What is Macular Degeneration?
Age-related macular degeneration (AMD) is a disease that affects your central vision. It is a common cause of vision loss among people over age of 60. Because only the center of your vision is usually affected, people do not go totally blind from macular degeneration. However, AMD can sometimes make it difficult to read, drive, or perform other daily activities that require fine, central vision.
What is the Macula?
The macula is in the center of the retina, the light-sensitive layer of tissue at the back of the eye. As you read, light is focused onto your macula. Where millions of photoreceptors change the light into nerve signals that tell the brain what you are seeing. This is called your central vision. Your central vision allows you to read, drive, and perform other activities that require fine, sharp, straight-ahead vision.
How Does AMD Damage Vision?
AMD occurs in two forms:
Dry AMD affects about 90 percent of those with the disease. Its cause is unknown. Slowly, the light sensitive cells in the macula break down. With less of the macula working, as the years go by, you may start to lose central vision in the affected eye. Dry AMD often occurs in just one eye at first. You may get the disease later in the other eye. We have no way of knowing if or when both eyes may be affected.
Wet AMD -- Although only 10 percent of all people with AMD have this type, it accounts for 90 percent of all severe vision loss from the disease. It occurs when new blood vessels under the retina start to grow toward the macula. Because these new blood vessels tend to be very fragile, they will often leak blood and fluid under the macula. This causes rapid damage and scarring to the macula that can lead to the loss of central vision in a short period of time.
Who is at Risk For AMD
Although AMD can occur during middle age, the risk increases as a person gets older. Results of a large study showed that people in their 50s have about a two percent chance of getting AMD. This risk rises to nearly 30 percent in those over age 75. Besides age, other AMD risk factors include:
Gender -- Women may be at greater risk than men, according to some studies.
Smoking -- Smoking may increase the risk of AMD.
Family History -- People with a family history of AMD may be at higher risk of getting the disease.
Cholesterol -- People with elevated levels of blood cholesterol may be at higher risk for wet AMD.
What are the Symptoms of AMD
Neither dry nor wet AMD causes any pain. The most common symptom of dry AMD is slightly blurred vision. You may need more light for reading or other tasks. Also, you may find it hard to recognize faces until you are very close to them.
As dry AMD gets worse, you may see a blurred spot in the center of your vision. This spot occurs because a group of cells (photoreceptors) in the macula have stopped working properly. Over time, the blurred spot may get bigger and darker, taking more of your central vision.
People with dry AMD in one eye often do not notice any changes in their vision. With one eye seeing clearly, they can still drive, read, and see fine details. Some people may notice changes in their vision only if AMD affects both of their eyes.
An early symptom of wet AMD is that straight lines appear wavy. This happens because the newly formed blood vessels leak fluid under the macula. The fluid raises the macula and distorts your vision. Another sign that you may have wet AMD is rapid loss of your central vision. This is different from dry AMD in which loss of central vision occurs slowly. As in dry AMD, you may also notice a blind spot.
The picture on the left shows how a normal person would view the scene. The photos in the middle and to the left simulate how a person affected with macular degeneration might view the scene. If you notice any of these changes in your vision, call us at once for an eye exam.
How is AMD Detected
We detect AMD during an eye examination that includes:
Visual acuity: The eye chart test measures how well you see at various distances.
Pupil dilation: This examination enables us to see more of the retina and look for signs of AMD. To do this, drops are placed into your eye to dilate (widen) the pupil. After the examination, your vision may remain blurred and you may be sensitive to bright light for several hours.
One of the most common early signs of AMD is the presence of drusen. Drusen are tiny yellow deposits in the retina. We can see them during an eye examination. The presence of drusen alone does not indicate a disease, but it might mean that the eye is at risk for developing more severe AMD.
While conducting the examination, we may ask you to look at an Amsler grid. This grid is a pattern that resembles a checkerboard. You will be asked to cover one eye and stare at a black dot in the center of the grid. While staring at the dot, you may notice that the straight lines in the pattern appear wavy or missing. These may be signs of wet AMD (See Amsler Grid below.)
