Eye Disorders

What is Age-Related Macular Degeneration?

Age-related macular degeneration (AMD) is the most common cause of vision impairment in the United States and other western countries. The disease is called age-related macular degeneration because a person's risk of losing vision increases with age. Nearly one-third of people over the age of 75 years have some eye changes due to AMD, and about 7% have the advanced form in which vision is affected. It is estimated that approximately 1.7 million people in the United States have vision impairment from AMD.

People who develop AMD develop disturbance of central vision. Among the symptoms most commonly experienced are a central blurred or blank spot, distortion of objects, or simply blurred vision.

Age-related macular degeneration causes damage to the light-sensitive layer in the back of the eye called the retina. The tiny central region of the retina is known as the macula. No larger than a pencil point, it is responsible for the sharp straight-ahead vision that allows us to read, drive, and distinguish faces.

In the early stage of age-related macular degeneration, yellow fat-containing deposits called drusen form in the macula. These deposits are quite common in the normal population over 40 years of age, but become larger and more numerous in those eyes that will develop AMD.

Two forms of age-related macular degeneration are generally recognized. In "dry" AMD, the most common form, the retina, its pigmented cells, and the adjacent blood vessel layer gradually become damaged (over months and years), usually resulting in mild, slowly progressive vision impairment. In "wet" AMD, vision loss is more rapid (usually over days, weeks, or months) and severe, and is characterized by newly formed blood vessels growing under the retina. These unwanted vessels, termed choroidal neovascularization, leak, bleed, form scar tissue, and commonly lead to severe loss of central vision.

While age-related macular degeneration can result in loss of central vision and legal blindness, it does not cause total loss of vision, even in the most advanced cases. People with AMD may lose the ability to read, drive, and distinguish fine details, but they will retain their ability to perform most other activities and maintain their independence. Magnifiers and other special optical devices can be very helpful in allowing individuals with advanced AMD to maximize their visual potential.

The cause of Age-Related Macular Degeneration is not known. Heredity plays a role, and certain environmental factors, such as cigarette smoking, have been shown to be risk factors for the disease. Other potential influences include nutrition and light exposure, although conclusive evidence does not yet exist.

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