A cataract is a clouding of the eye's lens. It leads to decreased vision. The lens of the eye focuses an image onto the retina at the back of the eye. This is where an image is processed, and then sent to the brain.
As the cataract matures, it often causes glare, decreased vision, and contrast. Color sensitivity may also be lost if the cataract begins to turn yellow.
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The lens of the eye is made of mostly water and protein. The protein is arranged in a way that keeps the lens clear so light can pass through it. A cataract forms when some of the protein clumps together and starts to cloud an area of the lens. A cataract won't spread from one eye to the other, although most people develop cataracts in both eyes at similar times.
There are several causes of cataracts, including:
Cataracts are common in older adults. Other factors that may increase your chance of a cataract include:
When a cataract is in the early stages, you may not notice any changes in your vision. Cataracts tend to mature slowly. Vision gets worse gradually. Some people with a cataract find that their close-up vision suddenly improves. This is only temporary. Vision is likely to get worse as the cataract becomes cloudier. Because the decrease in vision is gradual, many people do not realize that they have a cataract until it is discovered during a routine eye examination.
A cataract may cause:
These symptoms can also be signs of other eye problems. If you have any of these symptoms, check with your eye care professional right away.
The only way to diagnose a cataract is to have an eye examination. Your eye doctor will examine the lens or do some tests to learn more about the structure and health of your eye.
A comprehensive eye examination for cataracts usually includes:
For an early cataract, vision may be improved by using different eyeglasses, magnifying lenses, or stronger lighting. If these measures don't help, or if vision loss interferes with daily activities such as driving, reading, or watching TV, surgery is the only effective treatment.
Cataract surgery involves waiting until you are ready to have to have it so that it doesn't harm your eye. While you wait, your cataract will get cloudier with time.
Cataract surgery is almost always performed in one eye at a time. After the cloudy lens is removed, the eye surgeon places an intraocular lens (IOL) in its place. An IOL is a clear lens that requires no care and becomes a permanent part of your eye.
After cataract surgery, most people need reading glasses or for distance vision. There is a relatively new option, multifocal intraocular lenses, which focus for both near and far distances in the same lens. Many who receive multifocal intraocular lenses may not need to wear glasses.
To help reduce your chance of a cataract:
Eye Smart—American Ophthalmology
National Eye Institute
Canadian National Institute for the Blind
Canadian Ophthalmological Society
Cataracts in adults. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116240/Cataracts-in-adults . Updated October 23, 2017. Accessed September December 14, 2017.
Cataracts. National Eye Institute website. Available at:
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Updated September 2015. Accessed December 14, 2017.
Last reviewed November 2018 by
EBSCO Medical Review Board
Michael Woods, MD, FAAP
Last Updated: 1/29/2018