelong opportunities. Visual impairment also impacts the families of affected children, both in terms of their own general health, mental health and well-being, and on their resources.38–40 Although the prevalence and incidence of VI are lower in children than in adults, the years of life lived with VI (“person-years of visual impairment”) are considerable.41 Personal and social costs are important, but difficult to measure (see Box 1.3). The economic costs of childhood VI in terms of loss of economic productivity are significant,42 a quarter of the costs of adult blindness in some countries.43 For example, in India an estimated annual cumulative loss of gross national product attributable to childhood VI was US$22 billion.43
VISUAL IMPAIRMENT IN THE BROADER CONTEXT OF CHILD HEALTH AND CHILDHOOD DISABILITY
Multiple impairments
In high-income countries, at least half of all severely visually impaired and blind children also have significant motor, sensory, or learning impairments or chronic systemic disorders which impact development, education, and independence.17,44 In low-income countries, the proportion is probably smaller, reflecting the higher incidence of conditions such as ophthalmia neonatorum, which causes purely ocular disease, and the high mortality rates among children who are blind from conditions associated with multiple impairment, for example congenital rubella syndrome, meningitis, cerebral palsy or brain tumors.
For research on etiology and interventions, and for provision of services, it may be helpful to think about two separate populations:
• children with isolated VI;
• children with VI and other impairments or systemic diseases.
Mortality
Children with visual impairment are more likely to die during childhood than the general population of children. In low-income countries,45,46 children who become blind from keratomalacia (acute vitamin A deficiency) have a very high mortality rate. Other blinding conditions are also associated with high mortality, e.g. measles infection, meningitis, congenital rubella syndrome. But even in high-income countries, visually impaired children have higher mortality rates: in the UK, 10% of SVI or blind children died within a year of diagnosis in one study,17 and 4% in a study of VI, SVI or blind children.18
Prevalence studies of older visually impaired children exclude those who died before school age. This underestimates the true frequency and results in bias when studying only surviving children.
Groups at high risk of visual impairment
In research and resource allocation, VI should be viewed in the context of other childhood disabilities. There is increasing recognition of the
importance of social determinants (sex, ethnicity, socio-economic status and cultural factors) of visual health47,48 which are poorly defined, but some children are at increased risk of visual loss: children with low birth weight, those who are socioeconomically deprived or from ethnic minorities.17,49 In some settings, particularly in Asia, girls may also have less access to services than boys, and remain blind.18,50 Because these higher-risk groups are also less likely to participate in health services research,51 selection bias may occur through sociodemographic factors.
SUMMARY OF GLOBAL FREQUENCY AND CAUSES OF CHILDHOOD VISUAL IMPAIRMENT
Prevalence estimates
In the absence of direct data for many settings, an approach has been developed to estimate a proxy prevalence based on the association between the prevalence of blindness in children and the under-5 mortality rates (U5MRs) for a country.45,52 In high-income countries with U5MRs of less than 20 per 1000 live births, the prevalence of blindness is approximately 3–4 per 10,000 children. By contrast, in countries with U5MRs of >200 per 1000 live births (e.g. the poorest countries in sub-Saharan Africa), the prevalence of blindness is nearer 12–15 per 10,000 children. This reflects three factors:
• exposure to risk factors and potentially blinding conditions that do not occur in affluent regions (e.g. vitamin A deficiency, cerebral malaria);
• the occurrence of conditions adequately controlled elsewhere (e.g. measles infection and congenital rubella through immunization);
• limited access to services and treatments that ameliorate disease progression (e.g. screening and treatment of retinopathy of prematurity [ROP])38 or that restore visual function (e.g. high-quality management of cataract).
Prevalence of VI in children
Incidence and prevalence studies reported since 2000 have used a range of different methodologies, age groups, and definitions, resulting in widely differing estimates (Table 1.2).
There is a trend of higher prevalence of VI in low-income countries, such as Sudan, Bangladesh, and India than in high-income countries, which increases as under-5 mortality rates (U5MR) increase. However, the lower than expected prevalence estimates for sub-Saharan African countries, where U5MRs are high, are probably artefacts, arising from methodological or cultural issues when the key informant method has been used for case ascertainment. Another explanation is that blind children in Africa have a very high mortality rate. The prevalence of VI is still not known for many regions (see Table 1.2).
