Prevalence of cataract in an older population in India: the India study of age-related eye disease.

PURPOSE: To describe the prevalence of cataract in older people in 2 areas of north and south India. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: Randomly sampled villages were enumerated to identify people aged ≥ 60 years. Of 7518 enumerated people, 78% participated in a hospital-based ophthalmic examination. METHODS: The examination included visual acuity measurement, dilatation, and anterior and posterior segment examination. Digital images of the lens were taken and graded by type and severity of opacity using the Lens Opacity Classification System III (LOCS III). MAIN OUTCOME MEASURES: Age- and gender-standardized prevalence of cataract and 95% confidence intervals (CIs). We defined type of cataract based on the LOCS III grade in the worse eye of: ≥ 4 for nuclear cataract, ≥ 3 for cortical cataract, and ≥ 2 for posterior subcapsular cataract (PSC). Any unoperated cataract was based on these criteria or ungradable dense opacities. Any cataract was defined as any unoperated or operated cataract. RESULTS: The prevalence of unoperated cataract in people aged ≥ 60 was 58% in north India (95% CI, 56-60) and 53% (95% CI, 51-55) in south India (P = 0.01). Nuclear cataract was the most common type: 48% (95% CI, 46-50) in north India and 38% (95% CI, 37-40) in south India (P<0.0001); corresponding figures for PSC were 21% (95% CI, 20-23) and 17% (95% CI, 16-19; P = 0.003), respectively, and for cortical cataract 7.6% (95% CI, 7-9) and 10.2% (95% CI, 9-11; P<0.004). Bilateral aphakia/pseudophakia was slightly higher in the south (15.5%) than in the north (13.2%; P<0.03). The prevalence of any cataracts was similar in north (73.8%) and south India (71.8%). The prevalence of unoperated cataract increased with age and was higher in women than men (odds ratio [OR], 1.8). Aphakia/pseudophakia was also more common in women, either unilateral (OR, 1.2; P<0.02) or bilateral (OR, 1.3; P