The Sun: Man's Friend & Foe

[Picture of a healthy blue eye] A cataract is a clouding, or opaqueness, of the normally clear lens of your eye. Lens clouding may cause blurred vision, sensitivity to light and glare, fading or yellowing of colors, poor night vision and halos around lights.

How cataracts form isn't known. But long-term exposure to ultraviolet (UV) light, diabetes, a previous eye injury and prolonged use of corticosteroid drugs increase your risk. About half of Americans between ages 65 and 74 and 70 percent of those older than age 75 have cataracts. As a result, it is definitely of some concern to us all.

At birth, your lenses are clear, however with age and chronic exposure to ultraviolet (UV) light, they darken. Darkening causes lenses to absorb progressively more UV light. UV light, which accounts for about 5 percent of sunlight, is not needed to see. The lens filters out damaging UV light and allows other light to pass through to your retina. But while protecting your retina, the lens is slowly self-destructing.

UV light may encourage formation of free radicals. Free radicals are toxic molecules that injure cells in your lens. And since the lens never sheds old cells throughout life, damaged cells accumulate and the lens becomes less transparent.

Though some degree of cataract formation is normal as you grow older, a cataract hampers vision only when located in a portion of the lens that is in line with your pupil. It is only overexposure to UV radiation from sunlight that is now an accepted cause of cataracts.

Normally cataracts are diagnosed with an examination involving tests for visual acuity, side (peripheral) vision, sensitivity to glare, and eye movement. Evaluation usually includes an examination of the internal structures of your eye and a measurement of eye pressure. Your ophthalmologist will evaluate the cataracts density with a slit lamp. A narrow light beam is focused into your eye while your ophthalmologist looks into the area through a special microscope. If the lens is opaque, another procedure uses ultrasound to examine structures behind the lens to exclude other causes of vision problems.

The normal method of treatment involves surgery which restores vision in more than 95 percent of the 1 million cataract operations performed each year in the United States. In the past, people who had cataract surgery wore contact lenses or thick glasses to replace their lenses. Now the most common replacement lens is an artificial lens implanted in your eye during surgery.

Antioxidants such as vitamins C and E and carotenoids can help block some of the damage caused by free radicals. Carotenoids are pigments in fruits and vegetables. Those most often linked to a reduced risk of eye disease occur in dark-green leafy vegetables. Some research also suggests zinc may play a role in protecting against macular degeneration.