Prevalence and causes of visual impairment and blindness in central Iran; The Yazd eye study

Purpose: To determine the prevalence and causes of blindness and visual impairment (VI) in Yazd, central Iran. Methods: This population-based, cross-sectional study was performed on adults aged 40-80 years, residing in Yazd district, in 2010-2011. Eligible subjects were selected using cluster random sampling. Each participant underwent an interview and complete ophthalmologic examination. Blindness and VI were defined as best-corrected visual acuity (VA) <3 /60 and < 6/18 in the better eye, respectively. Results: Out of 2,320 eligible individuals, 2,098 participated in the study (90.4% response rate), of whom, 2,023 subjects completed all evaluations. The standardized prevalence of blindness and VI were 0.7% (95% confidence interval [CI], 0.3-1.0%) and 4.4% (95% CI, 3.3-5.4%), respectively which was significantly associated with older age (odd ratio [OR] = 3.2, 95% CI: 1.9-5.2 and OR = 3.1, 95% CI: 2.3-4.2, respectively) and female sex (OR = 3.6, 95% CI: 1.1-12.3 and OR = 1.7, 95% CI: 1.2-2.5, respectively). The proportion of avoidable causes of blindness and VI were 92.9% (95% CI: 80.0-100.0%) and 76.6% (95% CI: 69.2-85.0%), respectively. Major causes of blindness were diabetic retinopathy (50.0%), glaucoma (21.4%) and cataracts (14.3%) whereas main causes of VI were cataracts (41.5%), diabetic retinopathy (17.0%) and age-related macular degeneration (13.8%). Conclusions: Diabetic retinopathy, glaucoma, cataract and age-related macular degeneration were the leading causes of blindness and VI in Yazd, most of which are avoidable. Planning for prevention of blindness is highly recommended to decrease the proportion of avoidable blindness.