What are the signs and symptoms of AMD?
What can be done to prevent or limit AMD?
What treatment is available for AMD?
Where can I get more information about AMD?
What
is AMD?
Age-related macular degeneration is a common, serious disease
of the eye’s retina. This condition is associated with aging
and gradually destroys the sharp, central vision that is needed for
seeing objects clearly and for common daily tasks such as reading and
driving. The disease progresses faster in some people than in others
and may lead to a loss of vision in one or both eyes. AMD is the leading
cause of legal blindness in America. It is estimated that about 13 million
people in this country have some form of AMD - over 1.6 million of them
afflicted with the late, vision-destroying stages of the disease.
The retina is the paper-thin tissue that lines the back of the eye and sends visual signals to the brain. In the center of the retina is a small area (about a fifth of an inch in diameter) called the macula. It is made up of millions of closely packed, light-sensing cells that produce your central vision. In AMD there is a slow breakdown of the cells in and behind the macula, accompanied by a gradual loss of central vision. In many people AMD does not progress beyond its early stages (some changes in how the retina appears to an eye care professional).
Late-stage AMD occurs in two forms—dry (or atrophic) and wet (or exudative). Ninety percent of all people with late AMD have the dry type; its basic cause is not yet known and is a topic of much scientific investigation. The wet form, although only 10 percent of all people with late AMD have it, accounts for 90 percent of legal blindness from the disease. As AMD worsens, new blood vessels may begin to grow. Because these new vessels tend to be very fragile, they will often leak blood and fluid under the macula, resulting in wet AMD. This causes rapid damage to the macula that can lead to the loss of central vision in a short period of time.
Who
is at risk for AMD?
The greatest risk factor is older age; people over age 60 are
at much greater risk than other age groups: although the chance of having
AMD is only one percent at age 55-64, this prevalence rises to four
percent for those over 65, and 30% of the American population over age
75. The US population over 65 is expected to double in the next 30 years,
so AMD will become even more of a problem as the baby-boomer generation
ages.
Because women live, on average, several years longer than men, women are twice as likely as men to develop the condition. The lifetime risk for getting AMD is 6% for females and only 3% for males. Therefore, women need to be more aware of AMD, and older women should be sure to visit an ophthalmologist or optometrist at least every other year.
After increasing age, smoking is the strongest predictor of who will get AMD; this habit can double the risk of the disease. Family history is also important; people whose immediate family members (including grandparents) had AMD are at higher risk of developing the disease. Scientists are trying to find out which genes are responsible for this hereditary component.
What
are the signs and symptoms of AMD?
The early sign of susceptibility to AMD is deposits behind
the retina, which are called drusen. These are visible to the ophthalmologist
or optometrist examining your eyes. Most older people have some small,
“hard” drusen, which are not a cause for concern. However,
large, “soft” drusen (sometimes called ARM, or age-related
maculopathy) are often a sign that the person will progress to symptomatic
AMD. Neither dry nor wet AMD causes any pain.
The most common early symptom of dry AMD is blurred central vision, even when wearing your glasses or contact lenses. When fewer cells in the macula are able to function, patients will see details in front of them, such as faces or words in a book, less clearly. Often this blurry spot will, at first, go away in brighter light. But if the loss of the central, light-sensing cells becomes great, people may see a constant small and growing, dark or empty area in the middle of their field of vision.
The classic early symptom of wet AMD is that straight lines appear curved or distorted. This results when fluid from the leaking blood vessels gathers and lifts the macula, distorting vision. Your eye care professional may suspect AMD if you are over age 60 and have had recent changes in your central vision. To look for signs of the disease, he or she will use eye drops to dilate, or enlarge, your pupils, allowing the doctor to view the back of the eye clearly. You may also be asked to view an Amsler grid, a pattern that looks like a checkerboard. Early changes in your central vision will cause the grid to appear distorted, a sign of AMD.
As the loss of central vision progresses, the decrease in ability to drive, read, and see faces can result in loss of independence. Because of poor eyesight, there is an increased risk of falling, which can result in hip fracture, especially in women (because osteoporosis is much more common in women than in men).
What
can be done to help prevent or limit AMD?
