This information was developed by the National Eye Institute to help
patients and their families search for general information about
cataracts. An eye care professional who has examined the patient's eyes
and is familiar with his or her medical history is the best person to
answer specific questions.
Cataract Defined
What is a cataract?
A cataract is a clouding of the lens in the eye that affects vision.
Most cataracts are related to aging. Cataracts are very common in older
people. By age 80, more than half of all Americans either have a
cataract or have had cataract surgery.
A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
What is the lens?
The lens is a clear part of the eye that helps to focus light, or an
image, on the retina. The retina is the light-sensitive tissue at the
back of the eye.
In a normal eye, light passes through the transparent lens to the
retina. Once it reaches the retina, light is changed into nerve signals
that are sent to the brain.
The lens must be clear for the retina to receive a sharp image. If
the lens is cloudy from a cataract, the image you see will be blurred.