A cataract is a clouding of the lens of the eye. This clouding can impair vision.
What causes cataracts?
The eye functions much like a camera. Light rays enter through the front of the eye, passing through the cornea, the pupil, and the aqueous humor -- transparent fluid in the front of the eye -- onto the lens. The lens then bends light rays to focus objects onto the retina in the back of the eye. From there, the retina, the optic nerve, and the brain process the images and form vision.
Cataracts occur when there is a buildup of protein in the lens that makes it cloudy. This prevents light from passing through a normally clear lens, causing some loss of vision. The cause of the protein buildup responsible for clouding the lens is not known.
Types of cataracts include:
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Age-related cataracts:
As the name suggests, this type of cataract develops as a result of aging.
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Congenital cataracts:
Babies are sometimes born with cataracts as a result of an infection they had in the womb. Or, the cataracts may develop during childhood.
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Secondary cataracts:
These may develop as a result of other diseases, like diabetes, or long-term exposure to toxic substances, certain medications (such as corticosteroids or diuretics), ultraviolet light, and radiation.
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Traumatic cataracts:
These can form after injury to the eye.
Other factors that increase the risk of developing cataracts include cigarette smoke, air pollution, and heavy alcohol use.
What are the symptoms of cataracts?
Cataracts often form slowly and cause few symptoms. When symptoms are present, they can include:
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Vision that is cloudy, blurry, foggy, or filmy
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Sudden nearsightedness
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Changes in the way you see color, especially yellow
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Problems driving at night because oncoming headlights are distracting
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Problems with glare
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Double vision
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Sudden temporary improvement in close-up vision
How are cataracts diagnosed?
A series of simple tests performed by your eye doctor can diagnose cataracts. An eye exam will be given to test how well you can see (remember to bring your glasses or wear your contacts). Your doctor will also dilate your pupil in order to examine the condition of the lens and other parts of the eye.
How are cataracts treated?
The eye exam will tell your eye doctor how much vision loss is present. If the loss is minimal, your doctor may prescribe eyeglasses (including bifocals), magnification devices, contacts, or other visual aids.
If you suffer from severe vision loss that impairs your daily life, you may be a candidate for cataract surgery. This surgery involves removing the clouded lens and replacing it with a clear, plastic one.
Cataract surgery, usually conducted on an outpatient basis, is very successful in restoring vision. In fact, it is the most frequently performed surgery in the United States, with more than 1.5 million cataract surgeries each year. More than nine out of 10 people who have cataract surgery regain excellent vision.
Talk to your doctor to see which treatment is right for you.
Can cataracts be prevented?
Because the exact cause of cataracts is uncertain, there is no proven method to prevent them from forming.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/20/2003
