A cataract is any clouding or opacity in the crystalline lens – the normally transparent lens inside the eye. A cataract is not a tumor or growth of skin over the eye. Having a cataract does not mean you will necessarily have to do anything about it or that you will eventually be blinded by it.

Most cataracts occur as part of the aging process, from a change in the chemical composition of the lens. They usually do not become a problem until you are in your 60s or 70s. (If you live long enough, you are almost certain to develop one eventually.) Some, but not all, scientists feel that prolonged exposure (over years) to sunlight can damage the lens and plays a role in cataract development.

Cataracts can also be caused by eye injuries, certain eye diseases and body conditions, hereditary or birth defects, and, occasionally, some medications. They are not caused or made worse by using or "overusing" the eyes.

You may have a cataract if you've noticed a gradual blurring or dimming of vision. Some people see a "halo" or haze around lights, especially at night, or have hazy or double (or multiple) vision. At first, the symptoms may occur only in dim light or when you face bright oncoming car headlights; the glare may make night driving especially difficult. Pain, headaches, and eye irritation are not usually symptoms of cataract.

If a cataract is small, it may not disturb your vision or cause any symptoms at all. Even a dense cataract may not be noticed if the other eye is providing clear vision. In fact, you might not be aware of the blurred vision unless you happened to cover the normal eye. Unless it is very dense, a cataract is not visible to the naked eye of an observer.

No one can predict how fast a cataract will develop. Generally, the clouding of the lens progresses slowly and gradually over a period of months or years. It is not known why some cataracts progress rapidly and others progress slowly.

At present, the only effective treatment is surgical removal of the cloudy lens. This can be done in a hospital or outpatient surgical suite. Some: studies hint that the process can be slowed by vitamin C or aspirin, but other treatments, such as medications or exercises, do not help at all.

If the cataract is minimal, treatment may be delayed for a while by changing your glasses prescription or by dilating (enlarging) your pupils.

Surgery has a 95 percent success rate. It is one of the most effective and safest operations performed today.