from Triad's Eye Care Notes
by Triad Publishing Co.
Age-related macular degeneration (AMD) is the leading cause
of poor vision in people over 60. (Some patients are younger,
but that is rare.) When the macula degenerates, central vision
is gradually lost. Peripheral (side) vision normally remains
so AMD does not lead to total blindness. The degeneration
usually involves both eyes, though it may start in one eye
and not affect the other eye until much later.
macula is the tiny area in the retina that provides sharp
central vision. (The retina is the light-sensitive nerve tissue
at the back of the eye: like the film in a camera, it is the
"screen" that images are focused on.) Though the macular area
is no larger than a pinhead, it contains the visual cells
for seeing straight ahead, fine detail, and color. If the
macula is damaged -- or degenerates, as from AMD -- central
vision is interfered with. So when you look at an object,
part of it may seem distorted, blotted out, or shrouded in
a dark haze.
have not yet learned why a macula that has functioned well
for most of your life begins to degenerate. Heredity is likely
to play a role, as well as years of exposure to bright sunlight.
It is also possible that tissue changes accompanying the normal
aging process somehow interfere with the macula's getting
enough oxygen. Smokers and former smokers have been found
to have a much higher risk of AMD, though stopping smoking
does not reverse the degeneration or even slow it down. Other
risk factors are hypertension and heart disease. Some studies
have found a relationship to a high intake of saturated fat,
but those findings are not conclusive.
is not caused by using your eyes too much. People who develop
AMD are typically in good health. The condition does not appear
to be caused by diabetes or by drinking alcoholic beverages.
In fact, drinking a moderate amount of wine has been shown
to decrease the odds of developing AMD.
the normal eye ages, tiny yellowish deposits called "drusen"
sometimes build up under the macula. One form of drusen (called
"hard") may be a normal, harmless sign of getting older, but
"soft" drusen can be a sign that degenerative macular changes
are starting to develop. Yet AMD sometimes develops without
any detectable drusen at all.
are two types: "dry" and "wet." Most patients have the dry
form, which tends to develop slowly as the tissue beneath
the macula gradually deteriorates. With wet AMD, tissue deterioration
is accompanied by tiny abnormal blood vessels called "subretinal
neovascular membranes" that form under the retina. Because
they're fragile they leak fluid or bleed. If the fluid or
blood reaches the macula and lifts it out of position, vision
becomes hazy, distorted, and visual sharpness can be lost.
typical first symptom (with either form) is blurring of vision.
When the blurring is gradual, you may think you need new eyeglasses.
But a new prescription is not likely to improve your vision
because the problem is not with the optical parts of the eye.
time goes on, you may notice a hazy or dark zone in the center
of objects you look at directly. Colors may begin to look
different or lose richness. With wet AMD especially, straight
lines, such as the edges of doorways, may start to look bent
or crooked as vision becomes distorted, and you may see brief
flashes of lights, like a sunburst. Symptoms may be gradual
or sudden -- suddenness is more likely with wet AMD. When
the loss of vision is in one eye only, you can't always tell
how long it has existed, since it is "hidden" when both eyes
are used together. It may only become apparent when the good
eye is covered.
people whose vision has been very poor from AMD (or from other
causes) sometimes have visual hallucinations; they see things
(objects or patterns) that are not really there. These phantom
visions last from a few seconds to a minute or so and then
disappear. Such hallucinations are fairly common and they
are not serious.
vision will be checked and you will have a refraction (test
for glasses) along with a complete eye exam. Your pupils will
be dilated (enlarged) with eyedrops so that the interior of
your eyes can be evaluated with an ophthalmoscope. A special
type of contact lens may be placed on your eyes while your
retinas and maculas are examined under the high magnification
of a slit lamp microscope.
may be taken of the retina at each visit to determine the
extent of the problem and evaluate its progression. If you
have a test called fluorescein angiography, an orange colored
dye called fluorescein will be injected into a vein in your
arm, and then a series of retinal photographs taken as the
dye travels through the eye's blood vessels. The angiogram
(photograph showing blood vessels) helps identify the position
and extent of any abnormal blood vessels or leakages. If more
information is needed, a dye called indocyanine green (ICG)
may be used to make another type of angiogram. Angiograms
provide important guidance for treatment.
far, there are no medications that have proven to be effective.
