Definition of Cataract:

A cataract is a cloudy area in the lens of the eye.

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

Causes, incidence, and risk factors:

The lens of the eye is normally clear. If the lens becomes cloudy, the condition is known as a cataract. Rarely, cataracts may be present at or shortly after birth. These are called congenital cataracts.

Adult cataracts usually develop with advancing age and may run in families. Adult cataracts are generally associated with aging. They develop slowly and painlessly, and vision in the affected eye or eyes slowly gets worse.

Cataracts develop more quickly in the presence of some environmental factors, such as smoking or exposure to other toxic substances. They may develop at any time after an eye injury. Diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also speed up cataract formation.

Adult cataracts are classified as immature, mature, and hypermature. A lens that has some remaining clear areas is referred to as an immature cataract. A mature cataract is completely cloudy, or opaque, which means you can't see through it. A hypermature cataract has leaking through the surface, which can lead to swelling and irritation of other structures in the eye.

Most people develop some clouding of the lens after the age of 60. About 50% of people aged 65-74, and about 70% of those 75 and older have cataracts that affect their vision.

Factors that may contribute to cataract development are:

• Disease that cause inflammation or affect metabolism
• Eye injury
• Low blood calcium levels
• Long-term use of corticosteroids
• Radiation exposure
• Too much exposure to ultraviolet light (sunlight)

In many cases, the cause of cataract is unknown.