The prevalence of cataract in two villages of northern Pakistan with different levels of ultraviolet radiation.

To study the effect of ultraviolet (UV) light on the development of age-related cataract, a community-based cross-sectional study was undertaken in two villages in the mountainous Northern Areas of Pakistan. The relative UV light exposure was calculated by the UK Universities Global Atmospheric Modelling Program using the variables direct sunlight hours per day, latitude and ground reflectivity. A total of 797 subjects (410 men, 387 women) over the age of 40 years from both villages were examined for the presence of cataract. The prevalence of cataract increased with age (p < 0.001) and was significantly higher in women at all ages (p < 0.01). There was no significant difference in the overall prevalence of cataract between the two villages. The male population in each village was subdivided into those who worked predominantly indoors and those who worked predominantly outdoors. All women worked outdoors. There was no significant difference in the prevalence of cataract between the male outdoor workers in the two villages. The indoor workers in the village with higher UV light exposure (Hunza) had a significantly higher cataract prevalence (p < 0.001) than the indoor workers in the village with lower UV light exposure (Nomol). In the village with lower UV light exposure (Nomol), the male outdoor workers had a significantly higher prevalence of cataract than the male indoor workers (p < 0.001). There was no significant difference in the prevalence of cataract between the male indoor and outdoor workers in the village with higher UV light exposure (Hunza). Overall, these results are not strongly supportive of UV light being of major importance in cataractogenesis, but they are consistent with a saturation model of UV light as a risk factor for cataract formation.