By Joanna Lyford, Senior medwireNews Reporter
The causes and prevalence of blindness in children vary markedly by geography, presumably as a proxy for socioeconomic factors influencing prevention and treatment schemes, conclude the authors of a literature review.
Paul Steinkuller (Baylor College of Medicine, Houston, Texas, USA) and colleagues conducted a systematic search of world literature on pediatric blindness published between 1999 and 2012.
They identified 41 relevant papers representing 33 countries; 26 of the studies were conducted in schools for the blind, six were population-based, six were hospital-based medical record reviews, and three were key informant studies.
The team also contacted all schools for the blind in the USA for information on causes of vision loss among pupils.
The available data suggest that in economically developed countries and regions, such as the USA, Canada, Western Europe, and Japan, the rate of childhood blindness is 0.3-0.4 per 1000 children, report Steinkuller et al in the Journal of the American Association for Pediatric Ophthalmology and Strabismus.
The prevalence of childhood blindness is intermediate in the Western Pacific region, at 0.2-0.7 per 1000, and in Asia, at 0.9 per 1000. In undeveloped countries the prevalence is as high as 1.2 per 1000, they state.
"Economic factors play a major factor role in rates of childhood blindness," the authors write. "Nine countries from the Africa region are represented, of which eight (89%) are low-income countries, where corneal disease was found to be the most frequent anatomic cause of visual impairment. In medium- and high-income countries, the retina is the major site of visual impairment."
The team estimates that in developing countries, an average of 51% of childhood blindness is avoidable, 27% is treatable, and 19% is preventable. Among avoidable and treatable causes, retinopathy of prematurity (ROP) is an emerging etiology.
Meanwhile, hereditary factors such as albinism, congenital cataracts with family history, and retinitis pigmentosa, predominate in the Americas, Europe, Asia, and Western Pacific
Regions, accounting for 23-44% of cases. In Sudan and other African countries, up to 40% of childhood blindness is caused by vitamin A deficiency.
Further insights came from analysis of data provided by 16 blind schools in the USA. Here, the leading causes of blindness were cortical visual impairment (18%), optic nerve hypoplasia (15%), and ROP (14%).
Less common causes, each accounting for 2-7% of the total, were optic atrophy, albinism, coloboma, glaucoma, non-ROP retinal detachment, Leber's congenital amaurosis, retinitis pigmentosa, microphthalmia/anophthalmia, cataract, and nystagmus.
"More detailed and accurate data from schools for the blind in the United States could be obtained by a unified survey using the standardized World Health Organization/Prevention of Blindness format or by creation of a national registry for blindness," the team remarks.
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