Macular degeneration is an eye disease that occurs when the small central portion of the retina, known as the macula, is damaged. The retina is the light-sensing nerve tissue at the back of the eye. Because the disease develops as a person ages, it is often referred to as age-related macular degeneration (AMD).
There are two types of age-related AMD, the "dry" form and the "wet" form.
Dry form of AMD
The "dry" form of AMD is characterized by the presence of yellow deposits, called drusen, in the macula. In general, drusen does not cause changes in vision. However, as they grow in size and increase in number, they might lead to a dimming or distortion of vision that people find most noticeable when they read. In more advanced stages of dry AMD, there is also a thinning of the light-sensitive layer of cells in the macula leading to atrophy, or tissue death. In the atrophic form of dry AMD, patients might have blind spots in their vision. In the advanced stages, patients might even lose central vision.
Wet form of AMD
The "wet" form — or exudative neovascular form of AMD — is characterized by the growth of abnormal blood vessels from the choroid underneath the macula. This is called choroidal neovascularization. These blood vessels leak blood and fluid into the eye, causing distortion of vision that makes straight lines look wavy, as well as blind spots and loss of central vision. These abnormal blood vessels eventually scar, leading to permanent loss of central vision.
Most patients with AMD have the dry form of the disease and will not lose central vision. However, the dry form of AMD can lead to the wet form. Although only about 10 percent of people with AMD develop the wet form, they make up the majority of those who experience serious vision loss from the disease.
Because the dry form can change into the wet form, it is very important for people with AMD to monitor their eyesight carefully and see their eye doctors on a regular basis.
Who gets AMD?
As the name suggests, AMD is more common in older adults. In fact, it is the leading cause of severe vision loss in adults over age 60.
AMD might be hereditary, meaning it can be passed on from parents to children. If someone in your family has or had the condition, you might be at higher risk for developing the disease. Talk to your eye doctor about your individual risk.
What are the symptoms?
AMD often does not have symptoms and is unrecognized until it affects both eyes. The first sign of AMD is usually distortion of straight lines. This might progress to a gradual loss of central vision.
Symptoms of AMD include:
- Straight lines start to appear distorted, or the center of vision becomes distorted.
- Dark, blurry areas or white-outs appear in the center of vision.
- Diminished or changed color perception.
If you experience any of these symptoms, see an ophthalmologist as soon as possible.
How is AMD diagnosed?
One of the most common early signs of AMD is the presence of drusen — tiny yellow deposits under the retina. Your doctor can see these during a routine eye exam. Your doctor might also ask you to look at an Amsler grid — a pattern of straight lines that resemble a checkerboard. Some of the straight lines might appear wavy to you, or you might notice that some of the lines are missing. These can be signs of AMD. Sometimes, early AMD can even be detected using a traditional eye chart exam.
If your doctor suspects you have the rare "wet" form, or neovascular form, of AMD, you might have a procedure called fluorescein angiography. During this procedure, a dye — called fluorescein — is injected into the arm. Photographs are taken to show the movement of the dye as it reaches the eye and passes through the blood vessels of the retina. If there are new vessels leaking fluid or blood in the macula, the photographs will show their exact location and their type.
Early detection of AMD is very important because there are treatments that can delay or reduce the severity of the disease.
What treatments are available?
There is currently no cure for AMD, but treatments might prevent severe vision loss and slow the progression of the disease considerably. Several options are available, including:
- Vitamins — Vitamins C, E, beta carotene, zinc, and copper have been shown to decrease the risk of vision loss in patients with intermediate to advanced dry AMD. Ask your eye doctor if these vitamin supplements will benefit you before taking them.
- Laser therapy — High-energy lights are used to destroy actively growing abnormal blood vessels.
- Photodynamic laser therapy — This is a two-step treatment during which a light-sensitive drug is used to damage the abnormal blood vessels. A doctor injects the drug into the bloodstream to be absorbed by the abnormal blood vessels in the eye. The doctor then shines a cold laser into the eye to activate the drug, damaging the abnormal blood vessels.
- Low vision aids — These are devices that have special lenses or electronic systems that produce enlarged images of nearby objects. They help people with partial vision make the most of their remaining vision.
Researchers are studying new treatments for AMD. The following treatments might soon be available, but are currently considered experimental.
- Sub-macular surgery — This is surgery to remove the abnormal blood vessels or blood.
- Retinal translocation — This is a surgical procedure used to destroy abnormal blood vessels that are located directly under the center of the macula, where a laser beam cannot be placed safely. During the procedure, the macular center is rotated away from the abnormal blood vessels to a healthy area of the retina, thus preventing the formation of scar tissue and further damage to the retina. Once moved away from the abnormal blood vessels, a laser is used to treat the abnormal blood vessels.
- Anti-angiogenesis drugs — Several new drugs are being tested to slow down or prevent the growth of the abnormal blood vessels.
What is the outlook for people with AMD?
Unfortunately, AMD can recur even after successful treatment. The various procedures, however, can slow the rate of vision loss and hopefully preserve some sight.
© Copyright 1995-2009 The Cleveland Clinic Foundation. All rights reserved.
Can't find the health information you’re looking for?
Ask a Health Educator, Live!
Know someone who could use this information?...send them this link.
This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/16/2009...#10704
