Blindness in Childhood
Since VISION 2020 was launched in 1999, controlling blindness in children has been a high priority.
In 1997 WHO held a meeting, during which the estimate of numbers of blind children was revised to 1.4 million: a new method was used to estimate the magnitude for countries where these data were not available, which was based on the association between under-five mortality rates and the prevalence of blindness in children. This method is still being used, as data from more recent population-based surveys confirm that the prevalence of blindness in children and under-five mortality rates correlate reasonably well. Under-five mortality rates are also being used as a proxy indicator of vitamin A deficiency in children.2
In 1997, it was estimated that 45% of blind children were blind from avoidable causes and that the pattern of causes varied widely between and even within countries.4 The following conditions were prioritised for control: corneal scarring (mainly from Vitamin A deficiency and measles), cataract, retinopathy of prematurity, refractive error (mostly myopia), and low vision.3
Vitamin A deficiency and measles
Vitamin A deficiency (VAD) remains a significant a cause of preventable childhood blindness and increased risk of mortality among children under five years of age... (See Vit A page)
Measles immunisation is another large-scale public health intervention to reduce child morbidity and mortality. Since the launch of EPI in 1974, coverage with measles immunisation has increased to target levels in most regions. Measles epidemics are now relatively rare and measles-related corneal blindness has also declined. As with vitamin A deficiency, there are still communities of children at risk, particularly in sub-saharan Africa, where the majority of measles cases and measles-related deaths now occur.
Cataract in children
Because corneal blindness is declining in many countries in Africa and Asia, cataract is becoming a relatively more important cause of avoidable blindness. The management of cataract in young children has changed dramatically over the last 20 years. When intraocular lenses (IOLs) were first used in the late 1970s, they were thought not to be suitable for children. Over the last decade, smaller, high-power IOLs, suitable for children, have become available; surgical techniques and equipment have also evolved. Many paediatric ophthalmologists now insert IOLs in children as young as 12 months of age. However, this technique requires considerable expertise and a vitrectomy machine, as the posterior capsule and anterior vitreous have to be removed in young children. Long-term follow-up is also crucial to manage visual axis opacities and to ensure the child is given optimal optical correction and low vision devices, if required.
Retinopathy of prematurity (ROP)
Refractive error in children
Little was known about the magnitude of vision loss due to refractive error in children until the late 1990s. Since 2000, WHO has worked with the National Eye Institute, USA, to undertake standard, population-based surveys of the prevalence of refractive error in all regions of the world among children aged five or seven up to 15 years. The findings show that refractive errors are more prevalent in children in Asian countries than in other regions, and that myopia, which increases with increasing age, is the commonest refractive error in older children. Myopia is also more common in children from urban areas than in those from rural areas. The current thinking is that myopia is caused by the influence of genes as well as environmental factors, and that outdoor activity may protect children from myopia. We also know from studies in Tanzania9 and Mexico, that a high proportion of children with refractive error identified in school eye health programmes do not wear the spectacles provided. All these studies provide important information for those planning school screening for refractive error.
Functional low vision in children
Recent data from the studies of refractive error mentioned above suggest that the prevalence of functional low vision (corrected visual acuity in the better eye ranging from <6/18 to, and including, light perception from untreatable causes) is approximately twice the prevalence of blindness: there are almost 3 million children worldwide who have the potential to benefit from low vision care.10It is, therefore, essential that low vision services be part of eye care services for children at all levels of service delivery.
The control of blindness in children is a VISION 2020 priority because the number of ‘blind person years’ resulting from blindness starting in childhood is second only to cataract. If VISION 2020 targets for children can be met, the global prevalence of blindness will have fallen from 7.5/10,000 children (in 1997) to 4/10,000 children by the year 2020. The number of children who are blind will decline to approximately 800,000.
Extracted with permission from an Article by Professor Clare Gilbert and Dr Mohammed Muhit in Community Eye Health Journal Vol. 21 No. 67 2008 pp 46 - 47. Published online 01 September 2008. http://www.cehjournal.org
- World Health Organization. Report of the WHO Meeting on the Prevention of Childhood Blindness. WHO/PBL/90.19. WHO, Geneva, 1990.
- Sommer A et al. Assessment and control of vitamin A deficiency: The Annecy Accords. J Nutr 2002;132: 2845S–2850S.
- Gilbert C et al. Childhood blindness: a new form for recording causes of visual loss in children. Bull World Health Organ 1993;71: 485–489.
- Gogate P et al. Blindness in children: a wordwide perspective. Comm Eye Health J 2007;20(62); 32–33.
- World Health Organization. Preventing blindness in children. WHO/PBL/00.77. WHO, Geneva, 1999.
- Muhit M. Finding children who are blind. Comm Eye Health J 2007;20(62); 30–31.
- Waddell K. Childhood blindness and low vision in Uganda. Eye 1998;12: 184–192
- Gilbert C. Retinopathy of prematurity: a global perspective of the epidemics, population of babies at risk and implications for control. Early Hum Dev 2008;84: 77–82.
- Wedner SH et al. Two strategies for correcting refractive errors in school students in Tanzania: randomised comparison, with implications for screening programmes. Brit J Ophthalmol 2008;92: 19–24.
- Gilbert CE et al. The prevalence and causes of functional low vision in school-age children: results from standardized population surveys conducted in Asia, Africa and Latin America. Invest Oph Vis Sci 2008;49: 877–881.
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