To study the effects of age and of n-3 fatty acids, lutein, and zeaxanthin on the retinal pigment epithelium (RPE).
Rhesus monkeys (age range, 7-17 years; n = 18) were fed xanthophyll-free semipurified diets from birth. The diets had either low or adequate amounts of n-3 fatty acids. Six monkeys remained xanthophyll-free until death. Six received supplements of pure lutein and six of pure zeaxanthin for 6 to 24 months. The central retina was serially sectioned, and the number of RPE cells were counted in an 8-microm strip along the vertical meridian. Cell counts were compared with data from control monkeys (n = 15) fed a standard laboratory diet.
Foveal and parafoveal RPE cell densities increased with age. Xanthophyll-free monkeys had a dip in the RPE cell density profile at the foveal center, rather than the normal peak. After supplementation with xanthophylls, the RPE profile of animals low in n-3 fatty acids no longer had a dip at the foveal center but became asymmetric, with higher densities in the inferior retina. In animals with adequate n-3 fatty acid levels, xanthophyll supplementation did not restore the foveal peak, and resulted in an asymmetric profile with higher densities in the superior retina.
RPE cells are sensitive to the absence of macular pigment. Supplemental xanthophylls interact with n-3 fatty acid levels to produce asymmetries in the RPE profile. Xanthophylls and n-3 fatty acids are essential for the development and/or maintenance of a normal distribution of RPE cells.