Objective: To determine the prevalence of blindness and vision impairment in a rural population of southern India.
Design: A population-based cross-sectional study.
Participants: A total of 17200 subjects aged 6 years or older, including 5150 subjects aged 40 years or older from 50 clusters representative of three southern districts of Tamil Nadu in southern India.
Methods: All participants had preliminary screenings consisting of vision using a LogMAR illiterate E chart and anterior segment hand light examinations at the village level. Subjects aged 40 years or older were offered comprehensive eye examinations at the base hospital, including visual acuity using LogMAR illiterate E charts and refraction, slit-lamp biomicroscopy, gonioscopy, applanation tonometry, dilated fundus examinations, and automated Humphrey central 24-2 full threshold perimetry; subjects younger than 40 years of age who had any signs or symptoms of ocular disease were also offered comparable examinations at the base hospital.
Main outcome measures: Visual impairment was defined as best-corrected visual acuity <6/18, and blindness was defined using both Indian (<6/60) and World Health Organization (<3/60) definitions.
Results: Comprehensive examinations at the base hospital were performed on 5150 (96.5%) of 5337 persons 40 years of age or older. Among those 40 years of age and older, presenting visual acuity at the <3/60 level was present in 4.3% (95% confidence interval [CI]: 3.8, 4.9) and 11.4% (95% CI: 10.6, 12.3) at the <6/60 level. After best correction, the corresponding figures were 1.0% (95% CI: 0.79, 1.2) and 2.1% (95% CI: 1.7, 2.5). Over 70% of subjects improved their vision by at least one line, and nearly a third by three lines after refraction. Age-related cataract was the most common potentially reversible blinding disorder (72.0%) among eyes presenting with blindness.
Conclusions: Blindness and vision impairment remain major public health problems in India that need to be addressed. Cataracts and refractive errors remain the major reversible causes for the burden of vision impairment in this rural population.