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Introduction
Age-related macular degeneration (AMD) is the most
frequent cause of vision loss among people 50 years and
older in the western world. Many older people are
unaware that they have AMD and may not notice that their
vision is deteriorating, particularly if only one eye is
affected. Other people may fail to report vision loss
because they believe it to be an inevitable consequence
of aging. If patients with certain types of AMD are to
benefit from recent developments in treatment, it is
important that the condition be diagnosed as early as
possible.
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Drusen |
AMD can be classified as either non-neovascular or
neovascular. Non-neovascular AMD (also known as 'dry'
AMD) is characterized by drusen, which appear as small
yellow deposits underneath the retina. Non-neovascular
AMD rarely causes severe vision loss unless central
atrophy develops. However, it is important to monitor
people with non-neovascular AMD because they may
progress to neovascular AMD.
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Central
Vision Deterioration |
Approximately 90% of patients with severe vision loss
from AMD have the neovascular form (also known as 'wet'
or 'exudative' AMD). Neovascular AMD is characterized by
the presence of choroidal neovascularization (CNV),
which develops when abnormal new blood vessels
proliferate underneath the retina. The main symptoms of
neovascular AMD are deterioration in central vision,
blind spots, and a distortion of vision. Definitive
diagnosis and classification of CNV requires fluorescein
angiography and color fundus photography of the retina.
The location of neovascular lesions is an important
factor affecting the progression of neovascular AMD and
the risk of vision loss. Eyes with subfoveal lesions
(those that extend under the center of the retina) are
at the greatest risk of vision loss.
Management of AMD
Non-neovascular AMD
At present, no intervention has been proven to reduce
the risk of developing non-neovascular AMD and there is
no treatment that has been shown to reverse the
condition. The Age-Related Eye Disease Study (AREDS) has
shown, however, that some patients with non-neovascular
AMD may benefit from supplementation with antioxidants
(vitamin C 500 mg, vitamin E 400 IU, and beta carotene
15 mg) and zinc 80 mg to reduce the risk of vision loss
arising from progression to advanced AMD.
Neovascular AMD
When abnormal vessel growth is located away from the
fovea, standard laser photocoagulation is performed when
appropriate. When vessels course underneath to center of
the retina, photodynamic therapy may be suggested.
Photodynamic therapy with
verteporfin (known as verteporfin therapy or Visudyne®
therapy) involves two steps: the drug is administered by
intravenous infusion and then activated in the target
area with a specially designed non-thermal laser.
Verteporfin therapy consists of a series of treatments
given as often as every 1-3 months if fluorescein
leakage from subfoveal neovascular lesions is seen on
angiography. At the initial visit, or if treatment is
indicated at a follow-up visit, patients receive
verteporfin by intravenous infusion over 10 minutes. The
laser light is applied 15 minutes after the start of
infusion. In the clinical trials, patients received a
mean of 3.4 treatments in the first year. Patients
should avoid exposure to direct sunlight or strong
indoor light for 5 days.
Several other treatments involving medications, laser
and surgery are being studied to determine whether or
not they are beneficial to patients with neovascular
AMD. As results become available, if any of the various
treatments are successful, they may be added to the
arsenal used to treat this common and often devastating
disorder.
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