Cataract

Pictures & Images

See all Pictures & Images

Overview, Causes, & Risk Factors

The lens of an 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. Cataracts are accelerated by environmental factors, such as smoking or exposure to other toxic substances, or they may develop at any time after an eye injury. Metabolic diseases such as diabetes also greatly increase the risk for cataracts. Certain medications, such as cortisone, can also accelerate cataract formation.

Congenital cataracts may be inherited. The gene for such cataracts is dominant (autosomal dominant inheritance), which means that the defective gene will cause the condition even if only one parent passes it along. Approximately 50% of children in such families will be affected.

Congenital cataracts can also be caused by infections of the mother during pregnancy such as rubella, or associated with metabolic disorders such as galactosemia. Risk factors include inherited metabolic diseases, a family history of cataracts, and maternal viral infection.

Adult cataracts are generally associated with aging. They develop slowly and painlessly with a gradual onset of difficulty with vision.

Visual problems may include the following changes:

• Difficulty seeing at night
• Seeing halos around lights
• Being sensitive to glare

Vision problems associated with cataracts generally progress to decreased visual acuity, even in daylight.

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 opaque. A hypermature cataract has a liquefied surface that leaks through the capsule and may cause inflammation of other structures in the eye.

Most people develop some clouding of the lens after the age of 60. About 50 percent of people aged 65 to 74 and about 70 percent of those 75 and older have visually significant cataracts. Most people with cataracts have similar changes in both eyes, although one eye may be worse than the other. Many people with this condition have only minimal visual changes and are not aware of their cataracts.

Factors that may contribute to cataract development are low serum calcium levels, diabetes, long-term use of corticosteroids, and various inflammatory and metabolic disorders. Environmental causes include trauma, radiation exposure, and excessive exposure to ultraviolet light (sunlight).

In many cases, the cause of cataract is unknown.