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Learn About Vitamins for Macular Degeneration

By Dr. Shantan Reddy

It is well recognized that oxidative stress likely contributes to the pathogenesis of age related macular degeneration. The retina’s defenses to such processes include glutathione (GSH) peroxides, catalases, and antioxidant nutrients such as vitamins E and C and carotenoids.   With this understanding, it has been hypothesized that people with low levels of these antioxidants may be more prone to oxidative damage in the retina, which may ultimately lead to age related macular degeneration. It is reasonable to speculate that consuming higher levels of these antioxidants may protect an individual from developing age related macular degeneration. This was hypothesized and proven by the Age-Related Eye Disease Study Group who showed that antioxidants and zinc supplements could reduce the risk of progression in some forms of age related macular degeneration.  More specifically, early age related macular degeneration (AREDS category 2), characterized by small and intermediate drusen with no or minimal pigment epithelial abnormalities in the macula, progressed to advanced age related macular degeneration in only 1.3% of cases at five years. Alternatively, intermediate age related macular degeneration (AREDS category 3), characterized by extensive medium-sized drusen ( ≥ 125 microns in diameter) in one or both eyes, and progressed to advanced age related macular degeneration in 18% of cases. No evidence was found to support the use of antioxidant vitamins and mineral supplementation in early age related macular degeneration. Conversely, patients with either intermediate or advanced age related macular degeneration (in one eye) benefited from a combination of antioxidant vitamin and mineral supplementation (AREDS formulation: Vitamin C 500mg, Vitamin E 400 IU, Beta-carotene 15 mg, Zinc oxide 80 mg, and Cupric oxide 2 mg).  The relative risk of developing advanced age related macular degeneration (in the other eye in the advanced age related macular degeneration group) was reduced by 25%, and the relative risk of vision loss of three or more lines was reduced by 19%.  Since studies also found that beta-carotene increased the risk of lung cancer in smokers, it was recommended that smokers consider omitting beta-carotene from the formulation.  Lutein and zeaxanthin, major components in macular pigment, may reduce the likelihood of having advanced age related macular degeneration. Direct evidence of neuroprotection is still lacking but it is hypothesized that macular xanthophylls play a role as: an important structural molecule within cell membrane, a modulator of intra- and extra-cellular reduction-oxidation balance; and a short-wavelength light (which is damaging to retinal tissues) filter In the same way, omega-3 LCPUAs present some structural and functional properties which indicate a probable role in visual-sensory process and as a protective factor against retinal diseases . Indeed, inverse relationship of dietary omega-3 LCPUFA intake with advanced age related macular degeneration has been reported in different studies.  Studies investigating the impact of lutein and omega-3 fatty acids on the incidence and progression of age related macular degeneration provided conflicted results, though they have been shown to be non-toxic to the retina. In response, AREDS 2, which started in late 2006, is a multicenter randomized phase III study designed to assess the effects of oral supplementation of high doses of macular xanthophylls (lutein and zeaxanthine) and omega-3 LCPUFAs [docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)] for the treatment of age related macular degeneration and cataract. This study will enroll 4,000 subjects for a six year period. In addition to the intake of vitamin and minerals supplements described by the AREDS study, stopping smoking and a healthy diet are strongly recommended.

Dietary supplementation with the AREDS formulation of vitamins has clearly been shown in the AREDS I trial, a large, prospective, randomized, placebo-controlled trial, to be of benefit in patients with intermediate and advanced age related macular degeneration (Categories 2-3).  Ophthalmologists and patients should educate themselves as to which products and dosages are consistent with the AREDS recommendations. Additionally, instructing patients to consume diets rich in fruits and vegetables, particularly green leafy and yellow-orange vegetables, is reasonable.

Understanding the beneficial effects of vitamin supplementation has drastically changed how we approach patients with non-neovascular age related macular degeneration. It allows us an avenue to halt a relentless and destructive disease. Preventing disease progression is far preferable to treating it once vision loss has occurred. We are anxiously waiting to learn if lutein, zeaxanthin, and omega-3 fatty acids will prove to be protective against the development of advanced age related macular degeneration. The results from AREDS II will ultimately determine whether these should be added to the currently accepted formulations. As we continue to make headways in understanding the various etiologies of age related macular degeneration, we will be empowered to develop newer and more effective means of prevention, and hopefully someday find a cure.

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Topics and Subtopics: Eye Care

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