[Data analysis on epidemiologic survey of cataract in China]

To approach the prevalence of age-related cataract and its relationships with the condition of examination, diagnostic criteria and geographical environment in various areas.

According to the WHO's criteria of blindness and low vision, a statistical analysis of a national sample survey of blindness and low vision was carried out over the country.

The number of patients with age-related cataract and visual acuity < 0.3 in both eyes calculated in the whole population was more than 5 million, the prevalence being 0.46%. The prevalence of blindness and that of low vision were 0.43% and 0.58% respectively. Among the blind, 41.06% was caused by cataract, and the low vision caused by cataract was 49.38%. Among elderly of >or= 60 years, the proportion of the blind and low vision caused by cataract was 73.13%. When the cataract standard was defined as lens opacity with visual acuity < 0.7, the prevalence of cataract was 5.99% in Beijing sample survey at the suburb area. The incidence of age-related cataract in females was significantly higher than that in males. In a survey of Beijing suburb in 1997, the prevalence of cataract among 5,084 elderly people of >or= 50 years with bilateral corrected visual acuity < 0.1 was 2.22%. In the southern part of China, the area of low latitude, especially in the plateau, such as in Guangdong Province (0.69%) and in Tibet (1.04%), the prevalence of cataract is much higher than that in northern part, high latitude areas, such as Heilongjiang Province (0.26%). A comparative study of the cataract prevalence of elderly >or= 40 years in the areas of different levels above the sea and sunshine times, it shows that the higher level above the sea and longer sunshine time the higher cataract prevalence.

A longer sunshine time and a larger amount of ultraviolet irradiation are considered as the risk factors of cataract. Age-related cataract is the leading cause of blindness and the low vision in China.