Macular Degeneration (AMD)
Age related macular degeneration (AMD) is one of the most common
causes of poor vision after age 60. AMD is a deterioration or
breakdown of the macula. The macula is a small area at the center of
the retina in the back of the eye that allows us to see fine details
clearly and perform activities such as reading and driving.
The visual symptoms of AMD involve loss of central vision. While
peripheral (side) vision is unaffected, one loses the sharp,
straight-ahead vision necessary for driving, reading, recognizing
faces, and looking at detail. Unfortunately, symptoms do not occur
until irreversible vision loss has occurred. It is important to
detect AMD before symptoms occur. Therefore, one should have an
annual eye examination with dilation of the pupils every year after
the age of 60.
Although the specific cause is unknown, AMD seems to be part of
aging. While age is the most significant risk factor for developing
AMD, heredity, blue eyes, high blood pressure, cardiovascular
disease, and smoking have also been identified as risk factors. AMD
accounts for 90 percent of new legal blindness in the US.
Nine out of 10 people who have AMD have the dry form (called
atrophic), which results in thinning of the macula (See Photo). Dry AMD takes many years to develop. Currently there is
no treatment for this form of AMD.
The wet form of AMD (called exudative) is less common (occurring in
one out of 10 people with AMD), but is more serious. In the wet form
of AMD, abnormal blood vessels may grow in a layer beneath the
retina, leaking fluid and blood and creating distortion or a large
blind spot in the center of your vision (See Photo). If the blood
vessels are not growing directly beneath the macula, laser surgery
is the only proven effective treatment, to date, for wet AMD.
The best treatment of AMD is prevention. Some research shows that
sunlight exposure may increase the risk of AMD, so routine use of
sunglasses with UV filters is recommended outdoors. Other research
shows that daily supplementation with antioxidant vitamins may
prevent vision loss in certain individuals who have moderately
advanced AMD.
Among people at high risk for late-stage macular degeneration (those
with intermediate AMD in both eyes or advanced AMD in one eye), a
dietary supplement of vitamins C, E and beta carotene, along with
zinc, lowered the risk of the disease progressing to advanced stages
by about 25 to 30 percent. However, the supplements did not appear
to benefit people with minimal AMD or those who have no evidence of
macular degeneration.
Light may affect the eye by stimulating oxygen, leading to the
production of highly reactive and damaging compounds called free
radicals. Antioxidant vitamins (vitamins C and E and beta carotene)
may work against this activated oxygen and help slow progress of
macular degeneration.
Zinc, one of the most common minerals in our body, is very
concentrated in the eye, particularly in the retina and macula. Zinc
is necessary for the action of over 100 enzymes, including chemical
reactions in the retina. Studies show some older people have low
levels of zinc in their blood. Because zinc is important for the
health of the macula, supplements of zinc in the diet may slow down
the process of macular degeneration.
It is very important to remember that vitamin supplements are not a
cure for AMD, nor will they restore vision you may have already lost
from the disease. However, specific amounts of certain supplements
do play a key role in helping some people at high risk for advanced
AMD to maintain their vision
Promising AMD research is being done on many fronts. In the
meantime, high-intensity reading lamps, magnifiers and other
low-vision aids help people with AMD make the most of their
remaining vision.
|
|
|
