Prevalence and causes of blindness and visual impairment in Mongolia: a survey of populations aged 40 years and older.

The survey was conducted in 3 out of the 18 administrative regions (aimaks); 4345 people aged > or = 40 years were examined, which represented 95.7% of the proposed sample. The prevalences of blindness and low vision in the sample were 1.5% (95% CI, 0.8-2.3%) and 8.1% (95% CI, 5.5-10.7%), respectively, from which the prevalences of blindness and low vision in the Mongolian population aged 40 years and older were estimated to be 1.4% and 7.7%, respectively. The prevalence of climatic droplet keratopathy was high (ranging from 15% to 50%) in this population, which included a large number of semi-nomadic cattle breeders, and was responsible for 7.2% of the blindness and 19.3% of the low vision. Cataract and glaucoma were the commonest blinding disorders, each accounting for around 35% of the blindness. Trauma accounts for a high proportion of those monocularly blind. Trachoma and xerophthalmia were not found.