The lens of the eye focuses an image of the world on a portion of the retina called the
, the area of finest visual perception. Gradual deterioration of the macula is called macular degeneration. After
, damage to the macula is the second most common cause of visual impairment in those over 65.
high blood pressure
are associated with progressive damage to the macula. Ultraviolet light may also play a role by creating harmful free radicals in the eye.
In the most common form of macular degeneration (dry 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 (wet macular degeneration). 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.
Principal Proposed Natural Treatments
: The treatments described in this section are intended as support to standard ophthalmalogical care, not as a substitute for it. In addition, all studies refer primarily to the more common type of macular degeneration, dry macular degeneration.
Zinc and Antioxidants
A single solid study suggests that zinc, or a mixture of zinc and antioxidants can prevent or slow the progression of early macular degeneration. However it is not clear whether the antioxidant portion of this mixture added any additional benefit.
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 (
at 500 mg,
at 400 IU, and
at 15 mg), zinc (80 mg) and
plus zinc, or placebo. The results indicate that zinc alone or zinc plus antioxidants, significantly slowed the progression of the disease.
: Zinc at doses of 80 mg and higher 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
Smaller studies of zinc for macular degeneration have found mixed results.
Note that it’s not clear how much the antioxidants in the mixture contributed to the benefits. In fact, there is no convincing evidence that antioxidants alone are effective for preventing or delaying the onset of macular degeneration. A 4-year, double-blind, placebo-controlled trial of 1,193 people with macular degeneration failed to find vitamin E alone helpful for preventing or treating macular degeneration.
An even larger and longer study, following over 20,000 people for over 10 years, failed to find that beta-carotene alone reduced the incidence of macular degeneration.
A mixture of beta-carotene, vitamin E, and vitamin C has also failed to prove beneficial.
And, a review of 3 randomized controlled trials involving a total of 23,099 subjects found no evidence of benefit for vitamin E and beta-carotene.
Lutein and Other Carotenoids
are a group of substances that are found in many fruits and vegetables, especially yellow-orange and dark green ones. (
is the most famous carotenoid).
suggest that higher intake of dietary carotenoids is associated with a lower incidence of macular degeneration.
However, observational studies prove little about cause and effect. To determine whether carotenoids can actually prevent or treat macular degeneration, double-blind, placebo-controlled studies are necessary. (For information on why this is the case, see
Why Does This Database Rely on Double-blind Studies?
As noted above, in one very large study, beta-carotene failed to prove effective for preventing macular degeneration. However, the less well-known carotenoids lutein and zeaxanthin might be more promising.
These carotenoids, principally found in corn and dark green leafy vegetables, are found in high concentrations in the eye. It has been suggested that they may protect the macula from light-induced damage by dyeing it yellow, thereby acting as a kind of natural sunglasses. They also act in the usual antioxidant fashion by neutralizing free radicals.
These hopes received support from a double-blind, placebo-controlled trial.
This study enrolled 90 people with dry macular degeneration and followed them for 12 months. The participants received either lutein (10 mg), lutein plus antioxidants and a multivitamin/mineral supplement, or placebo. At the end of the study period, participants who had taken lutein alone or lutein plus the other nutrients showed improvements in vision, while no change in vision was seen in the placebo group. A subsequent study failed to find benefit with lutein, but it used a lower dose (6 mg daily) and involved fewer people.
Ultimately, further study will be needed to establish whether lutein is actually helpful for macular degeneration. For more information, see the full
Other Proposed Natural Treatments
Like carotenoids, flavonoids are found in many plants and may offer a variety of beneficial effects. Weak but interesting evidence suggests that
(OPCs), both rich in flavonoids, may prevent or treat macular degeneration.
also contains many flavonoids and is additionally thought to increase circulation. In a 6-month, double-blind, placebo-controlled study of 20 people with macular degeneration, use of ginkgo at a dose of 160 mg daily resulted in improved visual acuity.
Furthermore, positive results were seen in a 24-week, double-blind study of 99 people with macular degeneration that compared ginkgo extract at a dose of 240 mg per day against ginkgo at a dose of 60 mg per day.
Vision improved in both groups, but to a greater extent with the higher dose. This study would have been more meaningful if it had included a
group, but nonetheless, “dose-related” effects of this type hint that a treatment may really work. It has been suggested that ginkgo aids vision by increasing blood flow to the optic nerve. However, one study designed to evaluate this possible mechanism of action failed to document such an effect.
Weak evidence hints that moderate wine consumption might help prevent macular degeneration.
Similarly weak evidence suggests possible benefit with a
low glycemic index
In observational studies, people who happen to consume a diet rich in
omega-3 fatty acids
(fish oil) seem to lower their risk of macular degeneration. However, in the absence of randomized controlled trials, it is not possible to say whether or not it is the omega-3 that produces this benefit.
One controlled study that unfortunately failed to use a
appeared to find benefit with a combination of