Caption

Cataract (centre) in the early stages of development. Cataract occurs when the lens of the eye changes in structure, becoming cloudy (opaque) and losing its normal transparency. It is a natural feature of ageing, but can also be caused by an eye injury, diabetes, some drugs and exposure to radiation. It leads to progressive loss of sight and may result in blindness. Treatment is by the removal of the lens and its replacement with an artificial lens.