Age-Related Macular Degeneration

Age-related macular degeneration is deterioration of the macula, the central and most sensitive area of the retina.

Macular degeneration is the most common cause of irreversible central vision loss among older people. In its early stage, macular degeneration usually does not cause any symptoms. In advanced stages, macular degeneration can lead to distortion of vision, vision loss, and central blind spots.

Macular degeneration is categorized into two types: dry (non-neovascular) and wet (neovascular). In dry macular degeneration, the more common of the two types, the light-sensitive cells of the macula may be lost, and the retina thins (atrophies). In wet macular degeneration, abnormal blood vessels develop beneath the macula. These vessels leak fluid and blood, which results in the formation of scar tissue. Scar tissue can impair vision by causing light-sensitive cells to die. The dry type usually is present in both eyes, whereas the wet type most often affects one eye at a time. Only a few people with dry macular degeneration eventually develop wet macular degeneration. However, once wet macular degeneration develops in one eye, there is a 50% chance that it will develop in the other eye within 5 years. People who smoke or who have high blood pressure may be at higher risk of progression to the wet type.

Causes

The exact cause of age-related macular degeneration is unknown. In general, the disease occurs only in older people. It is also more common among whites, people with a family history of the disease, past or present smokers, and people with low dietary intake of antioxidants. Age-related macular degeneration may also be more common among women, people with fair skin, and people with light-colored eyes.

Symptoms

Most people with the dry type of the disease have no symptoms, although some people experience mild distortion in their vision. Painless progressive loss of central vision and development of a central blind spot can occur with advanced dry macular degeneration as the retina thins (atrophies). In contrast, people with the wet type often experience an abrupt deterioration and distortion of vision over days or weeks.

People who experience distortion in their central vision or the gradual appearance of a blind spot in one eye, either from advanced dry macular degeneration or wet macular degeneration, have difficulty reading, driving, seeing faces, and watching television. Objects may appear washed out, and the ability to distinguish fine detail or to see in the dark may be lost. People retain their peripheral vision, which allows them to perform daily tasks (other than driving and reading) and remain independent. Total blindness is rare, but if both eyes are affected, blindness may result.

Diagnosis

An eye doctor diagnoses macular degeneration by examining the back of the eye after dilating the pupils. Fluorescein angiography—a test in which a dye is injected into an arm vein and photographs are taken of the retina—may be necessary to determine whether new blood vessels are forming. The test can also help the doctor assess whether treatment will benefit a person with the wet type of the disease.

Treatment

Some people with certain forms of dry macular degeneration can slow the rate of further vision loss by taking high-dose supplements of vitamin C, vitamin E, beta-carotene, zinc, and copper. A doctor can inform the person as to whether he has one of the forms that might be helped by vitamin supplements.

People with wet macular degeneration may be candidates for a special type of laser therapy (thermal laser photocoagulation) or photodynamic therapy. Photodynamic therapy has been shown to be effective for people with wet macular degeneration that has certain features. These features can be identified only by fluorescein angiography and a physical examination. Laser and photodynamic therapy either destroy abnormal blood vessels or limit their growth and thereby reduce the likelihood of further vision loss and the rate of progression of any additional loss that does occur.

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