Definition of Macular degeneration - age-related:

Macular degeneration is an eye disorder that slowly destroys sharp, central vision. This makes it difficult to see fine details and read.

The disease is most common in people over age 60, which is why it is often called age-related macular degeneration.

Causes, incidence, and risk factors:

The retina is the inner layer of tissue at the back of the eye. It changes light and images that enter the eye into nerve signals that are sent to the brain. The macula is the part of the retina that makes vision sharper and more detailed.

Macular degeneration is caused by damage to the area around blood vessels that supply the macula. This change in the blood vessels damages the macula.

Two phases of macular degeneration (AMD) exist:

• Dry macular degeneration occurs when the blood vessels under the macula become thin and brittle. Small yellow deposits, called drusen, form. Almost all people with macular degeneration start with the dry form.
• Wet macular degeneration occurs in only about 10% of people with macular degeneration. New abnormal and very fragile blood vessels grow under the macula. This is called choroidal neovascularization. These vessels leak blood and fluid. This form causes most of the vision loss associated with the condition.

Scientists are not sure what causes AMD. The condition is rare before age 55, and is most often seen in adults 75 years or older.

In addition to heredity, other risk factors are:

• Caucasian race
• Cigarette smoking
• High-fat diet
• Female gender
• Obesity