Prevalence and causes of low vision and blindness in Tehran Province, Iran.

OBJECTIVE To determine the prevalence and causes of blindness and low vision selected population at Tehran province, Iran in 2006. METHODS A population-based cross-sectional study was conducted in the rural and urban population of Tehran province, Iran. The study design was based on the World Health Organization (WHO) criteria and a pilot study. Multi-stage cluster random sampling method was used and sample size was calculated based on the distribution of population in Tehran province derived from the national census and estimated rate of blindness from the pilot study. Information was collected using a questionnaire filled after screening by optometrists and referral examinations by ophthalmologists. Categorization of blindness and low vision was based on the International Classification of Diseases version 10 (ICD-10). RESULTS Overall, 11,975 subjects with mean age of 27.77 +/- 18.9 years participated (primary response rate of 90.4%). The prevalence of bilateral blindness was 1.09% (95% CI: 0.90-1.61%). There was a significant positive correlation with age (P < 0.001) but no significant difference by gender. The prevalence of low vision in both eyes was 4.04% (95% CI: 3.69-4.39%). The prevalence of bilateral low vision increased with age (P < 0.001) and was higher among females (OR = 1.42, 95% CI: 1.16-1.74). The leading causes of visual impairment were cataract (33.9%), amblyopia due to uncorrected refractive errors (22.7%), vitreo-retinal diseases (12.3%), corneal blindness (10%) and diabetic retinopathy (4.92%). CONCLUSION The prevalence of blindness and low vision in Tehran province, Iran is similar to other developing countries. The majority of cases have treatable and/or preventable causes; reduction of blindness can be achieved by appropriate screening strategies.