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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.
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.
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
There, millions of cells change the light into nerve signals
that tell the brain what you are seeing. This is called your
central vision. With it, you are able 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 and Wet Macular Degeneration
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
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
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 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
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
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
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 from its
normal place at the back of the eye 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.
If you
notice any of these changes in your vision, contact your eye
care professional at once for an eye exam.
How is
AMD detected?
Eye care
professionals detect AMD during an eye examination that
includes:
Visual
acuity test: This
eye chart test measures how well you see at various
distances
Pupil
dilation:
This examination enables your eye care professional to see
more of the retina and look for signs of AMD. To do this,
drops are placed into the eye to dilate (widen) the pupil.
After the examination, your vision may remain blurred for
several hours
Tonometery:
This is a standard test that determines the fluid pressure
inside the eye. Increased pressure is a possible sign of
glaucoma, another common eye problem in people over age 60.
One of the most common early signs of AMD is the presence of
drusen
Drusen are tiny yellow deposits in the retina. Your eye care
professional 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, 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.
If your eye care professional suspects 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 your eye care professional evaluate leaking
blood vessels to determine whether they can be treated.
How
is AMD treated?
Dry AMD currently cannot be treated. But 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/Photodynamic therapy
The treatment involves injecting a special photodynamic dye into one of the veins of the body. The dye reaches the abnormal vessels in the retina. The laser is then used to selectively ablate these abnormal vessels alone, avoiding much damage to the relatively normal surrounding tissue. Laser treatment is best applied soon after the new blood vessels develop, before they have reached and damaged the fovea—the central part of the macula. But even if the blood vessels are growing right behind the fovea, the treatment can be of some value in stopping further vision loss. One usually requires more than one PDT laser sitting for complete treatment. Special injections have now been developed for injecting into the eye in addition to the laser treatment.
An Amsler grid is an easy chart type test available with us through which you can assess the progress or worsening of the disease. The test should be done on a daily basis at home. It is essential to see the chart with one eye at a time (with other eye covered). One has to wear their reading glasses and outline the distorted areas.
Special scans known as OCT (Optical coherence tomography) scan is used to detect and monitor progress of wet AMD. Also, Fundus Angiographies help to monitor progress of the disease.
How is
laser surgery performed?
Laser
surgery is performed in your eye care professional's office
or eye clinic. Before the surgery, he or she will: (1)
dilate your pupil and (2) apply drops to numb the eye. In
some cases, he or she also may numb the area behind the eye
to prevent any discomfort.
The lights in the office will be dim. As you sit facing the
laser machine, your eye care professional will hold a
special lens to your eye. You may see flashes of bright
green or red light.
You can leave the office once the treatment is done, but you
will need someone to drive you home. Because your pupils
will stay dilated for a few hours, you also should bring a
pair of sunglasses.
For the rest of the day, your vision may be a little blurry.
Your eye may also hurt a bit. This is easily controlled with
drugs that your eye care professional can suggest.
You will need to make frequent follow-up visits. During each
exam, you may have fluorescein angiography to make sure that
the blood vessels are not still leaking. If the vessels
continue to leak, you might need more laser surgery.
What can
you do to protect your vision?
Dry AMD.
If you have dry AMD, you should have your eyes examined
through dilated pupils at least once a year. This will allow
your eye care professional to monitor your condition and
check for other eye diseases as well.
You should also obtain an Amsler grid to use at home. This
will provide you with a quick and inexpensive test to
evaluate your vision each day for signs of wet AMD. It works
best for people who still have good central vision. 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 have an eye exam.
Wet AMD.
If you have wet AMD, it is important not to delay laser
surgery if your eye care professional advises you to have
it. After surgery, you will need to have frequent eye
examinations to detect any recurrence of leaking blood
vessels. Studies show that people who smoke have a greater
risk of recurrence than those who don't. 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.
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 usual
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
need low vision aids, your eye care professional can often
prescribe them or refer you to a low vision specialist. In
addition, groups and agencies that offer information about
counseling, training, and other special services are
available.
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