There is no way to prevent getting older or to change your
genes. However, you can protect yourself in other ways. Most important,
this is one more reason to stop smoking.
There is strong evidence that a diet rich in fruits and dark green vegetable lowers the risk of AMD. However, it is not yet clear which of the many compounds in food are important for prevention, so the best advice is to eat healthily. The carotenoids, lutein and zeaxanthin, may be two of the protective compounds. A new study showed that supplementing your diet with an antioxidant combination (vitamins C and E, beta-carotene, and zinc with copper) may retard the progression in some people who already have moderate AMD; however, these food supplements appear to have no effect in preventing the disease in otherwise healthy individuals.
Bright light may be involved in the process that starts AMD, so it is prudent for you and your children to wear hats and sunglasses to protect your eyes in bright sunlight.
Because of the genetic component to AMD, if a close relative had the disease there is more reason to monitor your vision closely and to have frequent eye examinations.
It is recommended that everyone over age 60 should be examined at least every two years by an ophthalmologist or optometrist. One reason is to detect AMD early, as there is no pain or other symptoms in early stages. In this way, the disease can be followed and arrested before a disastrous retinal hemorrhage occurs. In addition, it is very important to detect another eye disease striking older people—glaucoma—early and to begin treatment for it before there is damage to the optic nerve; if glaucoma is left untreated, blindness is likely.
If you already have wet AMD in one eye, this disease usually will eventually affect the other. You need to see your eye care professional often and check an Amsler grid at home.
What
treatment is available for AMD?
Unfortunately, no effective treatment now exists for the dry
form of AMD. However, it is crucial that patients who progress to wet
AMD and need treatment have it done before the disease destroys their
central vision. For this reason, if you have early AMD you should have
your eyes examined through dilated pupils at least once a year.
Laser therapies to seal off leaking blood vessels can help reduce the
risk of advancing vision loss in most wet AMD cases. This treatment
involves aiming a strong light beam onto the new blood vessels to destroy
them. Photodynamic therapy (PDT) is a recent improvement in laser surgery
that causes much less damage to the retina: A drug (usually Visudyne)
is injected into the patient’s arm and travels through the bloodstream
to the abnormal vessels in eye. The laser beam is then aimed at these
vessels to activate the drug, which works to stop or slow the blood
leakage. Several repeated treatments are usually required, and the disease
process is just slowed, not stopped. Any lost vision cannot be restored.
A promising new treatement for wet AMD uses antibodies to inhibit a
growth factor (VEGF) that is largely responsible for forming the new
blood vessels. This treatment is very successful at slowing the progression
of the vessels, and actually improves the vision of the average patient
(the only method to do so). The drugs (either Lucentis or Avastin) need
to be injected monthly directly into the vitreous jelly of the ailing
eye. However, the rate of serious complications is very low.
Research in molecular biology, genetics, and epidemiology is showing
that inflammatory processes may trigger AMD; learning more about this
aspect of the disease may lead to novel treatments in the future.
If you already been diagnosed with AMD (even in a very early stage)
and you are covered by Medicare, it will pay for future visits to your
eye care doctor.
Many people with central-vision loss retain very usable peripheral (side)
vision. This can be used to good advantage with low-vision aids, such
as video magnifiers, which are available for patients even after medical
treatment is no longer possible. These devices can be customized for
each patient, and usually are very helpful for reading and for watching
TV. Some AMD patients are even able to drive safely again when fitted
with special, small telescopes which are mounted on eye glasses.
Where
can I get more information about AMD?
The National
Eye Institute (NEI ), a branch of the National Institutes of Health,
has lots of reliable, easily understood information available on its
web site. For example, you can see what the world looks like to AMD
patients, try out an Amsler grid, and learn how to obtain low-vision
aids and advice. Or, find out if free
or low-cost eye screenings by eye care professionals are available
to qualifying individuals in your area.
All of the NEI information is available, free, by writing to: National Eye Health Education Program, 2020 Vision Place, Bethesda, MD 20892-3655.
Both Schepens Eye Research Institute and Prevent Blindness America have fact sheets available on AMD and other eye problems.
More sources of information are: Macular Degeneration International and the American Macular Degeneration Foundation.
