Antioxidants, Omega-3 and Dry AMD
Dry, atrophic, or non-exudative, age-related macular degeneration (AMD) is the most common form of the disease, and is characterized by progressive devitalization of retinal pigment epithelium (RPE) and the formation of fatty deposits under the RPE known as soft drusen. Patients not receiving treatment have demonstrated a loss of visual acuity at 6 months of at least 0.8 lines and up to 1.5 lines.
Studies have suggested that nutritional factors can play a significant role in slowing the onset or limiting the effects of AMD. In 2004, the Lutein Antioxidant Supplementation Trial (LAST) demonstrated that nutritional supplementation with lutein or lutein together with antioxidants, vitamins and minerals improved visual function and symptoms in male patients with atrophic AMD (1). Currently, the 2nd Age-Related Eye Disease Study (AREDS II) is examining the effects of carotenoids and omega-3 fats on AMD.
The Taurine, Omega-3 Fatty Acids, Zinc, Antioxidant, Lutein (TOZAL) study was conducted to investigate the impact of combined omega-3, antioxidants, and other nutrients on visual function in those with atrophic AMD (2). The results suggest that such a nutritional approach may help maintain visual acuity.
Study Design and Methods
The primary objective of this prospective, open case-controlled study was to measure the change from baseline in visual function - Best-Corrected Visual Acuity (BCVA) via the ETDRS chart, contrast sensitivity, central 10 degree visual fields and retinal imaging (angiograms and photographs) at 6 months in subjects with atrophic (dry) AMD treated with a targeted nutritional supplement.
Thirty seven mixed gender patients with a mean age of 76.3 +/- 7.8 years were enrolled at 5 independent study sites and received standard of care along with a nutritional supplement containing lutein; zeaxanthin; vitamins A, C and E; beta-carotene; taurine; zinc, copper; EPA and DHA. Results were compared to a placebo cohort constructed from the literature that was matched for inclusion and exclusion criteria. A paired t-test was used to test a null hypothesis and a two-sided alpha level of 0.05 was used to determine statistical significance.
Seventy-six percent of subjects receiving the nutritional supplement demonstrated stabilization or improvement of BCVA at 6 months. Subjects gained an average of 0.0541 logMAR or one-half of a line of visual acuity (VA) over the 6-month period. There was a statistically significant improvement in VA from baseline (p = .045).
"The results provide strong evidence that the treatment being studied produces an improvement in VA" according to the authors. Supplementation increased VA above the expected baseline decrease in the majority of patients in this population. The results of the TOZAL study agree with the LAST and CARMIS studies and are predictive for positive visual acuity outcomes in the AREDS II trial. However, supplementation for longer than 6 months is likely required to effect changes in additional visual parameters.
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