There is evidence for an inverse association between the amount of macular pigment (MP) in the retina and risk of age-related macular degeneration (AMD). Dietary supplementation with lutein (L) or zeaxanthin (Z) can significantly increase MP density. These findings are relevant to an intervention study, the long-term goal of this research, to determine the efficacy of L and Z in preventing or delaying AMD. Heterochromatic flicker photometry (HFP) is a commonly used method for measuring MP density, but HFP is not suitable for many subjects, particularly those whose vision is impaired by AMD.
Specific aim 1 is to develop a simple, inexpensive, objective, reflectance method of measuring MP density, suitable for an L or Z intervention study. The method will utilize a retinal camera equipped with a triple-band interference filter. The system will be designed so that 3 fundus images at different wavelengths may be extracted from a single image. Image analysis software will be used to generate an MP density map from these images. The wavelengths will be chosen to minimize the potential influence of photopigments and melanin on the measured densities. The validity of the technique will be investigated by comparing MP densities obtained by HFP and by the new reflectance method.
Specific aim 2 is to compare the effects of L and Z supplementation, at 20 mg per day for 6 months, on L and Z concentration in the blood serum and on the density of MP determined by the reflectance method. Fifty subjects will participate. On a random basis, 20 will be assigned to each of the supplements and 10 will be assigned to a placebo. For a subset, HFP will also be used to monitor changes in MP density for comparison with reflectance data. The concentration of L and Z in the serum will be measured by HPLC. The study will quantify differences in response to supplementation in subjects, and will seek causes. Preliminary data indicate that the rate of increase in MP is driven by the serum concentration of L+Z.
Specific aim 3 is to compare the reflectance and HFP methods for subjects with early-stage AMD. On average, such subjects may be expected to have below normal MP densities. Fourteen subjects will participate in a similar L trial to that in specific aim 2. The trial will permit evaluation of the reflectance method in subjects for whom HFP is likely to prove unsuitable. It will also determine their responsiveness to L supplementation.
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