A cataract is a clouding of the lens in the eye that affects vision.  Most cataracts are related to aging.  Cataracts are very common in older people.  By age 80, more than half of all Americans either have a cataract or have had cataract surgery.

A cataract can occur in either or both eyes.  It cannot spread from one eye to the other.

In a normal eye, light passes through the transparent lens to the retina.  Once it reaches the retina, light is changed into nerve signals that are sent to the brain.

The lens must be clear for the retina to receive a sharp image.  If the lens is cloudy from a cataract, the image you see will be blurred.  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 cataracts, 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.

Cataracts tend to “grow” slowly, so vision gets worse gradually.  Over time, the cloudy area in the lens may get larger, and the cataract may increase in size.

The risk of cataracts increases as you get older.  Other risk factors for cataracts include:

• Certain diseases (for example, diabetes)
• Personal behavior (smoking, alcohol use)
• The environment (prolonged exposure to ultraviolet sunlight)
  The most common symptoms of a cataract are:
• Cloudy or blurry vision
• Colors seem faded
• Glare. Headlights, lamps or sunlight may appear too bright.  A halo may appear around lights.
• Poor night vision
• Double vision or multiple images in one eye. (This symptom may clear as the cataract gets larger).
• Frequent prescription changes in your eyeglasses or contact lenses.
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• These symptoms also can be a sign of other eye problems. If you have any of these symptoms, check with your eye care professional. The symptoms of early cataracts may be improved with new eyeglasses, brighter lighting, anti-glare sunglasses, or magnifying lenses. If these measures do not help, surgery is the only effective treatment. Surgery involves removing the cloudy lens and replacing it with an artificial lens.

• A cataract needs to be removed only when vision loss interferes with your everyday activities, such as driving, reading, or watching TV.

• You and your eye care professional can make an informed decision about whether cataract surgery is right for you. In most cases, delaying cataract surgery will not cause long-term damage to your eye or make the surgery more difficult. You do not have to rush into surgery. Cataract removal is one of the most common operations performed in the United States. It also is one of the safest and most effective types of surgery. In about 90 percent of cases, people who have cataract surgery have better vision afterward. Many people who need cataract surgery also have other eye conditions, such as age-related macular degeneration or glaucoma. If you have other eye conditions in addition to a cataract, talk with your doctor. Learn about the risks, benefits, alternatives, and expected results of cataract surgery. Wearing sunglasses and a hat with a brim to block ultraviolet sunlight may help to delay the development of cataracts. If you smoke, stop. Researchers also believe good nutrition can help reduce the risk or age-related cataracts. They recommend eating green leafy vegetables, fruit, and other foods with antioxidants. If you are age 60 or older, you should have a comprehensive dilated eye exam at least once every two years. In addition to cataracts, your eye care professional can check for signs of age-related macular degeneration, glaucoma, and other vision disorders. Early treatment for many eye diseases may save your sight.This information was developed by The National Eye Institute.