What Is Age-Related Macular Degeneration?
Macular degeneration is the leading cause of severe vision loss in people
over age 60. It occurs when the small central portion of the retina, known as
the macula, deteriorates. The retina is the light-sensing nerve tissue at the
back of the eye. Because the disease develops as a person ages, it is often
referred to as age-related macular degeneration (AMD). Although macular
degeneration is almost never a totally blinding condition, it can be a source
of significant visual disability.
There are two main types of age-related macular degeneration:
- Dry form.
The "dry" form of macular degeneration is characterized by the
presence of yellow deposits, called drusen, in the macula. A few small
drusen may not cause changes in vision; however, as they grow in size and
increase in number, they may lead to a dimming or distortion of vision
that people find most noticeable when they read. In more advanced stages
of dry macular degeneration, there is also a thinning of the
light-sensitive layer of cells in the macula leading to atrophy, or tissue
death. In the atrophic form of dry macular degeneration, patients may have
blind spots in the center of their vision. In the advanced stages, patients
lose central vision.
- Wet form.
The "wet" form of macular degeneration is characterized by the
growth of abnormal blood vessels from the choroid underneath the macula.
This is called choroidal neovascularization. These blood vessels leak
blood and fluid into the retina, causing distortion of vision that makes
straight lines look wavy, as well as blind spots and loss of central
vision. These abnormal blood vessels eventually scar, leading to permanent
loss of central vision.
Most patients with macular degeneration have the dry form of the disease and
will not lose central vision. However, the dry form of macular degeneration can
lead to the wet form. Although only about 10% of people with macular
degeneration develop the wet form, they make up the majority of those who
experience serious vision loss from the disease.
It is very important for people with macular degeneration to monitor their
eyesight carefully and see their eye doctor on a regular basis.
What Are the Risk Factors for Macular Degeneration?
As the name suggests, age-related macular degeneration is more common in
older adults. In fact, it is the leading cause of severe vision loss in adults
over age 60.
Macular degeneration may be hereditary, meaning it can be passed on from
parents to children. If someone in your family has or had the condition you may
be at higher risk for developing macular degeneration. Talk to your eye doctor
about your individual risk.
Smoking, high blood pressure, high cholesterol, obesity, and being white are
also risk factors for macular degeneration.
What Are the Symptoms of Macular Degeneration?
In its early stages, macular degeneration may not have symptoms and may be
unrecognized until it progresses or affects both eyes. The first sign of
macular degeneration is usually a dim, blurry spot in the middle of your
vision. This spot may get bigger or darker over time.
Symptoms of macular degeneration include:
- Dark, blurry areas in the
center of vision
- Diminished or changed color
perception
If you experience any of these symptoms, see an eye specialist as soon as
possible.
How Is Macular Degeneration Diagnosed?
Age-related macular degeneration can be detected in a routine eye exam. One
of the most common early signs of macular degeneration is the presence of
drusen -- tiny yellow deposits under the retina. Your doctor can see these when
examining your eyes. Your doctor may also ask you to look at an Amsler grid --
a pattern of straight lines that resemble a checkerboard. Some of the straight
lines may appear wavy to you, or you may notice that some of the lines are
missing. These can be signs of macular degeneration.
If your doctor detects age-related macular degeneration, you may have a
procedure called angiography or an OCT. In angiography, a dye is injected into
a vein in the arm. Photographs are taken as the dye reaches the eye and flows
through the blood vessels of the retina. If there are new vessels or vessels
leaking fluid or blood in the macula, the photographs will show their exact
location and type. OCT is able to see fluid or blood underneath the retina
without using dye.
Early detection of age-related macular degeneration is very important
because there are treatments that can delay or reduce the severity of the
disease.
What Treatments Are Available for Macular Degeneration?
There is currently no cure for macular degeneration, but treatments may
prevent severe vision loss or slow the progression of the disease considerably.
Several options are available, including:
- Anti-angiogenesis drugs.
These medications (Avastin, Eyelea, Lucentis, Macugen) block the
development of new blood vessels and leakage from the abnormal vessels
within the eye that cause wet macular degeneration. This treatment has
been a major change in the treatment of this condition and many patients
have actually regained vision that was lost. The treatment may need to be
repeated during follow-up visits.
- Vitamins. A large
study performed by the National Eye Institute of the National Institutes
of Health, called AREDS (Age-Related Eye Disease Study), showed that for
certain individuals, vitamins C, E, beta-carotene, zinc and copper can
decrease the risk of vision loss in patients with intermediate to advanced
dry macular degeneration. Ask your eye doctor if these vitamin supplements
will benefit you before taking them.
- Laser therapy.
High-energy laser light can sometimes be used to destroy actively growing
abnormal blood vessels that occur in macular degeneration.
- Photodynamic laser
therapy. A two-step treatment in which a light-sensitive drug (Visudyne)
is used to damage the abnormal blood vessels. A doctor injects the drug
into the bloodstream to be absorbed by the abnormal blood vessels in the
eye. The doctor then shines a cold laser into the eye to activate the
drug, damaging the abnormal blood vessels.
- Low vision Devices.
Devices that have special lenses or electronic systems that produce
enlarged images of nearby objects. They help people who have vision loss
from macular degeneration make the most of their remaining vision.
Researchers are studying new treatments for macular degeneration. The
following treatments are considered experimental and have been used less often
since the development of anti-angiogenic medications have developed:
- Submacular surgery.
Surgery to remove the abnormal blood vessels or blood.
- Retinal translocation.
A surgical procedure used to destroy abnormal blood vessels that are
located directly under the center of the macula, where a laser beam cannot
be placed safely. In the procedure, the macular center is rotated away from
the abnormal blood vessels to a healthy area of the retina, thus
preventing the formation of scar tissue and further damage to the retina.
Once moved away from the abnormal blood vessels, a laser is used to treat
the abnormal blood vessels.
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What Is the Outlook for People With Macular Degeneration?
People rarely lose all of their vision from age-related macular
degeneration. They may have poor central vision, but they are still able to
perform many normal daily activities.
The wet form of macular degeneration is a leading cause of irreversible
vision loss. When both eyes are affected, you may experience a significant
decrease in your quality of life.
The dry form of age-related macular degeneration is much more common and
tends to progress more slowly, allowing you to keep most of your vision.
Unfortunately, even after wet macular degeneration treatment, the condition
can recur. Because of this, individuals with macular degeneration must test
their own vision regularly and follow the recommendations of their
ophthalmologist. Successful and timely treatment will slow the rate of vision
loss and often improve vision.