If we suspect you have wet AMD, you may need to have a test called fluorescein angiography. In this test, a special dye is injected into a vein in your arm. Pictures are then taken as the dye passes through the blood vessels in the retina. The photos help us evaluate leaking blood vessels to determine whether they can be treated.
On the left is what an Amsler grid normally looks like, and the illustration on the right demonstrates metamorphopsia or distorted vision. These grids are reduced in size; we will provide you a full-size grid, with instructions, to use at home.
A person with metamorphopsia would see something like the photos below.
How is AMD Treated
Dry AMD currently cannot be treated. This does not mean that you will lose your sight. Fortunately, dry AMD develops very slowly. You may lose some of your central vision over the years, however, most people are able to lead normal, active lives -- especially if AMD affects only one eye.
Some cases of wet AMD can be treated with laser surgery. The treatment involves aiming a high-energy beam of light directly onto the leaking blood vessels. Laser treatment is more effective if the leaky blood vessels have developed away from the fovea -- the central part of the macula. Even if the blood vessels are growing right behind the fovea, the treatment can be of some value in stopping further vision loss. If the vessels continue to leak, you might need some more laser surgery. It is important to realize that laser surgery is not a cure for AMD. It is only a treatment to help stop further vision loss. There is a relatively high risk of new blood vessels growing back after laser treatment. In some cases wet AMD may be treated by a relatively new technique that involves a medication that is administered via injection and is then activated by shining a laser in the back of your eyes.
What Research is Being Done
The National Eye Institute (NEI) is the Federal government's lead agency for vision research. The NEI is supporting a number of research studies both in the laboratory and with patients to learn more about the cause of AMD. This research should provide better ways to detect, treat, and prevent vision loss in people with the disease.
Findings from the NEI-sponsored Age-related Eye Disease Study (AREDS) showed that high levels of antioxidants and zinc significantly reduced the risk of advanced age-related macular degeneration (AMD) by about 25 percent.
Scientists have begun to study the possibility of transplanting healthy cells into a diseased retina. Although this work is at a very early stage and still experimental, someday it may help people keep their vision or restore some lost vision.
What Can You Do to Protect Your Vision
If you have dry AMD, we should examine your eyes through dilated pupils at least once a year. This will allow us to monitor your condition and check for other eye diseases as well.
We will also provide you an Amsler grid, with instructions, for use at home. This will provide you with a quick and inexpensive test to evaluate your vision each day for signs of wet AMD. You also may want to check your vision by reading the newspaper, watching television, and just looking at people's faces. If you detect any changes, you should call us immediately.
If you have wet AMD, it is important not to delay laser surgery if surgery is recommended. After surgery, you will need to have frequent eye examinations to detect any recurrence of leaking blood vessels. Studies have shown that people who smoke have a greater risk of recurrence of leaking blood vessels than those who don't smoke.
In addition, you should continue to check your vision (at home with the Amsler grid or other methods) as described under dry AMD and schedule an eye exam immediately if you detect any changes.
In the past few years the anti-VEGF (Vascular Endothelial Growth Factor) medications have been found to be the most successful treatment for wet macular degeneration. The two anti-VEGF medications approved for use in the United States are Macugen and Lucentis.
What Can You Do if You Have Already Lost Vision to AMD
Normal use of your eyes will not cause further damage to your vision. Even if you have lost sight to AMD, you should not be afraid to use your eyes for reading, watching TV, and other activities.
Low vision aids are available to help you make the most of your remaining vision. Low vision aids are special lenses or electronic systems that make images appear larger.
If you are finding that your vision loss is having a detrimental impact on your ability to complete everyday tasks please let us know and we can discuss what options are available to make these tasks easier. In addition, groups and agencies that offer information about counseling, training, and other special services are available. Please let us know if you need help in locating any of these resources.
This document was updated 07/20/2009.
Portions of this document were adapted, with permission, from the National Eye Institute document Facts about Macular Degeneration.