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Macular degeneration is a condition that damages the macula, the
central part of the retina. The macula is responsible for
central vision and the ability to see detail. When the macula is
damaged, the eye loses its ability to see detail, such as small
print, facial features or small objects. The damaged parts of
the macula often cause scotomas, or localized areas of vision
loss. When you look at things with the damaged area, objects may
seem to fade or disappear. Straight lines or edges may appear
wavy.
Types of macular degeneration include dry macular
degeneration and wet macular degeneration. Ninety
percent of people who have macular degeneration have the dry
form of the condition. In dry macular degeneration, waste
products may accumulate in the tissues underneath the macula
forming yellowish deposits called drusen. The continued presence
of drusen interferes with the blood flow to the retina and, in
particular, to the macula. Less blood flow reduces the
nourishment to the macula causing its light sensitive cells to
stop working efficiently, or atrophy. You will sometimes hear
dry macular degeneration referred to as atrophic macular
degeneration. People who have dry macular degeneration may
experience a gradual loss of detail vision.
Though the wet form of macular degeneration affects only 10
percent of people diagnosed with the disease, it accounts for
almost 90 percent of the severe vision loss associated with the
condition. Dry form patients who have large drusen without clear
borders or who have many drusen that run together are at greater
risk for developing the wet form of the disease. With wet
macular degeneration, new weak blood vessels may grow in or
under the retina causing fluid and blood to leak into the space
under the macula. As a result, wet macular degeneration is
sometimes called exudative macular degeneration. (An "exudate"
is material, such as fluid, which has escaped from blood vessels
and has been deposited in tissues.) Wet macular degeneration is
also described as choroidal neovascularization. The choroid is
the area of blood vessels beneath the retina, and
neovascularization refers to growth of new blood vessels in
tissue. In choroidal neovascularization, blood vessels from the
choroid grow into the macula.
Symptoms of both the dry and wet form of AMD cause no pain. The
most common early sign of dry macular degeneration is blurred
vision. As fewer cells in the macula are able to function,
people will see details less clearly in front of them, such as
faces or words in a book. If the loss of these light-sensing
cells becomes great, people may see a small – but growing –
blind spot in the middle of their vision. The classic early
symptom of wet macular degeneration is that straight lines
appear crooked. This occurs when fluid from the leaking blood
vessels gathers and lifts the macula, distorting vision. A small
blind spot may also appear in wet macular degeneration,
resulting in loss of one's central vision.
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