Definition
The lens of the eye focuses an image of the world on a portion of the retina
called the macula, the area of finest visual perception. After cataracts, damage
to the macula is the second most common cause of visual impairment in those over
65. Smoking, high blood pressure, and atherosclerosis are associated with
macular degeneration. Bright light also appears to play a role by creating
damaging natural substances in the eye, called free radicals. Gradual
deterioration of the macula is called macular degeneration.
In the most common form of macular degeneration, a substance known as lipofuscin
accumulates in the lining of the retina. A much less common form of macular
degeneration involves the abnormal growth of blood vessels. This can be treated
very successfully, if attended to soon enough, but may lead to irreversible
blindness if left untreated. For this reason, medical consultation in all cases
of macular degeneration (or any other type of vision loss) is essential.
Treatments
Principal Proposed Treatments for Macular Degeneration:
Zinc and Antioxidants;
Growing evidence suggests that a mixture of zinc and antioxidants can prevent or
slow the progression of macular degeneration.
A double-blind placebo-controlled trial evaluated the effects of zinc with or
without antioxidants on macular degeneration in 3,640 individuals in the early
stage of the disease. Participants were randomly assigned to receive one of the
following treatments: antioxidants (vitamin C 500 mg, vitamin E 400 IU, and
beta-carotene 15 mg), zinc (80 mg) and copper (2 mg), antioxidants plus zinc, or
placebo. The results indicate that zinc alone or, even better, zinc plus
antioxidants, significantly slowed the progression of the disease.
Note: Zinc at a dose of 80 mg daily can be harmful. One of the problems
is that high-dose zinc supplementation impairs copper absorption. That's why
extra copper was provided in the study described above. However, there may be
other risks as well. Physician supervision is advised. For other dosage and
safety issues, see the full zinc article.
Smaller studies of zinc for macular degeneration have found mixed results.
Other Proposed Treatments for Macular Degeneration:
Observational studies suggest that higher intake of dietary carotenes is
associated with a lower incidence of macular degeneration. Carotenes (carotenoids)
are a group of substances that are found in many fruits and vegetables,
especially yellow-orange and dark green ones. Beta-carotene is the most famous
carotene; however, in the absence of zinc supplements, beta-carotene (given
along with vitamin E and vitamin C) does not appear to be helpful.
The less well known carotenes lutein and zeaxanthin have also been investigated
for a possible role in preventing macular degeneration. These are principally
found in dark green leafy vegetables, such as spinach and collard greens. It has
been suggested that lutein may protect the macula from light-induced damage by
dyeing it yellow, thereby acting as a kind of natural sunglasses. It also acts
in the usual antioxidant fashion by neutralizing free radicals. However, one
observational study found little evidence of benefit with either lutein or
zeathanthin.
Flavonoids are another group of naturally occurring chemicals, found in many
plants, that may offer a variety of beneficial effects. Weak but interesting
evidence suggests that the flavonoid-rich herbs bilberry, ginkgo, and OPCs may
prevent or treat macular degeneration.
Moderate wine consumption might also help prevent macular degeneration. Like
these herbs, wine contains high levels of flavonoids.