Prevalence and causes of blindness in a rural south Indian population

Abstract: : Purpose: To study the prevalence and causes of bilateral blindness in a rural south Indian population. Methods: 3924 of 4800 enumerated (81.75 %) subjects, aged 40 years or more, from rural Tamil Nadu underwent a comprehensive ophthalmic examination including visual acuity testing, refraction, intraocular pressure, gonioscopy, dilated cataract grading (LOCS II), dilated retinal examination, disc and fundus photography and frequency doubling perimetry/ SITA Standard. Blindness was defined using WHO criteria as a best corrected visual acuity of 4/40 or worse and/or visual field of less than 10 degrees in the better eye on Sita Standard. The prevalence of different causes of blindness was calculated for individual eyes and for each subject. The influence of age, gender, literacy and employment was assessed using multiple logistic regression. Results: 132 subjects (3.36%, 95%CI : 2.80,3.93) were diagnosed to be blind as defined. Unoperated cataract was responsible for blindness in 74.5% of eyes, glaucoma, optic atrophy and corneal scars accounted for 3.78 % each. Other leading causes included cystoid macular edema, macular disease, corneal decompensation, ARMD and retinitis pigmentosa. Bilateral causes of blindness were cataract (69.7%), glaucoma (3.78%), optic atrophy (3.03%) and cystoid macular edema, macular scars and corneal scars (2.27% each). Blindness was significantly positively associated with increasing age (p<0.0001). Gender, literacy and employment did not show any association with blindness. Conclusions: 3.36% of the studied rural population were bilaterally blind, with cataract being the single most important cause.