The Bangladesh National Blindness and Low Vision Survey - Identification of prevalence, causes and the need for eye care services
Dineen, Brendan Patrick
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Background: Bangladesh is a densely populated, impoverished country in South Asia with inadequate health service provision for a variety of diseases including treatable ocular conditions. The aims of this comprehensive research study were: a) to determine the prevalence and causes of blindness and low vision amongst persons aged 30 years and older, based on a nationally representative, randomly selected sample, b) to evaluate cataract surgical coverage and spectacle coverage for refractive errors, and c) to identify the socio-economic and cultural barriers to the uptake of eye care service provision amongst blind and visually impaired individuals. Methods: Multi-stage, cluster random sampling with probability-proportional-to-size procedures were used to select the sample of 12,782 adults age 30 years and older. Cluster site selection for the study was proportional to the rural/urban distribution of the national population. The examination protocol consisted of an interview, visual acuity (VA) testing, automated refractometry and optic disc examination on all subjects. Corrected VA re-testing, cataract grading, and a dilated fundal examination were performed on all visually impaired subjects. The definitions of blindness (<3/60) and low vision (<6/12 to ≥3/60) were based on the presenting visual acuity in the better eye. The World Health Organization/Prevention of Blindness proforma and its classification system for identifying the main cause of blindness and low vision for each visually impaired subject was used. Descriptive, univariate and multi-variable statistical analysis techniques, including binary logistic regression modelling, were carried out using Epi-Info and SPSS software. Results: In total, 11,624 adult subjects were examined (90.9% response rate) across the 154 cluster sites. An age-sex standardised prevalence of bilateral blindness of 1.53% was identified while a further 13.8% of subjects had low vision (<6/12 VA) binocularly. The main causes of low vision were cataract (74.2%), refractive error (18.7%), and macular degeneration (1.9%). Cataract was the predominant cause (79.6%) of bilateral blindness followed by uncorrected aphakia (6.2%) and macular degeneration (3.1%). Cataract surgical coverage (CSC) in eyes blind due to cataract was inadequate (31.8%), with older persons, females, those from rural areas and illiterate persons having the lowest CSC levels. Spectacle coverage for those with refractive errors (myopia or hypermetropia) was likewise low (19.9%). The main barrier to cataract surgery was ‘poverty’, as reported by those with visually-impairing cataract. Conclusions: By extrapolation to the national population of Bangladesh, there were an estimated 650,000 blind adults (95% CI: 552,175 - 740,736) aged 30 years and older, the large majority of whom were suffering from operable cataract. A further 21 million adults were visually impaired due to refractive errors. This research study emphasised the importance of further development and implementation of the national eye care services plan in order to increase the accessibility, the affordability and the uptake of essential eye care service delivery, especially amongst the most vulnerable groups in the country.
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