Date Published: July 3, 2007
Publisher: Public Library of Science
Author(s): Wanjiku Mathenge, John Nkurikiye, Hans Limburg, Hannah Kuper, Rupert Bourne
Abstract: BackgroundThe World Health Organization estimates that there were 37 million blind people in 2002 and that the prevalence of blindness was 9% among adults in Africa aged 50 years or older. Recent surveys indicate that this figure may be overestimated, while a survey from southern Sudan suggested that postconflict areas are particularly vulnerable to blindness. The aim of this study was to conduct a Rapid Assessment for Avoidable Blindness to estimate the magnitude and causes of visual impairment in people aged ≥ 50 y in the postconflict area of the Western Province of Rwanda, which includes one-quarter of the population of Rwanda.Methods and FindingsClusters of 50 people aged ≥ 50 y were selected through probability proportionate to size sampling. Households within clusters were selected through compact segment sampling. Visual acuity (VA) was measured with a tumbling “E” chart, and those with VA below 6/18 in either eye were examined by an ophthalmologist. The teams examined 2,206 people (response rate 98.0%). The unadjusted prevalence of bilateral blindness was 1.8% (95% confidence interval [CI] 1.2%–2.4%), 1.3% (0.8%–1.7%) for severe visual impairment, and 5.3% (4.2%–6.4%) for visual impairment. Most bilateral blindness (65%) was due to cataract. Overall, the vast majority of cases of blindness (80.0%), severe visual impairment (67.9%), and visual impairment (87.2%) were avoidable (i.e.. due to cataract, refractive error, aphakia, trachoma, or corneal scar). The cataract surgical coverage was moderate; 47% of people with bilateral cataract blindness (VA < 3/60) had undergone surgery. Of the 29 eyes that had undergone cataract surgery, nine (31%) had a best-corrected poor outcome (i.e., VA < 6/60). Extrapolating these estimates to Rwanda's Western Province, among the people aged 50 years or above 2,565 are expected to be blind, 1,824 to have severe visual impairment, and 8,055 to have visual impairment.ConclusionsThe prevalence of blindness and visual impairment in this postconflict area in the Western Province of Rwanda was far lower than expected. Most of the cases of blindness and visual impairment remain avoidable, however, suggesting that the implementation of an effective eye care service could reduce the prevalence further.
Partial Text: In 2004 the World Health Organization published the results of a major initiative to collate the available data on the prevalence of blindness . On the basis of data from surveys in 55 countries, the authors estimated that there were approximately 37 million blind people in the world. Recent surveys, however, have reported a lower than expected prevalence of blindness [2–4], which may reflect a real decline in blindness or may result from improvements in survey quality. In contrast, a recent survey carried out in a postconflict area in Southern Sudan reported a prevalence of blindness of 4.1%, more than four times as high as expected for Africa as a whole . There were methodological problems with this survey , but there are few other surveys available for postconflict areas to allow comparison. These data on the burden of blindness are needed to allow adequate planning and monitoring of eye care services. This is particularly true for low-income countries, where accurate data are needed to inform allocation of scarce resources.
The teams enumerated 2,250 people aged ≥ 50 y in the survey, of whom 2,206 (98.0%) underwent ophthalmic examination, 43 (1.9%) were not available, and one (0.04%) refused to be examined. The examined population was representative of the population of the province in terms of age and gender distribution (Table 1).
This survey of blindness in the Western Province of Rwanda found a far lower prevalence of blindness than expected based on current estimates for Africa . This may indicate that blindness is a less pressing public health concern for Rwanda than had previously been assumed. Despite the low prevalence, most of the cases of blindness and visual impairment were avoidable, suggesting that the prevalence can be reduced still further. The relatively low prevalence of cataract blindness may be partly attributable to the moderate cataract surgical coverage. The poor outcome after cataract surgery is of concern. Implementing a monitoring system for cataract surgical results could sensitise surgeons to quality control and help improve outcomes after surgery [11–14]. The provision of spectacles after surgery, improved follow-up after surgery and better selection of patients for surgery will also improve outcomes. The proportion of blindness and visual impairment due to posterior segment disease (including glaucoma and diabetic retinopathy) may grow as avoidable causes are brought under control, and with the continued global epidemic of diabetes, providing an important challenge in the future. The results for the Western Province may be generalisable to most areas in Rwanda (excluding Kigali and the central area) which are characterised by high levels of poverty and poor access to ophthalmic services.