But wet AMD -- in the early stages only -- can sometimes benefit
from treatment with a surgical laser, to seal the leaks or
destroy the abnormal blood vessels under the macula. (The
laser cannot help the dry type of AMD, or even most stages
of the wet type.)
surgery is never undertaken lightly. No matter how accurately
performed, it involves some risk to vision because the laser
can destroy normal neighboring tissue along with abnormal
tissue. So the procedure will be recommended only if the risk
to your vision is small and there is a reasonable chance for
success -- that means that the degeneration is not too extensive,
too advanced, or too near the center of the macula.
newer type of laser surgery, called photodynamic therapy (PDT),
is sometimes useful. (In several national studies, PDT appeared
to be safer and was proven to be modestly effective for about
two-thirds of those participating.) In this surgery, a light
sensitive dye called verteporphin (Visudyne) is injected into
the arm, travels to the retina, and concentrates in the abnormal
blood vessels. A low intensity red laser is used to activate
the dye. The objective is to destroy the abnormal blood vessels
with the laser without damaging the normal retinal cells in
the area. PDT has been approved by the FDA but further evaluation
is still needed to determine its long term effectiveness.
PDT usually needs to be repeated three to five times over
a year or more. Regular laser surgery may also require several
either standard laser or PDT, a result that is successful
does not always mean that your vision will be better; only
occasionally does vision actually improve. The goal of laser
treatment is to prevent further leakage and stabilize vision.
It is also possible that any beneficial effect will be only
temporary, or there could be an actual worsening. So please
be realistic and don't expect miracles from the laser.
clinical research is ongoing at many centers. Certain antioxidants,
vitamins, and minerals are being studied as a way to slow
the degeneration. Scientific evidence for their effectiveness
is still inconclusive; some studies show beneficial results,
others don't. (Until there are answers, you may decide to
take a regular vitamin-mineral supplement for whatever help
it might offer.)
studies are evaluating the effect of radiation therapy, especially
low-dose x-rays to the eye, to treat the abnormal subretinal
blood vessels. Other studies are aimed at controlling angiogenesis
-- the process by which new blood vessel membranes form under
the retina in wet AMD. The results are not in yet.
new surgical treatments are under investigation: pigment epithelial
transplants, the use of laser burns to "treat" soft macular
drusen, surgery to remove neovascular membranes, and macular
translocation (surgically moving the macula to one side).
All of these are potentially useful treatments but all still
require further evaluation to determine just how effective
they will be.
usually develops gradually or in small spurts over many months,
then slows down or stops. Both eyes will probably be affected,
though one eye may precede the other by a long time, even
years. Wet changes occur unpredictably; they may even develop
in AMD that started as the dry type, or they may recur in
previously treated wet AMD. Even with advanced AMD, most people
do not lose all of their vision.
matter how poor central vision gets, your peripheral vision
-- the outer edge of your visual field, which does not depend
on the macula -- should stay useful. You should continue to
be able to see off to the sides. If vision in both eyes drops
to a level that eyeglasses cannot improve to better than 20/200
(the "big E" on the eye chart), the term "legal blindness"
is used. But don't let that frighten you. This is merely a
legal definition used to determine eligibility for certain
social services (and an extra income tax exemption).
is possible, even with no laser treatment, for the degenerative
process to stop before very much vision has been lost. But
it is more likely that central vision will continue decreasing,
probably to the point that reading is hampered and driving
a car is no longer safe. Remember, even if the degeneration
is severe, side vision typically remains normal. You should
continue to see well enough to move about comfortably and
care for yourself. Some patients even surprise everyone by
being able to see and pick up small objects from the floor.
You Can Do
addition to having regular eye exams, there is an easy and
important test you can do yourself. Take a few seconds every
day to check your vision with an Amsler grid, a card printed
with crossing lines that form small squares. Test each eye
separately, with the other eye covered. The lines should look
straight and solid. If any lines suddenly start looking wavy
or having missing segments, that could indicate the beginning
of wet changes that might be treatable, and you should make
an appointment to have your eyes examined within the next
is frightening to face the prospect of losing central vision.
But there are ways to use your remaining sight to best advantage.
Most people quickly learn how to use their peripheral vision
more effectively, such as by looking slightly off-center.
A low vision specialist can be a great help. This professional
can work with you to select magnification devices for seeing
better in specific situations. He or she will also introduce
you to non-optical aids, such as large-type books and magazines,
large press-on numbers for your appliances, and even talking
clocks. Consider joining a support group.
may find it comforting to talk to others who share similar
problems and exchange ideas with them. If your problem seems
especially overwhelming, you may wish to seek professional
psychological support. Always keep in mind that using your
eyes will never harm them. You can continue any of your usual
activities as long as you feel comfortable doing them. Even
with reduced vision, your life can be surprisingly normal
from Triad's Eye Care Notes
© 1989-2005 by Triad
Patients: for more information about your eyes, see: Taking
Care of Your Eyes: A Collection of the Patient Education Handouts
Used by America's Leading Eye Doctors