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An Update on Progress and the Changing Epidemiology of Causes of Childhood Blindness Worldwide

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An Update on Progress and the Changing Epidemiology of Causes of Childhood Blindness Worldwide Major Articles An update on progress and the changing epidemiology of causes of childhood blindness worldwide Lingkun Kong, MD, PhD,a Melinda Fry, MPH,b Mohannad Al-Samarraie, MD,a Clare Gilbert, MD, FRCOphth,c and Paul G. Steinkuller, MDa PURPOSE To summarize the available data on pediatric blinding disease worldwide and to present current information on childhood blindness in the United States. METHODS A systematic search of world literature published since 1999 was conducted. Data also were solicited from each state school for the blind in the United States. RESULTS In developing countries, 7% to 31% of childhood blindness and visual impairment is avoidable, 10% to 58% is treatable, and 3% to 28% is preventable. Corneal opacification is the leading cause of blindness in Africa, but the rate has decreased significantly from 56% in 1999 to 28% in 2012. There is no national registry of the blind in the United States, and most schools for the blind do not maintain data regarding the cause of blindness in their students. From those schools that do have such information, the top three causes are cortical visual impairment, optic nerve hypoplasia, and retinopathy of prematurity, which have not changed in past 10 years. CONCLUSIONS There are marked regional differences in the causes of blindness in children, apparently based on socioeconomic factors that limit prevention and treatment schemes. In the United States, the 3 leading causes of childhood blindness appear to be cortical visual impairment, optic nerve hypoplasia, and retinopathy of prematurity; a national registry of the blind would allow accumulation of more complete and reliable data for accurate determination of the prevalence of each. ( J AAPOS 2012;16:501-507) he definition and categorization of visual impair- worldwide: 39 million were blind, 246 million had low vi- ment was first made by the World Health Orga- sion, and 19 million were children (age 0-14).3,4 Of these, T nization (WHO) in 1972. A revision of this 12 million children (age 0-14) were visually impaired as definition was recommended by the International Classifica- the result of refractive errors, a condition that could be tion of Diseases in 2006.1 The 2010 WHO definition of easily diagnosed and treated, and 1.4 million were visual impairment (Table 1)2 comprises 4 levels of visual irreversibly blind.3 Approximately three-quarters of these function: normal vision (category 0), moderate visual impair- blind children live in developing countries, and up to ment (category 1), severe visual impairment (category 2), 60% of such children die within 1 year of becoming and blindness (categories 3-5). Moderate and severe blind.5 visual impairment are referred to as “low vision.” Low Although childhood blindness is relatively rare and com- vision taken together with blindness is referred to visual prises only 4% of total blindness, the impact is particularly impairment. tragic because children tend to live 40 years longer without According to the updated definition, it was estimated in vision than those with adult-onset vision loss6: the number 2010 that 285 million people were visually impaired of “blind years” experienced by children almost equals the total number of blind years caused by cataract in adults. These years are costly because the blind may have more Author affiliations: aDepartment of Ophthalmology, Baylor College of Medicine, Houston, difficulty securing gainful employment and because they Texas; bBaylor College of Medicine and UT School of Public Health; cThe International require resources from the health care system and their Center for Eye Health, Institute of Ophthalmology, University College, London, United Kingdom families. Childhood blindness also negatively affects neu- Submitted June 14, 2012. robehavioral development, which in turn affects the life Revision accepted September 3, 2012. quality of children and their families. Childhood blindness Correspondence: Paul G. Steinkuller, MD, Department of Ophthalmology, Baylor College of Medicine, 6701 Fannin St, Suite 640, Houston TX 77030 (email: pgsteink@ is a priority not only because interventions are available for texaschildrens.org). prevention but because of the number of blind years in- Copyright Ó 2012 by the American Association for Pediatric Ophthalmology and volved. In this study, we present up-to-date data on various Strabismus. 1091-8531/$36.00 causes of childhood blindness worldwide and in the United http://dx.doi.org/10.1016/j.jaapos.2012.09.004 States. Journal of AAPOS 501 Downloaded for Anonymous User (n/a) at The Curators of the University of Missouri from ClinicalKey.com by Elsevier on October 25, 2017. For personal use only. No other uses without permission. Copyright ©2017. Elsevier Inc. All rights reserved. 