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Prevalence and causes of visual impairment in a Brazilian population: The Botucatu Eye Study

DOI: 10.1186/1471-2415-9-8

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A population-based cross-sectional study was conducted involving a random start point and then systematic sampling of an urban Brazilian population in the city of Botucatu. There were approximately 3 300 individuals aged 1 to 91 years who were eligible to participate in the study. Of this sample, 2485 (75.3%) underwent ophthalmic examination. The ophthalmic examination included uncorrected (presenting) and best corrected distance visual acuity using standardized protocols. The primary cause of decreased visual acuity was identified for all patients with visual impairment.Presenting low vision and presenting blindness were found in 5.2% (95% CI: 4.3–6.1) and 2.2% (95% CI: 1.6–2.8) of the population, respectively. Unilateral presenting low vision and unilateral presenting blindness were found in 8.3% (95% CI: 7.2–9.5) and 3.7% (95% CI: 2.9–4.4) of the population respectively. Best corrected low vision was found in 1.3% of the population (95% CI: 0.9–1.7) and best corrected blindness was discovered in 0.4% of people (95% CI: 0.2–0.7). The main cause of presenting low vision was refractive error (72.3%) and cataract was the most prevalent cause of blindness (50%).The main causes of low vision and blindness in this Brazilian city were uncorrected refractive errors, cataract, and retinal diseases. Programs to further reduce the burden of visual impairment need to be targeted toward the correction of refractive error and surgery for cataracts.In 2002, the World Health Organization (WHO) estimated that there were in excess of 161 million people worldwide with visual impairment (corrected VA < 6/18 in the better eye), including 37 million with blindness (corrected VA < 3/60 in the better eye) [1,2]. If this definition is expanded to include uncorrected refractive error then it is estimated that 259 million people are visually impaired [3]. The burden of blindness is particularly severe in South-East Asia and India; however in countries such as Brazil, the prevalence of blind


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