A cataract is a clouding of the lens of the eye.
This article focuses on cataracts in adults. For information on cataracts in
children, see: Congenital cataracts
Causes, incidence, and risk factors
The lens of the eye is normally clear. It acts like the lens on a camera,
focusing light as it passes to the back of the eye.
Until a person is around age 45, the shape of the lens is able to change.
This allows the lens to focus on an object, whether it is close or far away.
As we age, proteins in the lens begin to break down and the lens becomes
cloudy. What the eye sees may appear blurry. This condition is known as a
Factors that may speed up cataract formation are:
Family history of cataracts
Long-term use of corticosteroids
(taken by mouth) or certain other medications
Surgery for another eye problem
Too much exposure to ultraviolet
In many cases, the cause of cataract is unknown.
Adult cataracts develop slowly and painlessly. Vision in the affected eye or
eyes slowly gets worse.
Mild clouding of the lens often occurs after age 60, but it may not cause
any vision problems.
By age 75, most people have cataracts that affect their vision.
Visual problems may include the following changes:
Being sensitive to glare
Cloudy, fuzzy, foggy, or filmy vision
Difficulty seeing at night or in dim light
Loss of color intensity
Problems seeing shapes against a background or the difference between shades
Seeing halos around lights
Cataracts generally lead to decreased vision, even in daylight. Most people
with cataracts have similar changes in both eyes, although one eye may be
worse than the other. Many people with this condition have only mild vision
Other symptoms may include:
Frequent changes in eyeglass prescription
Signs and tests
A standard eye exam and slit-lamp examination are used to diagnose
cataracts. Other diagnostic tests are rarely needed, except to rule out
other possible causes of poor vision.
The following may help people who have an early cataract:
As vision gets worse, you may need to make changes around the home to avoid
falls and injuries.
The only treatment for a cataract is surgery to remove it. Surgery is done
if you cannot perform normal activities, such as driving, reading, or
looking at computer or video screens, even with glasses.
If a cataract is not bothersome, surgery is usually not necessary. Cataracts
usually do not harm your eye, so you can have surgery when it is convenient
However, some people may have additional eye problems, such as diabetic
retinopathy, that cannot be treated without first having cataract surgery.
For information on surgery, see: Cataract surgery
Vision may not improve to 20/20 after cataract surgery if other eye
diseases, such as macular degeneration, are present. Ophthalmologists can
usually, but not always, determine this in advance.
Early diagnosis and treatment are key to preventing permanent vision
Although rare, a cataract that goes on to an advanced stage (called a
hypermature cataract) can begin to leak into other parts of the eye. This
may cause a painful form of glaucoma and inflammation inside the eye.
Calling your health care provider
Call for an appointment with your health care provider if you have:
Decreased night vision
Problems with glare
The best prevention involves controlling diseases that increase the risk of
a cataract, and avoiding exposure to factors known to promote cataract
Wearing sunglasses when you are outside during the day can reduce the amount
of ultraviolet (UV) light your eyes are exposed to. Some sunglasses do not
filter out the harmful UV. An optician should be able to tell you which
sunglasses filter out the most UV. For patients who smoke cigarettes,
quitting will decrease the risk of cataracts.
Zigler JS Jr, Datiles MB III. Pathogenesis of cataracts. In: Tasman W,
Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott
Williams & Wilkins; 2011:chap 72B.
Howes FW. Indications for lens surgery/indications for application of
different lens surgery techniques. In: Yanoff M, Duker JS, eds.
Ophthalmology. 3rd ed. St. Louis, Mo: Mosby Elsevier; 2008:chap 5.4.