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How does AMD
damage vision? |
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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.
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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, you may start to lose central vision in the affected eye as the years go by. Dry AMD often occurs in just one eye at first. You may get the disease later in the other eye. Doctors have no way of knowing if or when both eyes may be affected. |
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Wet AMD—Although only 10 percent of all
people with AMD have this type, it accounts for 90 percent of all
blindness from the disease. It occurs when new blood vessels behind 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 to the macula that can lead to the loss
of central vision in a short period of time.
Although AMD can occur during middle age,
the risk increases as a person gets older. Results of a large study show
that people in their 50s have about a 2 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. 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 and 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 in the macula have stopped working.
Over time, the blurred spot may get bigger and denser, 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. |
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 The same scene as it might be viewed by a person with AMD. |
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Eye care professionals detect AMD during
an eye examination that includes: One of the most common early signs of AMD is the presence of drusen.
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, your eye care professional 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
to you. This may be a sign of wet AMD. (See Amsler Grid below.) 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 your eye care professional evaluate leaking blood vessels to determine whether they can be treated. Vitamins and minerals. Many researchers and eyecare practitioners believe that antioxidant vitamins, such as beta-carotene (vitamin A) and vitamins C and E, may protect the macula from damage. In fact, a recently published study of over 3600 people found that supplementation with vitamins C and E, beta-carotene and zinc reduced certain patients' risk of progressing to advanced AMD by about 28%. This number reflects those patients with a lot of intermediate or large drusen, but not those with limited intermediate drusen or multiple small drusen. Because of their findings, the researchers recommend that patients at risk of developing advanced AMD consider taking antioxidant and zinc supplements. Participants received:
Bausch & Lomb is now marketing these nutrients in one supplement, called Ocuvite PreserVision. Note that smokers should avoid beta carotene supplements, as they increase the risk of lung cancer in smokers and those who've recently quit.* The eyecare community does not agree on the benefits of zinc or antioxidant supplements: more study is needed, especially on the long-term effects of high-dose supplementation. Keep in mind also that too much of any vitamin or mineral may affect the body's ability to absorb other important nutrients. Visudyne drug treatment. For those with wet AMD, the Food and Drug Administration has recently approved Visudyne, the first-ever drug therapy for this form of the disease. It's only for those whose new blood vessels are characterized as "predominantly classic": about 40% to 60% of new wet AMD patients, according to Visudyne maker CIBA Vision. In this treatment procedure, the doctor injects Visudyne into your arm, then activates the drug by shining a laser into your eye. In clinical trials, 67% of patients found that either their vision loss stabilized or that their vision improved.
How is laser surgery
performed? Laser treatment. Laser photocoagulation may help wet AMD patients by destroying new blood vessels to prevent leakage. Scientists are currently studying laser treatments for dry AMD as well. Low vision devices for vision loss. Although much progress has been made recently in ARMD treatment research, as things stand now, any central vision lost to dry AMD will probably not be restored. Your eyecare practitioner may ask you to check your vision with an Amsler grid, a piece of paper with a black grid of lines. Viewing the Amsler grid separately with each eye helps you monitor your vision loss. For those who have suffered vision loss, many low vision devices are available to help improve vision by using magnifying lenses and bright lights. Some low vision aids shift images to the periphery for clearer vision. |
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Because
only the center of your vision is usually affected, people rarely go
blind from the disease. However, AMD can sometimes make it difficult to
read, drive, or perform other daily activities that require fine,
central vision. 
Drusen
are tiny yellow deposits in the retina. Your eye care professional can
see them during an eye examination.
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