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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

Lens opacity

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 very gradually with advancing age and may run in families. They develop slowly and painlessly, and vision in the affected eye or eyes slowly gets worse.

Cataracts develop more quickly if there are some environmental factors, such as smoking, exposure to other toxic substances, and exposure to excessive ultraviolet light or sunlight. 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.

• Immature cataract -- lens has some remaining clear areas
• Mature cataract -- completely cloudy, or opaque lens, which means you can't see through it
• Hypermature cataract -- lens tissues are breaking down and leaking through the surface covering, which can damage other structures in the eye

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

Factors that may contribute to cataract development are:

• Diseases that cause inflammation or affect metabolism
• Eye injury
• Family history
• Long-term use of corticosteroids or certain other medications
• Radiation exposure
• Smoking
• Too much exposure to ultraviolet light (sunlight)

In many cases, the cause of cataract is unknown.

Watch this video about: Cataract

Visual problems may include the following changes:

• Cloudy, fuzzy, foggy, or filmy vision
• Loss of color intensity
• Double vision
• Difficulty seeing at night
• Problems seeing shapes against a background or the difference between shades of colors
• Seeing halos around lights
• Being sensitive to glare

Cataracts generally lead to decreased vision, even in daylight. 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 mild vision changes.

Other symptoms may include:

• Frequent changes in eyeglass prescription

A standard eye exam and slit lamp examination are used to diagnose cataracts. Other diagnostic tests are rarely needed.

Vision may not improve to 20/20 after cataract surgery if other eye diseases, such as macular degeneration, are present. Ophthalmologists can usually, but not always, determine this in advance.

Early diagnosis and treatment are key to preventing permanent vision problems.

Call for an appointment with your health care provider if you have vision loss, decreased night vision, or problems with glare.

The best prevention involves controlling diseases that increase the risk of a cataract, and avoiding exposure to factors known to promote cataract formation.

Wearing sunglasses when you are outside during the day can reduce the amount of UV light your eyes are exposed to. Some sunglasses do not filter out the harmful UV. An optician should be able to tell you which sunglasses filter out the most UV. For patients who smoke cigarettes, quitting will decrease the risk of cataracts.

American Academy of Ophthalmology Preferred Practice Pattern: Cataract in the Adult Eye.

Olitsky SE, Hug D, Smith LP. Abnormalities of the Lens. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap. 627.