A cataract is a loss of transparency in the normally clear lens of the eye. At first, a small, hazy spot may appear in the field of vision. Gradually (often over a period of years), as the lens grows more opaque, vision becomes increasingly blurry, especially at night or in very bright light.

About 75 percent of Americans over age 60 show some signs of cataracts. Advanced cases are easily treated with surgery (although most patients can postpone surgery for years).

Symptoms of Cataracts

• Gradual, painless, increasingly blurred or double vision.

• Halos or blurriness around lights. Vision may actually be better in dim light, since bright light causes the pupil to constrict and increases the passage of light through the part of the lens most affected by a cataract.

• Increased sensitivity to light and glare.

• Dulled color perception.

• Temporary improvement in near vision (patient may no longer need reading glasses for a brief period).

• Frequent changes in eyeglass or contact lens prescriptions.

• Difficulty driving at night or in bright light.

• Yellowish or milky white appearance of the lens in advanced cases.

What Causes Cataracts?

• Aging is the single greatest risk factor for cataracts, as cumulative exposure to the sun’s ultraviolet rays over a lifetime appears to be a primary cause.

• Exposure to radiation, including x-rays and microwaves, may promote cataracts.

• Physical injury to or inflammation of the eye (for example, uveitis or iritis) may lead to cataracts.

• The long-term use of corticosteroid drugs, hereditary factors, and birth defects may be contributing factors.

• Cataracts may occur at a younger age in people with diabetes mellitus.

Prevention of Cataracts

• Wear sunglasses marked “general purpose” or “special purpose,” or those that indicate they block at least 95 percent of ultraviolet-B (UVB) rays.

Diagnosis of Cataracts

• Eye examination by an ophthalmologist.

How To Treat Cataracts

• To minimize glare outdoors, wear a wide-brimmed hat and sunglasses.

• Indoors, use floor or desk lamps with incandescent bulbs instead of ceiling or fluorescent lights. Avoid pinpoint halogen lights, which cause the pupils to constrict. Installing dimmer controls is advised.

• When reading, try large-print books and newspapers.

• Surgery (successful in 95 percent of cases) is the only cure for cataracts. It can often be postponed indefinitely but is advised when cataracts interfere with normal activities. During the operation the lens is removed and replaced with a plastic intraocular lens implant. (Special contact lenses or eyeglasses may be used when an implant is ruled out.)

When To Call A Doctor

• See an ophthalmologist for any vision problems.

For more information on cataracts and related vision and eye care disorders, click on this link -- Johns Hopkins Health Alerts: Vision and Eye Care

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