502 Kong et al Volume 16 Number 6 / December 2012 Table 1. Revision of categories of visual impairment (ICD-10), Organization/Prevention of Blindness (WHO/PBL) reporting Version for 2010 form, most had different criteria for admissions, and the ages of Best-corrected presenting distance the children varied from 0-15 to 1-18. We excluded children visual acuity .15 years of age according to date of birth. The number of stu- Level of visual Category impairment Worse than Equal to or better than dents in each school for the blind does not reflect the number of blind children in the United States. 0 Mild or none 6/18 3/10 (0.3) Data were analyzed by the same categorization for both world- 20/70 wide and U.S. data according to the anatomic site of the lesion 1 Moderate 6/18 6/60 causing the blindness and according to the stage of development 3/10 (0.3) 1/10 (0.1) at which the causative insult occurred. 20/70 20/200 2 Severe 6/60 3/60 1/10 (0.1) 1/20 (0.05) Results 20/200 20/400 3 Blindness 3/60 1/60a Data were collected from 41 publications representing 33 1/20 (0.05) 1/50 (0.02) countries. Twenty-six were blind school–based studies, 6 20/400 5/300 (20/1200) were population-based, 6 were hospital-based medical re- a 4 Blindness 1/60 Light perception cord reviews, and 3 were key informant studies. All studies 1/50 (0.02) reported using the standardized WHO vision classification 5/300 (20/1200) system; 17 (41%) used the WHO/PBL eye examination 5 Blindness No light perception 8 9 Undetermined or unspecified form (e-Supplement 1, available at jaapos.org). Of the 56 US schools for the blind visually impaired sur- ICD, International Classification of Diseases. aOr counting fingers at 1 meter. veyed, 6 had closed or moved and were unreachable. Sixteen schools (28.6%) from 15 states (Arizona, California, Flor- ida, Kansas, Kentucky, Louisiana, Maryland, Massachu- Methods setts, Minnesota, New Mexico, Oklahoma, Pennsylvania, A systematic search of world literature on childhood blindness South Carolina, Texas, and Washington) supplied data on published since 1999 was conducted. Ovid MEDLINE was a total of 3,070 students. Thirty-nine schools had no data searched for relevant publications from the period 1999-2012 or did not respond. using the following terms: blind, childhood blindness, visual impair- The available data suggest that in economically devel- ment, prevalence, and incidence. The search was limited to human oped countries and regions, such as the United States, studies in English. The list of countries for each World Bank de- Canada, Western Europe, and Japan, the rate of childhood velopment region (http://data.worldbank.org/country) was used blindness is 0.3 to 0.4 per 1,000 children. In the Western to find country-specific articles. Pacific region, the prevalence of childhood blindness is es- The United States does not have a national registry of the blind timated at 0.2 to 0.7 per 1,000; in Asia, 0.9 per 1,000 (range, 0.63-1.09). In undeveloped countries the prevalence can and visually impaired; however, surveys of schools for the blind in 5,9 other countries have become standardized and accepted means of reach 1.2 per 1,000. data collection within the past 20 years, and this methodology was used for US data in the present study. Schools for the blind in the Economic and Geographic Factors United States were contacted at least twice by telephone and sent Economic factors play a major factor role in rates of child- one letter to ascertain whether records were available regarding hood blindness. Of the 33 countries represented in our the causes of vision loss among their students. A total of 64 let- survey, 18 (55%) are classified by the World Bank as ters/data collection sheets were mailed to the 56 schools for the low-income countries, 10 (30%) as medium-income coun- blind from 50 states and Washington, DC, listed at http://www. tries, and 5 (15%) as high-income countries. Nine coun- medicalonline.com/disabled/schools/blindlist.htm. tries from the Africa region are represented, of which 8 On the basis of results from our 1999 study,7 a data collection (89%) are low-income countries, where corneal disease spreadsheet was developed and sent to all responding U.S. schools was found to be the most frequent anatomic cause of visual that had collected diagnosis data upon student enrollment. To en- impairment (28%). In medium- and high-income coun- roll in schools, children must be classified as visually impaired tries, the retina is the major site of visual impairment. when visual impairment (with correction) adversely affects In developing countries a mean of 51% (range, 31%- a child’s learning. This criterion generally includes both blind 70%) of childhood blindness is avoidable; 27% (range, and partially seeing children. We collected data on children con- 10%-58 %), treatable; and 19% (range, 3%-28%), prevent- sidered legally blind, defined as having (1) central visual acuity not able.
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