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Related Macular Degeneration (ARMD) |
Age related macular degeneration or ARMD is the most common cause of irreversible
vision loss for people over the age of 60. It is estimated that 2.5 million people
in developed countries will suffer visual loss from this disorder and that there
are approximately 200,000 new cases diagnosed every year. Macular degeneration is most common
in people over the age of 65 but there have been some cases
affecting people as young as their 40s and 50s. Symptoms
include blurry or fuzzy vision, straight lines like telephone
poles and sides of buildings appear wavy and a dark or empty
area may appear in the center of vision.
What
is the Macula?
The macula is the small portion of the retina located at
the center of this light sensitive lining at the back of
the eye. Light rays from objects that we are looking at come
to a focus on the retina and are converted into electrical
impulses that are then sent to the brain. The macula is responsible
for sharp straight-ahead vision necessary for functions such
as reading, driving a car and recognizing faces. The
effect of this disease can range from mild vision loss
to central blindness. That is, blindness
"straight ahead" but with normal peripheral vision
from the non-macular part of the retina which is undamaged
by the disease.
Two
types of Macular Degeneration
Ninety percent of ARMD is of the "atrophic" or "dry"
variety. It is characterized by a thinning of the macular
tissue and the development of small deposits on the
retina called drusen. Dry ARMD develops slowly and
usually causes mild visual loss. The main symptom is
often a dimming of vision when reading. The
second form of ARMD is called "exudative" or
"wet" because of the abnormal growth of
new blood vessels under the macula where they leak
and eventually create a large blind spot in the central
vision. This form of the disease is of much greater
threat to vision than the more common dry type.
What
are the causes of ARMD?
Unfortunately, the cause of this eye condition
is not fully understood but it is associated with
the aging process. As we age, we become more susceptible
to numerous degenerative processes like arthritis,
heart conditions, cancer, cataracts and macular
degeneration. These conditions may be caused by
the body's overproduction of free radicals. During
the metabolic process, oxygen atoms with an extra
electron are released. These extra electrons
are quite destructive and cause cellular damage,
alter DNA, and are thought to be at least partially
responsible for many of the degenerative diseases
mentioned above. The production of these free radicals
is normal during metabolism but the body produces
its own "anti-oxidants" to neutralize
them. Some
of the vitamins in the food we eat also have anti-oxidant
properties. These are vitamins A, C, E and beta-carotene.
Unfortunately, smoking, poor nutrition and other
lifestyle factors result in the body producing
too many free radicals. For this reason, lifestyle
factors may contribute to the risk of ARMD. There
is some evidence to suggest that ARMD has a genetic
basis, as the condition tends to run in families.
The exact nature of this familial tendency, however,
has not been clarified. It has been suggested from
twin studies that there is a defect in the genes
responsible for the integrity and health of the
retina. Exposure
to certain types of light may also play a role.
Studies performed on fishermen in the Chesapeake
Bay suggest that long-term exposure to ultraviolet
light from the sun may increase the risk of ARMD
and other eye conditions such as the development
of cataracts It
has also been hypothesized that hyperopia or farsightedness
may also play a role in the development of the
disease. It is thought that the shortening of the
eye in hyperopia may cause changes in the membrane
below the macula and in its blood vessels. In
the dry form of the disease, some form of inflammation
may also be a factor although what causes the inflammation
is not known.
How
is it treated?
Although researchers are spending
a great deal of time investigating
the cause and treatment of ARMD,
there is no real cure available.
The goal of current treatment efforts
is to attempt to stabilize the condition. For
the more severe wet form of the disease,
doctors have tried laser photocoagulation.
This treatment, however, is not without
dangers and is only beneficial in
the very early stages of the condition,
which is why early detection is so
important. This technique involves
directing a beam of laser light at
the abnormal blood vessels in order
to destroy them and prevent their
leaking. Provided that the blood
vessels have not grown under the
macula, this treatment can be helpful
in arresting the progress of the
disease. If the blood vessels are
already under the macula, the laser
may cause scarring and permanent
vision loss. Several
new treatments are under development
and scientific evaluation. A
new type of treatment called photodynamic
shows promise. A drug, injected into
the arm travels to the affected eye
and is then exposed to a non-thermal
red light. This light activates the
drug to close and seal off the abnormal
blood vessels. The entire treatment
only takes about 30 minutes and requires
no anesthetic. Treatment
using proton beams, which release
power at predetermined target site
and depth, has also been experimentally
tested for treatment of wet-ARMD.
Are Vitamins and Nutrition
Useful?
No treatment exists for the dry form but many doctors recommend
that a combination of specific vitamins and minerals helps
slow the progression of the disease. Recently a study has
been published in The Archives of Ophthalmology (American
Medical Association)that provides conclusive evidence to
support this theory. Anti-oxidant vitamins may help to neutralize
the free radicals that are associated with this degenerative
process. Zinc, one of the most common trace minerals in our
body, is highly concentrated in the retina and surrounding
tissues and is a requirement for chemical reactions in the
retina. |
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