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WHAT IS MACULAR
What Is Macular Degeneration?
Age-related macular degeneration
(ARMD) is the
most common cause of irreversible vision loss in Americans over the age of 60.
It is estimated that 10 million Americans will experience this age-related
visual impairment during their retirement years.
degeneration is a disorder of the retina, the light-sensitive inner lining of
the back of the eye. The macula is a small, central portion of the retina which
is necessary for sharp, "straight ahead" vision needed for reading,
driving a car or recognizing faces.
There are a number of abnormalities associated
with the term "age-related macular degeneration." They range from mild
changes with no decrease in vision to abnormalities severe enough to result in
the loss of all "straight ahead" vision. Macular degeneration does not
cause total blindness because the remaining and undamaged parts of the retina
around the macula continue to provide "side" vision.
There are two main types of macular degeneration,
"dry" and "wet," both are discussed in the next section.
Signs and Symptoms
Aging causes the cells in the retina to become
less efficient. Ultimately, deposits called drusen appear under the retina and
can be seen during an eye examination and on photographs of the
retina . A few
small drusen may cause no decrease in vision (photo 1). However, if too many large drusen
develop, vision will decrease (photo 2). Vision may also be affected when there are
disturbances in the layer of cells below the retina called the retinal pigment epithelium. These
two types of changes are known as "dry" and "wet" macular degeneration.
Dry is the most common form and currently, there are no known
treatments for dry AMD.
The Early Stages of Dry ARMD
Atrophic Stages of Dry ARMD
The majority of
people with macular degeneration have an early form of the condition and
experience minimal visual loss. For many of these people, macular
degeneration will not progress to a more serious condition.
degeneration progresses to visual loss, 90% of the affected people will
develop the dry, or atrophic form of the disease.
The other 10% of
people will develop a more serious condition known as the Wet, or
exudative, form of macular degeneration.
A few people experience the
"wet" form of macular degeneration which can cause more severe visual
loss (photo 3). In this situation, abnormal blood vessels grow beneath the retina and
result in bleeding and leakage of fluid. Vision may suddenly become distorted or
blurred. In some cases of wet macular degeneration, laser treatment can be
effective at destroying the abnormal vessels, thus preventing or slowing further
visual loss. Wet macular degeneration cannot always be treated successfully by
laser, however, some experimental drugs and new surgical procedures
(photodynamic therapy) are being
the search for better methods to combat wet age-related macular
degeneration, drug therapy is emerging as one of the most promising
weapons of choice.
blood vessel growth (neovascularization) is set off by a complex
series of interactions in the cell. A protein molecule called
vascular endothelial growth factor (VEGF), signals cells to produce
these misguided vessels. Most of the drugs being developed for
wet AMD are designed to target VEGF one way or another to inhibit
this unwanted blood vessel growth and reduce leakage and bleeding.
This is the first anti-VEGF ophthalmic drug approved by the Food
and Drug Administration, Macugen became available in clinical
practices last January. It is delivered by injection to reach
the back of the eye. Patients typically receive injections
every sex weeks for two years and show minimal side
effects. Phase III clinical trials of Macugen have found
that treated patients has a 27% greater chance of avoiding
moderate visual loss.
(ranibizumab) This VEGF antibody is on the final phase of
clinical trials and may receive FDA approval in 2006. One
year results from two studies on Lucentis were very
encouraging. The substance is a modified version of the
drug Avastin (see below), which is used to treat colorectal
cancer. It also is injected directly into the eye every
mid-July 2005, Genentech officials reported that Lucentis
potentially could improve vision in a significant number of
macular degeneration patients who already have experienced
vision loss from the "wet" form of the disease.
data is very compelling because, for the first time, there is a
potential treatment which has been shown to improve vision in a
significant number of patients with wet AMD as opposed to just
slowing progression of vision loss.
(bevacizumab) This drug, from which Lucentis is derived, is
being explored as a therapy for wet AMD. Early study
results of Avastin, which is injected directly in the eye, have
been encouraging. In addition, the cost of this treatment
is significantly less than the other anti-VEGF drugs.
However further studies are needed to determine its safety and
(squalamine lactate) Evizon is the first clinical drug candidate
in a class of naturally occurring molecules know as
aminosterols. It is a potent molecule that blocks the
action of a number of angiogenic growth factors, including
VEGF. The drug, which is given by intravenous
infusion, has been tested for several types of cancers, in
addition to wet AMD. Phase II trials of Evison for AMD
showed positive results, with the patients experiencing stable
or improved vision.
acetate) This anti-inflammatory drug is being used to minimize
blood vessel growth. It is being studied in conjunction
with photodynamic therapy (PDT) to reduced the persistence or
growth of abnormal blood vessels.
acetate) This steroid compound, delivered behind the eye using a
blunt-tipped, curved tool, continues to be studied.
Treatments are spaced about six months apart.
therapy (PDT) with Visudyne
Supplements For ARMD
Thermotherapy (TTT) Photocoagulation
Macular Surgery with Tissue
Plasminogen Activator (TPA).
Implant or Transplant
of Retinal Cells
A Self Test
The Amsler Grid (see figure below, for a further explanation and printed copy, see the Amsler
Grid page) is used to screen for macular degeneration.
In an effort to detect loss of vision associated with macular degeneration, eye
doctors across the country are recommending this test to their patients. The
test involves looking at a square grid with a dot in the center. The grid should
be held 12 inches away from the face. While wearing eye glasses normally worn
when reading, the individual covers one eye at a time. With the uncovered eye,
the individual stares at the dot in the center of the grid. All four corners of
the grid should be visible, and the lines of the grid should appear to be
straight and continuous from top to bottom and side to side. If there appear to
be any holes or blurry spots, or the lines look wavy, fuzzy, crooked, distorted
or broken, the individual should call their eye doctor immediately.
view of Amsler Grid
here If you would like a printed Amsler Grid with instructions.
Today's advances in medicine means that more and more older Americans will be
able to maintain good vision as they age. Since many serious eye
conditions are treatable when detected at an early age, it is important to have
periodic eye examinations from an
eye care , especially as one approaches the sixth decade of