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. The National Eye Institute (NEI) estimates that by age 80, more than half of all Americans either have a cataract or have had cataract surgery. Cataracts generally do not cause surface irritation or pain.
A cataract can occur in one or both eyes. It cannot spread from one eye to the other.
Clouded vision can make it more difficult to read, drive a car (especially at night), or to see the expression on another's face. Cataracts commonly affect distance vision and cause problems with glare. The lens is the 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 seen will be blurred.
Clouding of the lens is a normal part of getting older. The Centers for Disease Control (CDC) has found that approximately half of Americans older than 65 have some degree of clouding of the lens. After age 75, as many as 70% of Americans have cataracts that are significant enough to impair vision. Cataracts occur equally in men and women.
Most cataracts develop slowly and do not initially disturb eyesight. Cloudiness occurs over time. As the clouding progresses, the cataract eventually interferes with vision.
In the early stages, stronger lighting and eyeglasses can help the individual deal with the vision problems. But at some point, if impaired vision jeopardizes normal lifestyle, the individual might need surgery. Fortunately, cataract removal is one of the safest, most effective, and most common surgical procedures.

Related Terms

Aftercataracts, choroidal hemorrhage, congenital cataract, cornea, cortical cataract, cystoid macula edema, diabetes, endophthalmitus, extracapsular surgery, glaucoma, hypermature cataract, inflammation, intraocular lens, IOL, ionizing radiation, iris, lens, nuclear cataract, ophthalmoscope, PCO, phacoemulsification, posterior capsule opacification, radiation cataract, retinal detachment, retinitis pigmentosa, sit-lamp examination, subcapsular cataract, traumatic cataract, YAG, yttrium-aluminum-garnet laser.