A cataract is a clouding of the lens of the eye that results in obscured vision. People with this defect see their environment as if they were looking through a waterfall. Normally, the lens is clear. Its function is to focus light onto the light-sensitive cells lining the back of the eye, so that objects at various distances can be seen clearly. If the lens becomes hazy, however, incoming light is scattered and vision blurs.

Causes

The exact cause of cataracts is unknown. Aging may play a role, but the condition also occurs in some newborns whose mothers contracted German measles during pregnancy.

Diabetes, glaucoma, and detachment of the retina (the innermost layer of the eye) may lead to cataracts. Injury to the lens, prolonged use of certain drugs (including steroidal drugs such as prednisone), and high doses of radiation (for example, from prolonged exposure to X-rays) may also trigger the condition.

Although the condition is usually curable, cataracts can cause blindness. In addition, the shadowy lens prohibits a clear view of the interior of the eye. Because of this obstruction, a physician may not be able to detect other potentially serious eye disorders, such as changes in the retina and damage to the optic nerve (which transmits information from the eye to the brain).

Symptoms

The main symptom of cataracts is painless blurring of vision, occurring most often in only one eye. During the initial stages of development, cataracts can cause the person to experience glare in bright light, since the clouded lens scatters, rather than focuses, incoming light. As the condition progresses, the lens becomes milky white, and vision continues to worsen.

Treatment

Successful treatment begins with surgical removal of the affected lens. With the aid of a microscope, the surgeon opens an area in the front of the eye and removes the lens. The use of local anesthetic eyedrops makes this usually outpatient procedure relatively painless.

After the patient has recuperated for a few weeks, special cataract eyeglasses or a contact lens can be prescribed to help correct the vision. These aids are by no means perfect and require an adjustment period.

Another option, one that most doctors now recommend, is the implantation of an intraocular lens in the eye after cataract surgery. The lightweight plastic lens is relatively free of distortion. It affords vision that is closer to normal than cataract eyeglasses or contact lenses can provide, because it occupies the exact position of the natural lens. (Eyeglasses may still be necessary, however.)

In the vast majority of cases, surgery for cataracts is without complications. Restoration or substantial improvement of vision usually results after surgery. If vision remains unimproved, a disorder that was not detected due to the presence of the cataract may be the cause.