• Definition

    A cataract is a clouding of the lens of the eye.

    This article focuses on cataracts in adults. For information on cataracts in children, see: Congenital cataracts

    Alternative Names

    Lens opacity; Age-related cataract

    Causes, incidence, and risk factors

    The lens of the eye is normally clear. It acts like the lens on a camera, focusing light as it passes to the back of the eye.

    Until a person is around age 45, the shape of the lens is able to change. This allows the lens to focus on an object, whether it is close or far away.

    As we age, proteins in the lens begin to break down and the lens becomes cloudy. What the eye sees may appear blurry. This condition is known as a cataract.

    Factors that may speed up cataract formation are:

    • Diabetes
    • Eye inflammation
    • Eye injury
    • Family history of cataracts
    • Long-term use of corticosteroids (taken by mouth) or certain other medications
    • Radiation exposure
    • Smoking
    • Surgery for another eye problem
    • Too much exposure to ultraviolet light (sunlight)

    In many cases, the cause of cataract is unknown.