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, and decreased vision, contrast, and color sensitivity.
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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:
- Aging, the most common cause
- Certain infections
- Exposure to radiation, certain toxins, or medications
- Taking adrenal cortical hormones for a long time
- Birth defect, inborn error of metabolism, or chromosomal abnormality
A risk factor is something that increases your chance of getting a disease or condition.
Risk factors for cataracts 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.
- Cloudy or blurry vision
- Colors seem faded or images appear with a yellow tint
- Poor contrast
- Poor night vision
- Difficulty reading
- Double or multiple vision (this symptom often goes away as the cataract matures)
- Increased nearsightedness, requiring frequent changes in your eyeglass or contact lens prescription
Problems with light, including
- Headlights that seem too bright at night
- Glare from lamps or very bright sunlight
- A halo around lights
- Trying to read in bright light
- Problems when moving from a dark area to a bright area
- Colors seem faded
- Poor night vision
- In rare cases, a cataract may cause an acute glaucoma attack.
These symptoms can also be signs of other eye problems. If you have any of these symptoms, check with your eye care professional immediately.
Although you might think you have a cataract, the only way to know for sure is to have an eye examination. To detect a cataract, an ophthalmologist or optometrist examines the lens and may do other tests to learn more about the structure and health of your eye.
A comprehensive eye examination for cataracts usually includes:
- Visual Acuity Test—This eye chart test measures how well you see at various distances. This may include a test of your vision under conditions of low contrast and/or glare.
- Slit Lamp Exam—This is an examination of the eye using a specialized microscope that magnifies the eye.
- Tonometry—This is a standard test to measure fluid pressure inside the eye. Increased pressure may be a sign of glaucoma.
- Dilated Eye Exam—The doctor gives you special eye drops to widen your pupil, which allows better examination of the lens and the structures of the back of the eye. This allows your doctor to examine the lens in more detail to detect a cataract.
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.
is almost never an emergency. Therefore, in most cases, waiting until you are ready to have cataract surgery will not harm your eye. However, your cataract will only 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 (ophthalmologist) 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, and many people need glasses 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 patients who receive multifocal intraocular lenses see well at both a distance and nearby without glasses.
Although every surgery has risks, the majority of patients who have cataract surgery have better vision afterward.
If you are diagnosed with cataracts, follow your doctor's
Although there is no way to completely prevent cataracts, the following precautions may help:
- Do not smoke.
- Consume antioxidants, such as antioxidant vitamin supplements.
- Wear a hat and UV-protected sunglasses when outdoors.
- Follow your doctor's instructions to keep any chronic diseases in good control.
It is also important to get a comprehensive eye examination regularly. Since vision problems increase with age, if you are aged 60 or older, you should have a comprehensive eye examination once a year.
American Academy of Ophthalmology
National Eye Institute, NIH
The College of Family Physicians of Canada
Canadian Ophthalmological Society
Cataracts. National Eye Institute. National Institutes of Health website. Available at:
http://www.nei.nih.gov/health/cataract. Updated May 2009. Accessed July 13, 2009.
National Institutes of Health.
Ophthalmic Genetics Newsletter.