To determine the causes of monocular blindness in the study population and to suggest actions for prevention and treatment.

A cross-sectional study was conducted among patients that presented to Shafa hospital eye clinic (Kerman-Iran) over a period of 18 months (March 2014-September 2015), with visual acuity (VA) less than 3/60 in the worse eye after optical correction. Visual acuity was determined using snellen chart, and full ocular examination including anterior and posterior segment evaluation was done. The data was documented in a questionnaire designed for the study.

Over study period, 486 patients presented with monocular blindness. 280 (57.6%) males and 206 (42.4%) females (Male to female ratio of 1.3).Their ages ranged from 2 to 92 years (55.3±20.5). The leading cause of monocular blindness was cataract (27%) followed by trauma (20%). Other causes were complications of cataract surgery (8%), glaucoma (7%), corneal opacity (6%), AMD (4%), amblyopia (4%), complications of diabetes mellitus (4%), keratoconus (3%), retinal detachment (3%), retinal vascular problems (3%), and childhood infections (2%). Other causes included 9% of cases. 80% of monocular blindness causes were avoidable (preventable or treatable).

Cataract followed by trauma are the two leading causes of monocular blindness. Most cases are avoidable.