There are several causes of cataract. The most common form of cataract is associated with ageing, although not everyone develops cataracts as they get older. Cataracts may be caused by an eye injury: a sharp blow, a chemical or electrical burn or a very high dose of radiation. Rare causes of cataracts include side-effects of some long-term medications and eye diseases. Genetics can also rarely lead to the development of cataracts at birth or early in childhood.