Caption

Cataract. Close-up of the left eye of an elderly patient with a corticonuclear cataract. Cataracts are a clouding of the lens of the eye caused by the gradual denaturation of the proteins that make up the eye's lens. They never cause complete blindness but, as transparency of the lens is reduced over time, clarity and detail in sight is progressively lost. Ageing is the most common cause, however diseases such as diabetes, drugs such as steroids and trauma induced by injury or radiation are other causes. Congenital cataracts are rare. Surgery is an effective treatment.