3World Health Organization. Internation statistical classification of diseases and related health problem. Tenth revision.Vol 1. Geneva:World Health Organization,1992.
4Liu JH,Cheng CY,Chen SJ,et al.Visual impairment in a Taiwan Residents population: prevalence, causes, and socioeconomic factors. Ophthalmic Epidemiol, 2001,8:339-350.
5Taylor HR, Livingston FPM, Stanislavsky BYL, et al. Visual impairment in Australia:distance visual acuity, near vision, and visual field findings of the Melbourne Visual Impairment Project. Am J Ophthalmol, 1997, 123: 328-337.
6Hyman L, Wu SY, Connell AMS, et al. Prevalence and causes of visual impairment in the Barbados Eye Study. Ophthalmology, 2001, 108: 1751- 1756.
7Buch H, Vinding T, Nielsen NV. Prevalence and causes of visual impairment according to World Health Organization and United States criteria in an aged, urban Scandinavian population. Ophthalmol, 2001, 108: 2347-2357.
8Buch H, Morten V, Cour ML, et al. The prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population.The Copenhagen City Eye Study. Acta Ophthalmol Scand, 2001,79:441-449.
9Munoz B, West SK, Rubin GS, et al. Causes of blindness and visual impairment in a population of older Americans. Arch Ophthalmol, 2000,118:819-825.
10Faran MF, Rajhi AA, Omar OM, et al. Prevalence and causes of visual impairment and blindness in the south western region of Saudi Arabia. Int Ophthalmol, 1993,17:161-165.