Cataracts develop when the lens of the eye becomes cloudy. They usually impair vision and most often occur as people get older.

In a normal eye, the lens of an eye is clear. If the lens is cloudy (center of the eye) from a cataract, the image seen will be blurred.

In a normal eye, the lens of an eye is clear. If the lens is cloudy (center of the eye) from a cataract, the image seen will be blurred.

What Are Cataracts?

Many people who live to an old age develop cataracts, often without noticing the effects until they are past age 70. For some, it might mean only a slight change in vision. Others, however, find they need surgery to remove the cloudy lens.

A cataract results when the clear lens in the eye becomes cloudy. Like frost on a window, the cataract makes it more difficult to see clearly. The reason is that the light passing through the cloudy lens is distorted before it reaches the visual receptors in the retina * at the inside rear of the eyeball.

What Happens When People Get Cataracts?

Researchers believe that cataracts develop because the proteins in the eye change as people age. The changes cause the lens to become cloudy. Other factors, such as smoking, poor nutrition, eye injury, exposure to excessive sunlight, and certain medical conditions such as diabetes * , may be factors that put people at higher risk of developing cataracts.

Cataracts develop slowly. At first, people notice difficulty reading the newspaper, or they experience blurry vision. The eyes become more sensitive to light, and seeing at night becomes especially difficult. People with cataracts often say they feel like they have a film over their eyes, as if they are looking through a piece of gauze.

For a short time, the condition actually may benefit some people who have had trouble seeing objects that are near them, such as the words on a page. The cloudiness of a cataract changes how light is focused and temporarily results in better vision for such people. They may find themselves able to read for the first time without eyeglasses, a condition sometimes called second sight. As the cataracts worsen, however, eventually these people experience increasing visual difficulties.

How Do Doctors Diagnose and Treat Cataracts?

An ophthalmologist * examines the eye to detect a cataract and follow its progress. When cataracts are detected, the doctor evaluates the symptoms and recommends the best course of treatment.

Many people can live with the condition untreated. For others, surgery may be recommended to remove the cloudy lens and to replace it with a clear artificial lens that is smaller in size than a dime. Cataract surgery improves vision in 90 to 95 percent of cases. It is one of the most common operations, with more than 1 million performed each year. Surgery generally is done when the lens has become so opaque or cloudy that reading, driving, or watching television are major problems.

Cataracts develop slowly, causing the eye's clear lens to become cloudy. Cataracts can be removed surgically.

Cataracts develop slowly, causing the eye's clear lens to become cloudy. Cataracts can be removed surgically.
Illustration by Frank Forney. © 2016 Cengage Learning®.

Can Cataracts Be Prevented?

Some studies suggest that vitamins C and E may lower the likelihood of developing cataracts. That is because these vitamins appear to reduce damage to the proteins that are linked to the development of cataracts. Regularly wearing sunglasses that block ultraviolet * light may also lower a person's risk of developing cataracts because studies strongly suggest that sunlight plays a role in their development. Avoiding cataracts is another important reason to avoid smoking, as smokers appear to have an increased risk of developing cataracts.

See also Aging • Eye Disorders: Overview


Books and Articles

World Health Organization. “Visual Impairment and Blindness.” WHO Fact Sheet No. 282. Updated August 2014. (accessed November 27, 2015).


National Eye Institute. “Facts about Cataracts.” National Institutes for Health. (accessed November 27, 2015).


American Optometric Association. 1505 Prince St., Suite 300, Alexandria, VA 22314-2874. Toll-free: 800-365-2219. Website: (accessed November 27, 2015).

Prevent Blindness. 211 W. Wacker Dr., Suite 1700, Chicago, IL 60606. Toll-free: 800-331-2020. Website: (accessed November 27, 2015).

* retina (REH-tuh-na) is the tissue that forms at the inner surface of the back of the eyeballs. It receives the light that enters the eye and transmits it through the optic nerves to the brain to produce visual images.

* diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.

* ophthalmologist (off-thal-MOLLo-jist) is a medical doctor who specializes in treating diseases of the eye.

* ultraviolet is a wavelength of light beyond visible light; on the spectrum of light, it falls between the violet end of visible light and x-rays.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)