Macular degeneration is an eye disorder caused by breakdown of the macula. The macula is the center of the retina at the back of the eye. The images we see are sent to the macula and the rest of the retina. The macula has been compared to the film of a camera because it stimulates the brain so that we "see" the image in our mind.

There are two common types of age-related macular degeneration: the dry or atrophic form and the wet or exudative form. Dry macular degeneration is the most common type. It is caused by the gradual thinning of the macula as a result of aging. A number of small, round sores form under the outer layer of the retina. Over time, these sores multiply and form together, impairing vision.

Wet macular degeneration accounts for only about 10% of cases. It occurs when tiny, abnormal blood vessels form under the retina. These vessels leak fluid or blood, which causes blurring of the central vision. Vision loss may be rapid and severe.

What is going on in the body?

The macula is the most critical portion of the retina. It is responsible for detailed vision. This function is necessary for reading and seeing distant objects in detail. When the macula is damaged, vision is affected. Most of the time, this breakdown is age related. It can also occur in younger people who have a genetic tendency toward the condition.

What are the causes and risks of the condition?

Macular degeneration affects more than 25 million people worldwide. Most of the time, it occurs as part of normal aging. Thirty percent of people over age 75 have macular degeneration.

Risk factors associated with a higher incidence of macular degeneration include the following:

A recent study has identified a gene named ELOVL 4 that is associated with the form of macular degeneration that occurs in adolescents. The gene may also be associated with the age-related form of macular degeneration. More research is needed in this area.