Background. India's National Programme for Control of blindness focuses almost exclusively on cataract, based on a national survey done in the 1980s which reported that cataract caused 80% of the blindness in India. No current population-based data on the causes of blindness in India are available. We assessed the rate and causes of blindness in an urban population in southern India. Methods. We selected 2954 participants by stratified, random, cluster, systematic sampling from Hyderabad city. Eligible participants were interviewed and given a detailed ocular assessment, including visual acuity, refraction, slitlamp biomicroscopy, applanation intraocular pressure, gonioscopy, dilatation, grading of cataract, stereoscopic fundus assessment, and automated-threshold visual fields. Findings. 2522 participants, including 1399 aged 30 years or more, were assessed. 49 participants (all aged ≤ 30 years) were blind (presenting distance visual acuity < 6/60 or central visual field < 20°in the better eye). The rate of blindness among those aged 30 years or more, adjusted for age and sex, was 3.08% ([95% CI 1.95-4.21]). Causes included cataract (29.7%), retinal disease (17.1%), corneal disease (15.4%), refractive error (12.5%), glaucoma (12.1%), and optic atrophy (11.0%). 15.7% of the blindness caused by visual-field constriction would have been missed without visual-field examination. Also without visual-field and detailed dilated-fundus assessments, blindness attributed to cataract would have been overestimated by up to 75.8%. If the use of cataract surgery in this urban population was half that found in this study, which simulates the situation in rural India, cataract would have caused 51.8% (39.4-64.2) of blindness, significantly less than the 80% accepted by current policy. Interpretation. Much of the blindness in this Indian population was due to non-cataract causes. The previous national survey did not include detailed dilated-fundus assessment and visual-field examination which could have led to overestimation of cataract as a cause of blindness in India. Policy-makers in India should encourage well-designed population-based epidemiological studies from which to develop a comprehensive long-term policy on blindness in addition to dealing with cataract.
Bibliographical noteFunding Information:
This study was supported by the Hyderabad Eye Research Foundation, Hyderabad, India. We thank Hugh R Taylor, University of Melbourne, Melbourne, Australia, and K Vijayaraghavan, National Institute of Nutrition, Hyderabad, India, for guidance in study design; Pyda Giridhar, V Nagaraja Naidu, M N K E Prasad, Kovai Vilas, and M Moinuddin for the mapping of selected blocks and recruitment of participants; Soma Mandal for help with assessment of participants; V Malathi, B Srinivas, and K Madhu Chander for help with data management; the staff of Information Systems Department, L V Prasad Eye Institute, Hyderabad, India, for the programming of databases; and the participants for taking part in the study.