In most settings, SVI and blindness (BL) account for one-third of all levels of visual impairment. In high-income countries, the combined prevalence of VI, SVI, and BL is about 10–22 per 10,000 children aged <16 years, while in some low-income countries it is 30–40 per 10,000.46
Magnitude of blindness in children
Due to lack of population-based data from many countries, estimates of the number of blind/SVI children have been derived using U5MRs as a proxy indicator.52 In 1999 when VISION 2020 was launched, it was estimated there were 1.4 million blind children aged 0–15 years in the world,45 derived using U5MRs for 1994, to reflect the midpoint of the
TABLE 1.2 Incidence and prevalence of severe visual impairment and blindness in children aged 0–15 years published between 2000 and 2020, by Global Burden of Disease super region
GBD super region/ Reference
Incidence data
High Income: Asia Pacific, North America, Australasia, Western Europe
Rahi 200317 UK
Teoh 202018 UK
6/60
(5.3–6.5)/10,000 by age 16
10,000 by age 1 year
(9.4–10.8)/10,000 by age 18 years
Pandova 201983 Kuwait Register 0–20 <6/60; VF 11/100,000 person years
Prevalence data
High Income: Asia Pacific, North America, Australasia, Western Europe
Flanagan 200384 Scotland Multiple sources <19
Mezer 201585 Israel Register 0–3
Central Europe, Eastern Europe, Central Asia
Bulgan 200286 Mongolia Mixed methods <16
Southeast Asia, East Asia, Oceania
Xiao 201187 China SE KIM
Lu 200988 China
Fu P 200489
TABLE 1.2 Incidence and prevalence of severe visual impairment and blindness in children aged 0–15 years published between 2000 and 2020, by Global Burden of Disease super region
GBD super region/ Reference Country
Muhit 201890 Indonesia Mixed methods <16
Razavi 201027 Iran KIM <15
Cama 201030 Fiji Mixed methods <16
Limburg 201231 Vietnam RAAB/KIM <16
Latin America, Caribbean – no data
North Africa, Middle East
Shahriari 200791 Iran PB survey 10–19
South Asia
Muhit 201028 Bangladesh Household survey <16
6/60 0.24/1000 (no CI reported)
6/60 0.4 (0.3–0.5)/1000
3/60 0.76 (4.9–11.8)/1000
6/60 0.8 (0.58–1.06/1000)
Murthy 201492 Bangladesh KIM <18 <6/60 0.7 (0.6–0.8)
Husain 201993 Bangladesh House to house survey <16 <3/60 0.63 (0.4–0.9)
Dorairaj 200894 India S Household survey <16 <3/60 (0.50–1.6)/1000
Nirmalan 200395 India S PB survey <16 <6/60 0.62 (1.5–11.0)
Parkar 200796 India C KIM 0–15 <6/60 0.6 (0.4–0.8)/1000
Adhikari 201497 Nepal Household survey 0–10 <6/60 0.7 (95% CI 0.2–1.2)/1000
Byanju 201998 Nepal KIM/school teachers <16 <6/60 0.3 (0.29–0.31)/1000
Sub-Saharan Africa
Nallassamy 201199 Botswana Radio/outreach <16 <6/18 0.23/1000
Demisse 2011100 Ethiopia KIM <16 <6/60 0.62 (0.42–0.82)/1000
Kalua 2012101 Malawi S KIM/HSAs <16 <3/60 0.11/1000
Duke 2013102 Nigeria SE KIM ND <6/60 0.09–0.22/1000
Aghaji 2017103 Nigeria SE KIM <16 <6/60 0.12 (0.07–0.19)
Zeidan 2007104 Sudan (Khartoum) Household survey <16 <6/60 1.4 (1.0–1.8)/1000
Shirima 2009105 Tanzania KIM <16s <3/60 0.17/1000
CI, confidence interval; HSAs, Health Surveillance Assistants; KIM, key informant method; ND, no data; PB, population-based; RAABS, Rapid Assessment of Avoidable Blindness Survey; VF, visual fields; VI, visual impairment. Note: References 83–105 are available online.
16 years of childhood, and the child population of each country for 1999. The figures were revised in 2010 and, because of falling U5MRs and a relatively stable child population, the estimate had fallen by 10% to 1.26 million,53 and had fallen again to 1.14 million by 2015. The revised estimate for 2020, 1.024 million, used the GBD seven super regions for the first time (Fig. 1.1 and Table 1.3).54 These regions comprise 21 smaller regions grouped by their geographical closeness and epidemiological similarity, which is largely driven by the social determinates of health (genetics, behavior, environmental and physical influences, medical care, and social factors).55 An advantage of using GBD regions is that data of relevance to VI in children, e.g., preterm birth rates, also are reported using these regions. Sub-Saharan Africa and South Asia (approximately 350,000 and 300,000, respectively) have the highest number of blind children, and Central Europe/Eastern Europe/Central Asia and Latin America/Caribbean have the lowest (approximately 30,000 and 50,000, respectively). Comparing the number of blind children per 10 million total population reveals a 5.5-fold difference between the High Income super region (57/10 million population) and
Sub-Saharan Africa (313/10 million), reflecting regional demographic and blindness prevalence estimate differences.
Incidence
Contemporary incidence data are lacking for many countries. Since 2000, only two incidence studies have been reported (see Box 1.3 and Table 1.2).
In the UK, a national population-based study of severe vision impairment (SVI) and blindness (BL) conducted in 2000 showed that the age groupspecific incidence was highest in the first year of life at 4.0 per 10,000 per year, with the cumulative incidence (lifetime risk) increasing to 5.9 per 10,000 by 16 years of age.17 A second UK study, a national populationbased study of the full spectrum of visual disability, encompassing vision impairment (VI), severe vision impairment, and blindness (VI/SVI/B), reported an annual incidence of 5.2 per 10,000 in the first year of life, with a cumulative incidence by 18 years of 10.0 per 10,000 in the UK in 2015/16.18 These estimates are likely to be applicable to countries with similar socioeconomic development and access to services, but the incidence in many lower-income countries is probably higher.
