A cataract is a clouding of the eye's lens that can cause vision problems.
The most common type is related to aging. More than half of all Americans
age 65 and older have a cataract.
In the early stages, stronger lighting and eyeglasses
may lessen vision problems caused by cataracts. At a certain point, however,
surgery may be needed to improve vision. Today, cataract surgery is safe
and very effective.
The lens is the part of the eye that helps
focus light on the retina. The retina is the eye's light-sensitive
layer that sends visual signals to the brain. In a normal eye, light passes
through the lens and gets focused on the retina. To help produce a sharp
image, the lens must remain clear.
The lens is made mostly of water and protein. The
protein is arranged to let light pass through and focus on the retina.
Sometimes some of the protein clumps together. This can start to cloud
small areas of the lens, blocking some light from reaching the retina
and interfering with vision. This is a cataract.
In its early stages, a cataract may not cause a problem.
The cloudiness may affect only a small part of the lens. However, over
time, the cataract may grow larger and cloud more of the lens, making
it harder to see. Because less light reaches the retina, your vision may
become dull and blurry. A cataract won't spread from one eye to the other,
although many people develop cataracts in both eyes.
Although researchers are learning more about cataracts,
no one knows for sure what causes them. Scientists think there may be
several causes, including smoking, diabetes, and excessive exposure to
The most common symptoms of a cataract are:
These symptoms can also be a sign of other eye problems.
If you have any of these symptoms, check with your eye care professional.
- Cloudy or blurry vision.
- Problems with light. These can include headlights
that seem too bright at night; glare from lamps or very bright sunlight;
or a halo around lights.
- Colors that seem faded.
- Poor night vision.
- Double or multiple vision (this symptom often goes
away as the cataract grows).
- Frequent changes in your eyeglasses or contact
When a cataract is small, you may not notice any
changes in your vision. Cataracts tend to grow slowly, so vision gets
worse gradually. Some people with a cataract find that their close-up
vision suddenly improves, but this is temporary. Vision is likely to get
worse again as the cataract grows.
- Age-related cataract: Most cataracts are
related to aging.
- Congenital cataract: Some babies are born
with cataracts or develop them in childhood, often in both eyes. These
cataracts may not affect vision. If they do, they may need to be removed.
- Secondary cataract: Cataracts are more likely
to develop in people who have certain other health problems, such as
diabetes. Also, cataracts are sometimes linked to steroid use.
- Traumatic cataract: Cataracts can develop
soon after an eye injury, or years later.
To detect a cataract, an eye care professional examines
the lens. A comprehensive eye examination usually includes:
Your eye care professional may also do other tests to
learn more about the structure and health of your eye.
- Visual acuity test: This eye chart test
measures how well you see at various distances.
- Pupil dilation: The pupil is widened with
eyedrops to allow your eye care professional to see more of the lens
and retina and look for other eye problems.
- Tonometry: This is a standard test to measure
fluid pressure inside the eye. Increased pressure may be a sign of glaucoma.
For an early cataract, vision may improve by
using different eyeglasses, magnifying lenses, or stronger lighting. If
these measures don't help, surgery is the only effective treatment. This
treatment involves removing the cloudy lens and replacing it with a substitute
A cataract needs to be removed only when vision
loss interferes with your everyday activities, such as driving, reading,
or watching TV. You and your eye care professional can make that decision
together. In most cases, waiting until you are ready to have cataract
surgery will not harm your eye. If you decide on surgery, your eye care
professional may refer you to a specialist to remove the cataract. If
you have cataracts in both eyes, the doctor will not remove them both
at the same time. You will need to have each done separately.
Sometimes, a cataract should be removed even if it
doesn't cause problems with your vision. For example, a cataract should
be removed if it prevents examination or treatment of another eye problem,
such as age-related macular degeneration or diabetic
Cataract removal is one of the most common operations
performed in the U.S. today. It is also one of the safest and most effective.
In about 90 percent of cases, people who have cataract surgery have better
There are two primary ways to remove a cataract.
Your doctor can explain the differences and help determine which is best
In most cataract surgeries, the removed lens is replaced
by an intraocular lens (IOL). An IOL is a clear, artificial lens
that requires no care and becomes a permanent part of your eye. With an
IOL, you'll have improved vision because light will be able to pass through
it to the retina. Also, you won't feel or see the new lens.
- Phacoemulsification, or phaco. Your doctor
makes a small incision on the side of the cornea, the clear,
dome-shaped surface that covers the front of the eye. The doctor then
inserts a tiny probe into the eye. This device emits ultrasound waves
that soften and break up the cloudy center of the lens so it can be
removed by suction. Most cataract surgery today is done by phaco, which
is also called small incision cataract surgery.
- Extracapsular surgery. Your doctor makes
a slightly longer incision on the side of the cornea and removes the
hard center of the lens. The remainder of the lens is then removed by
Some people cannot have an IOL. They may have problems
during surgery, or maybe they have another eye disease. For these people,
a soft contact lens may be suggested. For others, glasses that provide
powerful magnification may be better.
Information from National Eye Insititute