General Description
Macular degeneration (also known as age-related macular degeneration,
or AMD) is a common eye disease of the macula, a small area in the
retina that helps produce sharp, central vision required for "straight
ahead" activities such as reading and driving. This central vision
gradually deteriorates in people with AMD. AMD is the leading cause
of severe visual impairment and blindness in Americans over 60.
According to the National Eye Institute (NEI), AMD causes visual
impairment in approximately 1.7 million Americans over the age of
65. In some cases, AMD progresses so gradually that people notice
little effect on their vision. In other cases, the disease progresses
faster, leading to drastic loss of vision in one or both eyes. There
are two forms of AMD, a "dry" form and a "wet" form.
Dry AMD
About 90 percent of people with AMD have the dry form. In dry
AMD, there is a gradual breakdown of light-sensing cells inside
the macula (retinal pigment epithelium, or RPE), reducing central
vision. The cause of dry AMD is still the subject of debate and,
as of this time, there is no medical treatment for the disease.
Studies suggest that oxidative damage to the RPE may contribute
to AMD development,1 and the role of dietary
antioxidants in prevention of the disease is currently under investigation.
Wet AMD
As the dry form of AMD progresses, delicate new blood vessels
develop beneath the macula. These new vessels often leak blood
and fluid, causing rapid damage to the macula and loss of central
vision, a condition known as wet AMD. Although only 10 percent
of those with AMD have this form of the disease, wet AMD accounts
for 90 percent of all AMD-related blindness. Some cases of wet
AMD can be treated with a surgical procedure in which a laser
is used to seal the new blood vessels and prevent further loss
of vision. However, only about 15 percent of wet AMD cases are
eligible for this procedure because, in most cases, the new blood
vessels are too close to the area of the macula where the visual
image is focused. Even with laser treatment, loss of vision may
progress, and the vision loss can't be repaired.
Nutritional/lifestyle considerations
Because oxidative damage to the macula is believed to contribute
to AMD, much research has focused on the role of antioxidants
in the prevention of the disease. High intake of carotenoids,
particularly lutein and zeaxanthin (the primary carotenoids in
the macula), appears to lower a person's risk of developing AMD.2-4
Some studies suggest that other antioxidants such as vitamin C,
vitamin E, and zinc may also have a protective effect.5,6
Consumption of moderate amounts of red wine also appears
to protect against the development of AMD, presumably due to the
high levels of antioxidant bioflavonoids found in grapes.7
High-cholesterol diets have been linked to the progression of
AMD, while fish consumption is associated with a reduced risk
for developing the disease.8 Sunglasses and
wide-brimmed hats may also be helpful because sun exposure is
believed to contribute to AMD by triggering the formation of free
radicals. Because studies have shown that smokers have an increased
risk of developing AMD, cigarettes should be avoided.9-12
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