Cataract is clouding of the eye lens. The lens is made up of mainly water and protein. Over time, protein can build up, clouding the lens and obstructing and diffusing the light passing through the eye. This makes lens sight blurred or fuzzy which cannot be corrected by wearing glasses. Although most cases of cataract are related to the aging process, occasionally children can be born with the condition, or a cataract may develop after eye injuries, inflammation, and other eye diseases.

Cataract (not related to radiation) is the most frequent cause of blindness worldwide. There are several risk factors, including exposure to sunlight, ionizing radiation, alcohol and nicotine consumption, diabetes and systemic use of corticosteroids.