Blindness and eye diseases in Tibet: findings from a randomised, population based survey

Background: Public health officials of the Tibet Autonomous Region ( TAR) of China requested a survey of blindness, eye diseases, and eye care service utilisation to assist the development of a 10 year blindness prevention and treatment plan. The objective of the survey was to determine the prevalence of blindness and visual impairment, as well as cataract surgical coverage and surgical outcome in the TAR. Methods: The Tibet Eye Care Assessment was a cross sectional prevalence study of three of the seven prefectures ( provinces) of the TAR ( Lhoka, Nakchu, and Lingzhr) selected to represent its three main environmental regions. The survey sample was selected using a random multistage cluster method. Two teams conducted the survey in a standardised fashion in each prefecture, Lhoka during May and Nakchu during June 1999, and Lingzhr during May 2000. Visual acuity, cause of vision loss, trachoma, and vitamin A deficiency were included in the clinical examination. Results: Among the 15 900 people enumerated, 12 644 were examined for an overall response rate of 79.6%. The crude prevalence of blindness ( presenting better eye visual acuity of less than 6/60) was 2.3%; age and sex adjusted blindness prevalence was 1.4% ( 95% CI 1.3 to 1.5). Visual impairment ( better eye presenting visual acuity of 6/24 to 6/60) was found in 10.9% ( 95% CI 10.5 to 11.2) of the population ( age and sex adjusted). Cataract was the primary cause of blindness (50.7%), followed by macular degeneration (12.7%) and corneal opacity (9.7%). Conclusion: Blindness is a serious public health problem in Tibet, with prevalence higher than in similar studies in eastern China. As elsewhere in the world, women have an excess burden of blindness compared to men. About 75% of blindness in Tibet can be either prevented or treated. Eye care planning for Tibet must focus on cataract, particularly among women.