To determine the prevalence of visual impairment and blindness and related factors in the 1-90 year old urban population of Mashhad

In this cross-sectional study of over-1 year old residents of Mashhad city in northeast Iran, sampling was done through random stratified cluster sampling. After selecting the samples and their participation in the study, all subjects had vision testing including measurement of visual acuity and refraction, the cover test, as well as examinations with the slit lamp and ophthalmoscopy

Of the 4453 selected persons, 3132 (70.4%) participated in the study. The prevalence of visual impairment based on presenting vision and vision corrected was 3.95% (95%CI: 3.13-4.77) and 2.23 (95%CI:1.54-2.91), respectively. The prevalence of presenting visual impairment increased from 1.59% in children under 5 years of age to 43.59% in people older than 65 years of age; these figures were respectively 1.59% and 42.31% based on corrected visual acuity. In the logistic regression model, older age, lower education, and low income correlated with impaired sight. Based on presenting vision and best corrected vision, the prevalence of blindness was 0.86% (95%CI: 0.51-1.22) and 0.32% (95%CI: 0.1-0.55). The most common causes of visual impairment were uncorrected refractive error (41.8%) and cataract (20%)

The prevalence of visual impairment and blindness in the present study was average; nonetheless, refractive errors and cataracts remain as the main causes of impaired vision and blindness in this population, while these two conditions are easily treatable with correction or surgery