[Epidemiology of Bietti's keratopathy. Study of risk factors in Central Africa (Chad)].

Climatic Droplet keratopathy (synonyms: spheroidal degeneration, Bietti's keratopathy) is a corneal degeneration characterized by an opacification at the level of the Bowman's membrane in the area of the palpebral fissure. It is particularly common in areas of bright sunlight and in Labrador; ultraviolet light thus being thought at its genesis. Two objectives were included in this study: studying the Climatic Droplet Keratopathy (CDK) prevalence by looking for the influence of the climatic factor; looking for possible association with three other degenerative ocular diseases: cataract, open-angle, glaucoma and exfoliation syndrome. A random cluster sampling survey was carried out in different climatic areas in Chad (N = 3,241 people). The resulting analysis showed a significant relation between the CDK prevalence and the kind of climate: the more the climate is dry; the more the higher the frequency: subdesert area = 1.57%, Sahelian area = 0.73%, tropical area = 0.18% (p less than 0.0001, rate standardized to age). The CDK occurs earlier in the subdesert area (mean age = 60.0) than in the Sahelian one (mean age = 66.7) (p less than 0.05). The CDK only exists among people age 40 or older, and is more frequent among males than females (p less than 0.005). The cataract is more frequent among individuals having a CDK than among those without it: relative risk = 4.3 (C.I.: 2.3-7.9 p less than 0.00001) (Mantel-Haenszel's method with adjustment to climate, age and sex). As for open-angle glaucoma, it is more frequent among individuals suffering from CDK: relative risk = 4.2 (p = 0.05). Finally, we noticed that the exfoliation syndrome was 5 times more frequent among chadians suffering from a CDK (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)