[Cataract epidemiology survey in the three climatically different areas in Japan--prevalence of cataracts and types of lens opacification].

A cataract epidemiology study of 1,615 subjects from three climatically different places in Japan, village S in Hokkaido, town M in Noto and village Y in Okinawa, was conducted by one study group. Cataract diagnosis and grading of cataracts were objectively done with a photo-documentation system. The percentages of cataracts of over grade I classified by the Japanese Cooperative Cataract Epidemiology Study Group were 46.6%, 64.6% and 38.0% in village S, town M, and village Y, respectively. Those in their 50s, 60s, and 70s in the above places were 24.3%, 51.1% and 71.4% (village S), 38.4%, 65.3% and 84.6% (town M), and 25.2%, 42.9% and 65.4% (village Y), respectively. Cortical cataract was the most common, followed by nuclear and subcapsular types. Although the highest percentage of nuclear cataracts was seen in the subjects of village Y, subcapsular cataract was seen almost equally in the three areas. Lens transparency changes were evaluated by the light scattering intensities in the lens layers through photographed images. Intensity increased with ageing either linearly or exponentially.