A cataract describes any opacity of the normally transparent & avascular lens. Cataractogenesis occurs most commonly as a result of hereditary factors, however may also result from systemic disease (notably diabetes mellitus), lenticular trauma/inflammation, dietary deficiencies (notably associated with the use of milk-replacers), exposure to pharmacologic agents (notably ketoconazole), as a sequela to the retinal atrophies (RAs) & following exposure to therapeutic radiation. Changes may be unilateral or bilateral, symmetrical or asymmetrical and may develop over varying timeframes.