Rapid assessment of avoidable blindness in Iran

Abstract

Purpose: To determine the extent and causes of blindness and visual impairment (VI) in the Varamin district, Iran, in 2009.

Design: Cross-sectional population-based survey.

Participants: A total of 3000 noninstitutional inhabitants aged ≥50 years from February to August 2009.

Methods: A standard protocol was used according to the rapid assessment of avoidable blindness (RAAB) method after an initial 4-day workshop. The clusters were selected through probability-proportionate-to-size sampling. In each cluster, people were selected by a "cluster compact sampling" method. Visual acuity (VA) was measured using a standard tumbling "E" chart without and with pinhole. Ophthalmologists examined participants with VA <6/18 in either eye. Blindness was verified by the World Health Organization definition (best-corrected VA in the better eye <3/60). Severe VI (SVI) was defined as VA ≥3/60 and <6/60 and VI was defined as VA ≥6/60 and <6/18 at presentation. The primary cause of VI was defined according to the cause in the participant's better eye.

Main outcome measures: Prevalence of blindness, SVI, and VI, and their avoidable causes.

Results: Among 3000 persons, 2819 (94% response rate), including 1289 men (45.1%) and 1530 women (54.9%), were examined. The standardized prevalence rates of blindness, SVI, and VI were 1.33 (95% confidence interval [CI], 0.91-1.75), 1.39 (95% CI, 0.81-1.97), and 6.91 (95% CI, 5.96-7.86), respectively, and the prevalence rates of avoidable causes (cataract, surgical complication, refractive error, and corneal scar) of blindness, SVI, and VI were 56.1%, 65.0%, and 85.6%, respectively. The principal cause of blindness and SVI was cataract, and the principal cause of VI was refractive error.

Conclusions: Most blindness, SVI, and VI is due to avoidable causes. Cataract and refractive errors were the leading causes in our context.