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

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.

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

Vision problems associated with cataracts generally move towards 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 slight visual 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.

The only treatment for cataract is surgery to remove it. This is done if you cannot perform normal activities, even with glasses.

If a cataract is not bothersome, then surgery is usually not necessary. However, there may be an additional eye problem that cannot be treated without first having cataract surgery.

For some people, changing glasses, getting stronger bifocals, or using a magnifying lens is helpful enough.

For information on surgery, see: Cataract surgery

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.

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.