Macular degeneration is an eye disease that occurs
when the small central portion of the retina, known as the macula, is damaged.
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).
There are two types of age-related AMD, the "dry" form
and the "wet" form.
- Dry form of AMD: The "dry" form of AMD is characterized by the
presence of yellow deposits, called drusen, in the macula. In general,
drusen does 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
AMD, 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 AMD,
patients may have blind spots in their vision. In the advanced stages,
patients may even lose central vision.
- Wet form of AMD: The "wet" form, or exudative neovascular form of
AMD 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 eye, 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 AMD have the dry form of the
disease and will not lose central vision. However, the dry form of AMD can lead
to the wet form. Although only about 10% of people with AMD develop the wet
form, they make up the majority of those who experience serious vision loss from
the disease.
Because the dry form can change into the wet form, it
is very important for people with AMD to monitor their eyesight carefully and
see their eye doctor on a regular basis.
Who gets AMD?
As the name suggests, AMD is more common in older adults. In fact, it is the leading cause
of severe vision loss in adults over age 60.
AMD 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 the disease. Talk to your
eye doctor about your individual risk.
What are the symptoms?
AMD often does not have symptoms and is unrecognized
until it affects both eyes. The first sign of AMD is usually distortion of
straight lines. This may progress to a gradual loss of central vision.
Symptoms of AMD include:
- Straight lines start to appear distorted, or the center of vision
becomes distorted
- Dark, blurry areas or white out appears in the center of vision
- Diminished or changed color perception
If you experience any of these symptoms, see an ophthalmologist as soon as possible.
How is AMD diagnosed?
One of the most common early signs of AMD is the
presence of drusen -- tiny yellow deposits under the retina. Your doctor can see
these during a routine eye exam. 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 AMD. Sometimes, early AMD can even be
detected using a traditional eye chart exam.
If your doctor suspects you have the rare "wet" form,
or neovascular form, of AMD, you may have a procedure called fluorescein
angiography. In this procedure, a dye, called fluorescein, is injected into the
arm. Photographs are taken to show the movement of the dye as it reaches the eye
and passes through the blood vessels of the retina. If there are new vessels
leaking fluid or blood in the macula, the photographs will show their exact
location and their type.
Early detection of AMD is very important because there
are treatments that can delay or reduce the severity of the disease.
What treatments are available?
There is currently no cure for AMD, but treatments may
prevent severe vision loss and slow the progression of the disease considerably.
Several options are available, including:
- Anti-angiogenesis drugs: Ranibizumab (Lucentis®) is the
first drug in this new class to receive FDA approval for the treatment of
the ‘wet’ form of macular degeneration. This drug – and the goal of other
anti-angiogenesis drugs being tested – is to slow down or prevent the growth
of the abnormal blood vessels.
- Vitamins: Vitamins C, E, beta carotene, zinc and copper have been
shown to decrease the risk of vision loss in patients with intermediate to
advanced dry AMD. Ask your eye doctor if these vitamin supplements will
benefit you before taking them.
- Laser therapy: High-energy lights are used to destroy actively
growing abnormal blood vessels.
- Photodynamic laser therapy: A two-step treatment in which a light
sensitive drug 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 aids: Devices that have special lenses or electronic
systems that produce enlarged images of nearby objects. They help people
with partial vision make the most of their remaining vision.
Researchers are studying new treatments for AMD. The following treatments may soon be available,
but are currently considered experimental.
- External beam radiotherapy: This procedure uses a low-dose radiation
beam to prevent abnormal blood vessels from leaking. The blood vessels are
treated at a layer of the eye that does not harm the retina.
- 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.
- Gene transfer therapy: This technology involves inserting the
desired genetic material into a patient’s own cells, which would then either
guide the killing of abnormal cells or lead the growth of new cells to
replace damaged cells. In the case of macular degeneration, this technology
is investigating killing the cells that cause loss of vision (the epithelial
cells) and/or replacing the light-capturing cells in the retina that are
unable to be repaired once damaged.
What is the outlook for people with AMD?
Unfortunately, AMD can recur even after successful
treatment. The various procedures, however, can slow the rate of vision loss and
hopefully preserve some sight.
Next: Reviewed by the doctors at The Cleveland Clinic Cole Eye Institute.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 1/26/2010...#10704
