title: Age-related cataract in the Tibet Eye Study.
abstract: The Tibet Eye Study was designed to estimate the prevalence of age-related cataract in Duilong-Deqing County, west of Lhasa, China (altitude, 4000 m). Previous reports have suggested an unusually high prevalence of age-related cataract in Tibet. A two-stage probability sample of persons aged 20 years or older from the 35 townships of the county targeted 2884 persons for inclusion in the study; 2665 (92.4%) were examined. Age-related cataract was diagnosed when (1) visual acuity was worse than 6/12 (20/40) because of nuclear or cortical (including posterior subcapsular) opacities, or (2) aphakia associated with a history of age-related cataract was present in either eye. The prevalence of age-related cataract among persons aged 20 to 39 years was 0.2%; among persons 40 years old or older, the prevalence was 11.8%. Cortical cataracts were by far the most common type of cataract diagnosed. Age- and sex-adjusted prevalence in Tibet was 60% higher than the prevalence in a similar, previously conducted study of 6951 person in Shunyi County, northeast of Beijing (altitude, 50 m). A second, independent slit-lamp classification of lens status was conducted in the Tibet Eye Study using standard photographs previously described. Age-specific cataract prevalence was similar with the two examination techniques. Results from the Tibet Eye Study support previous suggestions of a high prevalence of age-related cataract in Tibet.
authors.affiliation: Peking Union Medical College Hospital, Beijing, China.
authors.forename: T S
authors.initials: TS
authors.lastname: Hu
authors.forename: Q
authors.initials: Q
authors.lastname: Zhen
authors.forename: R D
authors.initials: RD
authors.lastname: Sperduto
authors.forename: J L
authors.initials: JL
authors.lastname: Zhao
authors.forename: R C
authors.initials: RC
authors.lastname: Milton
authors.forename: A
authors.initials: A
authors.lastname: Nakajima
mesh_terms: D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D002386:Cataract / Q000453:epidemiology / Q000209:etiology*; D002681:China; D006801:Humans; D008875:Middle Aged