A cataract is a clouding of the eye's lens that causes loss of vision. This brochure is about age-related cataract, the most common type.

What causes it?

The lens lies behind the iris and the pupil (see diagram). It works much like a camera lens. It focuses light onto the retina at the back of the eye, where an image is recorded. The lens also adjusts the eye's focus, letting us see things clearly both up close and far away.

The lens is made of mostly water and protein. The protein is arranged in a precise way that keeps the lens clear and lets light pass through it.

But as we age, some of the protein may clump together and start to cloud a small area of the lens. This is a cataract. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see.

Researchers suspect that there are several causes of cataract, such as smoking and diabetes. Or, it may be that the protein in the lens just changes from the wear and tear it takes over the years.

The term "age-related" is a little misleading. You don't have to be a senior citizen to get this type of cataract. In fact, people can have an age-related cataract in their 40s and 50s. But during middle age, most cataracts are small and do not affect vision. It is after age 60 that most cataracts steal vision.

A cataract starts out small. It has little effect on vision at first. You may notice that your vision is blurred a little, like looking through a cloudy piece of glass.

A cataract may make light from the sun or a lamp seem too bright, causing a glare. Or, you may notice when you drive at night that the oncoming headlights cause more glare than before. Also, colors may not appear as bright to you as they once did.

As the cataract gets bigger and clouds more of the lens (doctors use the term, "ripens"), you will find it harder to read and do other normal tasks. The word "cataract" means waterfall. For people with a ripe cataract, it is like trying to see through a waterfall.

Although you might think you have a cataract, the only way to know for sure is by having an eye examination. Should your eye care professional find one, he or she can monitor it and advise you about any future treatment.

If your eye care professional finds a cataract, you may not need cataract surgery for several years. In fact, you might never need cataract surgery. By having your vision tested regularly, you and your eye care professional can discuss if and when you might need treatment.

The National Eye Institute (NEI), one of the Federal government's National Institutes of Health, supports research on the lens and age-related cataract. Most of these studies focus on controlling cataract with drugs so that surgery will not be needed. Although these drugs are not yet available to patients, research is moving forward in this area. The NEI is also evaluating whether certain vitamins and minerals might prevent or slow the progress of cataract. We should know more about whether this treatment works in the coming years.

If you are over age 60, you should have an eye examination at least once every two years. This exam should include dilating your pupils. This means drops are put into your eyes to enlarge your pupils. Although a cataract can be detected without dilated pupils, your eye care professional can see the back of your eye better using this exam. Getting a good view of the retina and optic nerve is important in detecting eye diseases such as glaucoma and macular degeneration.

To learn more about cataract write: National Eye Health Education Program, 2020 Vision Place, Bethesda, MD 20892-3655.

April 2000