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The Merck Manual--Second Home Edition logo
 
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Chapter 234. Retinal Disorders
Topics: Introduction | Age-Related Macular Degeneration | Macular Pucker | Retinal Detachment | Retinitis Pigmentosa | Blockage of Central Retinal Arteries and Veins | Hypertensive Retinopathy | Diabetic Retinopathy | Endophthalmitis | Cancers Affecting the Retina
 
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Age-Related Macular Degeneration

Age-related macular degeneration (age-related maculopathy) causes progressive damage to the macula, the central and most vital area of the retina, resulting in gradual loss of vision.

Age-related macular degeneration affects older people and is equally common in men and women; it is more common in fair-skinned people and in those who smoke. The cause is unknown, but the condition tends to run in families.

There are two forms of age-related macular degeneration, dry (atrophic) and wet (neovascular or exudative) macular degeneration. In dry macular degeneration, the tissues of the macula thin as cells disappear. There is no evidence of scarring or of bleeding or other fluid leakage in the retina. In wet macular degeneration, abnormal blood vessels develop in the layer of tissue under the macula. These vessels may leak fluid and blood under the retina in that area. Eventually a mound of scar tissue develops under the retina. Macular degeneration is a slow process. Both eyes may be affected simultaneously in the dry form. The wet form develops in one eye first but eventually affects both eyes.

Symptoms and Diagnosis

In dry macular degeneration, central vision slowly and painlessly worsens. Objects may appear washed out, or fine detail may be lost. Sometimes a doctor can see early physical changes near the macula, even before symptoms develop. In wet macular degeneration, loss of vision tends to progress quickly and may be particularly sudden if one of the abnormal blood vessels bleeds. The first symptom may be distortion of vision in one eye, so that fine, straight lines appear wavy. Often, difficulty with reading or watching television results.

Macular degeneration can severely damage vision, but it rarely leads to complete blindness. Vision at the outer edges of the visual field (peripheral vision) and the ability to see color are generally not affected. The dry type tends to result in less sudden or severe vision loss and generally develops more slowly than the wet type.

A doctor can usually diagnose macular degeneration by examining the eyes with an ophthalmoscope or a slit lamp. Sometimes fluorescein angiography--a procedure in which a doctor injects dye into a vein and photographs the retina--is used to determine the diagnosis.

Treatment

No treatment is currently available for the dry type. No treatment is currently recommended for mild or severe disease. People with moderate disease may benefit from high doses of antioxidants (vitamin C, vitamin E, and beta-carotene) and zinc and copper. Transplantation of retinal tissue is being studied and may eventually be available.

In the wet type, when new blood vessels grow in or around the macula, a laser can be used to destroy them before they do further harm. If the laser is used to destroy retinal and choroidal tissue as well, this treatment is called thermal laser. Another promising treatment is photodynamic therapy. In this treatment, a substance that sensitizes the blood vessels in the eye to laser light is given intravenously, and then a beam of laser light is used to destroy these abnormal blood vessels. Transpupillary thermotherapy is an alternative treatment, in which an infrared laser is used. Both photodynamic therapy and transpupillary thermotherapy are used to damage the new blood vessels without damaging the retina or choroid.

Magnifiers, reading glasses, telescopes, and closed-circuit television magnifying devices may help people with poor vision. There are also a variety of low-vision aids for computer users. For instance, one device projects an enhanced image from the computer onto an undamaged part of the retina. Software is available that displays computer data in large print or reads the data aloud in a synthetic voice. Counseling regarding the types of services that are available for people with poor vision is advisable and is typically given by a low-vision specialist (an ophthalmologist or optometrist who specializes in treating those with very poor vision).

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