As we age, the
macula (the small part of the retina at the back of the eye that provides
sharpness of vision) begins to break down and produces small white particles
called drusen, which are seen in a fundus photograph and in a cross-sectional
diagram above. These can be an early sign of macular degeneration, but they do
not usually cause vision loss by themselves and not all patients who develop
drusen go on to develop macular degeneration.
The dry or atrophic
form of age-related macular degeneration, seen above in fundus photography and
in a cross-sectional diagram, is the most common form of macular degeneration,
accounting for about 90 percent of cases. Although this form of macular
degeneration does not usually cause severe vision loss, it can progress to the
wet form, so patients who have it should see their ophthalmologist regularly.
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The wet or exudative form of
macular degeneration , seen here in fundus photography and in a cross-sectional
diagram, affects about 10 percent of macular degeneration patients. Wet macular
degeneration is caused by the growth of abnormal blood vessels at the back of
the eye that can leak fluid and blood. wet macular degeneration typically causes
significant vision problems in the affected eye and can progress very rapidly
and cause permanent vision loss.
What is macular degeneration?
The eye is often compared to a
camera. The front of the eye contains a lens that focuses images on the back of
the eye. This area, called the retina, is covered with special nerve cells that
react to light, like film in a camera.
These nerve cells are very close
together in the middle of the retina where the eye focuses the images that we
see. This part of the retina is called the macula.
What is age-related macular
degeneration?
There are two types of AMD - the
dry (atrophic) form and the wet (exudative) form. The dry form of macular
degeneration affects about 90 percent of patients and usually begins with the
formation of tiny yellow deposits called drusen in the macula. Drusen usually do
not cause serious loss of vision, but can cause distortion of vision. However,
for reasons that are not yet understood, sometimes drusen will cause the macula
to thin and break down, slowly leading to vision loss.
Wet macular degeneration occurs in
about 10 percent of AMD patients. It is caused by the growth of abnormal blood
vessels beneath the macula that can leak fluid and blood.
The wet form of macular
degeneration typically causes significant vision problems in the affected eye
and can progress very rapidly, causing permanent central vision loss.
The exact cause of age-related
macular degeneration is not known. AMD may be hereditary. If someone in your
family has or has had macular degeneration, you may be at higher risk for
developing the disease.
Both of these conditions are called
age-related macular degeneration. If there are no new blood vessels being
created, it is "dry" macular degeneration. When new blood vessels start to grow,
it is called "wet" macular degeneration.
Why do people get macular
degeneration?
The exact cause of macular
degeneration has not been found. Things like smoking, exposure to direct
sunlight over a period of years, a lack of vitamin A and some medical conditions
seem to make people more likely to get macular degeneration.
Some people also seem to inherit a
tendency to have macular degeneration. None of these things can really be said
to cause macular degeneration, however, and there is no sure way to prevent the
condition.
How does the doctor know whether
someone has macular degeneration?
The doctor may notice some things
during the examination, or the patient may mention symptoms, that could be
caused by macular degeneration. These are:
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The ability to see fine details when one is looking directly at an object,
no matter how close or far away it is, starts to decline.
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Vision changes so that straight lines look wavy or broken.
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Dark spots, lines, or shadows appear across the middle of the field of
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When these symptoms are caused by macular degeneration, they can occur in just
one eye or in both eyes. Usually, the problem is noticed first in one eye.
If any of these symptoms occur, it
is important to schedule an appointment with your doctor as soon as possible.
The doctor will use a special instrument to look inside the eye for signs that
the macula is changing.
How is macular degeneration
treated?
Only your doctor can recommend the
right treatment for macular degeneration. In the early stages of the condition,
your doctor might even recommend not treating it.
Instead, more frequent eye
examinations might be appropriate so the doctor can make sure that the macular
degeneration is not getting worse. It is important to keep these appointments.
Even though vision might not change for months at a time, macular degeneration
will never get better on its own. And when macular degeneration goes from the
"dry" form to the "wet" form, there can be a permanent loss of vision.
Is there any way to know if
macular degeneration starts to get worse?
People with macular degeneration
can check their own vision with a simple test called the Amsler grid.
The Amsler grid is a pattern of
straight lines that make perfect squares. The patient looks at a large dot in
the middle of the grid and notices any areas where the lines look blurry, wavy
or broken. If the grid lines seem to be more distorted than before, it might be
a sign that the macular degeneration is getting worse and needs treatment.
Surgeons have several techniques to
treat "wet" macular degeneration, including:
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Laser photocoagulation. This procedure is used to stop the abnormal growth
of blood vessels that happens in "wet" macular degeneration. The surgeon
focuses a laser beam onto a small spot on the macula where blood vessels are
growing. The laser beam heats up that spot, creating a tiny burn in the blood
vessels and stopping their growth. Unfortunately, vision does not come back in
the areas treated with the laser. It is also very likely that new blood
vessels will grow at some time in the future.
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Photodynamic therapy. In this treatment, a special dye is injected into
the bloodstream. This dye is actually a type of medication that only becomes
active when very strong light, such as a laser, is shined on it. The surgeon
activates the medication by focusing a laser onto the abnormal blood vessels
that are growing in the macula. The medication works from inside the blood
vessels to shrink them. This treatment causes much less damage to the macula,
so there is less loss of vision. But the growth of abnormal blood vessels
still might happen again in the future.
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Macular surgery. There are two other treatments the surgeon might
recommend for severe cases of "wet" macular degeneration. In both of these
procedures, the surgeon makes openings into the eye for special instruments.
One technique is to remove the tissue where the abnormal blood vessels are
growing. Another method is to lift the macula off the area where the blood
vessels are growing and place it in a more healthy part of the retina. These
procedures often do not fully restore normal vision, however. |
How successful is surgery to
treat macular degeneration?
None of these procedures will cure
macular degeneration, and vision that is lost often will not come back. Laser
photocoagulation and photodynamic therapy will greatly slow down the loss of
vision, however.
Does everyone with macular
degeneration eventually go blind?
No. Even though vision might be
blurry or lost in the middle of the field of view, macular degeneration does not
affect vision off to the side. And with the treatments available today, people
with macular degeneration have a good chance of keeping useful vision for many
years. The best way to keep and use as much vision as possible is to have
regular eye examinations and follow your doctor's advice.
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