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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.
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.
AMD occurs in two forms:
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 severe vision loss 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.
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 two 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 properly. Over time, the blurred spot
may get bigger and darker, 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.
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