Macular Degeneration
Although many people are not aware of it, macular
degeneration, often called AMD or ARMD (for age-related macular degeneration),
is the leading cause of blindness in the world. The eye-health organization
Prevent Blindness America estimates that 13 million Americans have evidence
of AMD. The disease breaks down the macula, the light-sensitive part of
the retina responsible for the sharp, direct vision needed to read or
drive.
Macular degeneration is diagnosed as either dry (atrophic) or wet (exudative). The dry form is more common than the wet, with about 90% of AMD patients diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss.
Macular degeneration is more common in people over age 65, and whites and females tend to get the disease more than their counterparts. Most cases of macular degeneration are related to aging. It also can occur as a side effect of some drugs, and it appears to run in families.
Signs of AMD
Macular degeneration can produce a slow or sudden painless loss of vision.
If straight lines look wavy to you, or your vision seems fuzzy, or there
are shadowy areas in your central vision, you may be experiencing early
signs of AMD.
Often, the eyecare practitioner detects early signs of macular degeneration before you experience symptoms. This usually is accomplished through a visual field screening, a brief test that measures your peripheral vision. If the eyecare practitioner detects some defect in your peripheral vision, he or she will order a full visual field exam, a much longer test that provides more extensive information about your vision.
What Causes It?
The exact causes of age-related macular degeneration are still unknown.
The dry form of AMD may result from the aging and thinning of macular
tissues, depositing of pigment in the macula, or a combination of the
two processes. With wet ARMD, new blood vessels grow beneath the retina
and leak blood and fluid. This leakage causes retinal cells to die and
creates blind spots in central vision.
Factors that place you at a higher risk for AMD include having a family member with AMD, smoking, high blood pressure, farsightedness and obesity. Whites and females tend to get the disease more that their counterparts.
Many researchers and eyecare practitioners believe that
certain nutrients — zinc, antioxidants (vitamins A, C and E), lutein
and zeaxanthin — help lower the risk for AMD or halt the progression
of dry AMD. Dietary fat may be a factor as well. A study published in
the August 2001 issue of Archives of Ophthalmology found that consumption
of omega-3 fatty acids, which are particularly prevalent in fish such
as salmon, had a protective effect against advanced macular degeneration.
Meanwhile, consumption of omega-6 fatty acids, prevalent in vegetable
oils, was associated with an increased risk.
Some cases of macular degeneration are side effects of toxic drugs such as Aralen (chloroquine, an anti-malarial drug) or phenothiazine, rather than age-related. Phenothiazine is a class of anti-psychotic drugs, including Thorazine (chlorpromazine, which is also used to treat nausea and vomiting, and intractable hiccups), Mellaril (thioridazine), Prolixin (fluphenazine), Trilafon (perphenazine) and Stelazine (trifluoperazine).
Macular Degeneration Treatment
Vitamins and minerals. Many researchers and eyecare practitioners believe
that antioxidant vitamins, such as beta-carotene (vitamin A) and vitamins
C and E, may protect the macula from damage.
In fact, a recently published study of over 3600 people found that supplementation with vitamins C and E, beta-carotene and zinc reduced certain patients' risk of progressing to advanced AMD by about 28%. This number reflects those patients with a lot of intermediate or large drusen, but not those with limited intermediate drusen or multiple small drusen.
Top: An eye with dry ARMD showed soft drusen (yellow spots), which created
blind spots in the patient's vision and severely decreased visual acuity.
Bottom: Nine months after laser photocoagulation, the drusen almost disappeared
and visual acuity was 20/20.
500 milligrams (mg) of vitamin C
400 international units (IU) of vitamin E
15 mg of beta-carotene
and 80 mg of zinc oxide
Bausch & Lomb is now marketing these nutrients in one supplement,
called Ocuvite PreserVision.
Note that smokers should avoid beta carotene supplements, as they increase the risk of lung cancer in smokers and those who've recently quit.
The eyecare community does not agree on the benefits of zinc or antioxidant supplements: more study is needed, especially on the long-term effects of high-dose supplementation. Keep in mind also that too much of any vitamin or mineral may affect the body's ability to absorb other important nutrients.
Read more about how vitamins and other nutrients can affect the eyes
Visudyne drug treatment. For those with wet AMD, the Food and Drug Administration has recently approved Visudyne, the first-ever drug therapy for this form of the disease. It's only for those whose new blood vessels are characterized as "predominantly classic": about 40% to 60% of new wet AMD patients, according to Visudyne maker CIBA Vision.
In this treatment procedure, the doctor injects Visudyne
into your arm, then activates the drug by shining a laser into your eye.
In clinical trials, 67% of patients found that either their vision loss
stabilized or that their vision improved.
Laser treatment. Laser photocoagulation may help wet AMD patients by destroying
new blood vessels to prevent leakage. Scientists are currently studying
laser treatments for dry AMD as well.
Low vision devices for vision loss. Although much progress
has been made recently in ARMD treatment research, as things stand now,
any central vision lost to dry AMD will probably not be restored. Your
eyecare practitioner may ask you to check your vision with an Amsler grid,
a piece of paper with a black grid of lines. Viewing the Amsler grid separately
with each eye helps you monitor your vision loss.
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