Causes of Visual Impairment among Patients Referred to a Visual Rehabilitation Clinic in Iran

PURPOSE: Epidemiologic evaluation and investigating the causes of visual impairment in any society is a matter of concern and has a direct effect on the country's health care planning. In this study we describe causes of low vision and blindness in Iranian patients referred to rehabilitation clinics for taking vision aids. METHODS: In this cross-sectional study, visual acuity was classified based on best-corrected visual acuity in the better eye according to the World Health Organization definition (blindness, visual acuity [VA] < 20 / 400; severe visual impairment, VA < 20 / 200-20 / 400; mild to moderate visual impairment, VA < 20 / 60-20 / 200). The causes of blindness and low vision were determined using the 10th version of International Classification of Diseases based on the main cause in both eyes. To describe data, we used mean +/- SD and frequency. RESULTS: The study included 432 patients, 65% male, with a mean age of 43.6 +/- 25.5 years (range, 3 to 92 years). Mild to moderate visual impairment, severe visual impairment and blindness were present in 122 (28.8%), 196 (46.4%) and 105 (24.8%) of the patients, respectively. The main causes of visual impairment were retinal and choroidal diseases (74.5%), optic nerve and optic tract diseases (9.8%), vitreous and globe disorders (5.3%), congenital cataract (3.1%), and glaucoma (2.6%). The distribution pattern of the causes was similar in all age subgroups. CONCLUSIONS: Diseases of the retina and choroid are the main cause of visual impairment among patients referred to an academic visual rehabilitation clinic in Iran.

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.