Cataracts is characterised by cloudiness or opacity in the lens of a person's eye which interferes with the clear focusing of images on the retina. Your eyes are constantly exposed to many chemicals, irritants and pollution, many of which may cause oxidative stress. Oxidative damage contributes to the formation of cataracts. (Even passive smoking!) Decreased vitamin C levels in the lens of the eye have been associated with increased severity of cataracts. Citations and References may be found here.