Cataracts are changes in the clarity of the lens so that it appears cloudy. Such changes are a clinical or gross diagnosis, and there may be no histopathological correlate. Nevertheless, opacity of the lens results in reduced ability to see. Cataracts may be divided into primary or secondary disease. In primary cataract, opacity of the lens is the only sign of disease in the eye, while in secondary cataract the lens changes occur as a consequence of other intraocular disease. A wide variety of causes...