Nutritional manipulation of primate retinas, V: effects of lutein, zeaxanthin, and n-3 fatty acids on retinal sensitivity to blue-light-induced damage

Abstract

Purpose: Blue-light photooxidative damage has been implicated in the etiology of age-related macular degeneration (AMD). The macular pigment xanthophylls lutein (L) and zeaxanthin (Z) and n-3 fatty acids may reduce this damage and lower the risk of AMD. This study investigated the effects of the lifelong absence of xanthophylls followed by L or Z supplementation, combined with the effects of n-3 fatty acid deficiency, on acute blue-light photochemical damage.

Methods: Subjects included eight rhesus monkeys with no lifelong intake of xanthophylls and no detectable macular pigment. Of these, four had low n-3 fatty acid intake and four had adequate intakes. Control subjects had typical L, Z, and n-3 fatty acid intake. Retinas received 150-μm-diameter exposures of low-power 476-nm laser light at 0.5 mm (∼2°) eccentricity, which is adjacent to the macular pigment peak, and parafoveally at 1.5 mm (∼6°). Exposures of xanthophyll-free animals were repeated after supplementation with pure L or Z for 22 to 28 weeks. Ophthalmoscopically visible lesion areas were plotted as a function of exposure energy, with greater slopes of the regression lines indicating greater sensitivity to damage.

Results: In control animals, the fovea was less sensitive to blue-light-induced damage than the parafovea. Foveal protection was absent in xanthophyll-free animals but was evident after supplementation. In the parafovea, animals low in n-3 fatty acids showed greater sensitivity to damage than animals with adequate levels.

Conclusions: After long-term xanthophyll deficiency, L or Z supplementation protected the fovea from blue light-induced damage, whereas adequate n-3 fatty acid levels reduced the damage in the parafovea.

Figure 1.

Color photograph of the ocular fundus showing lesions (white spots) induced by blue-light exposures. There were two series of increasing energy with five exposures in each series. One series formed an inner arc of spots in the fovea at the edge of the macular pigment peak, whereas the outer arc of spots were in the parafovea in an area where macular pigment was optically undetectable. Lesions in the inner arc were smaller and there was no lesion at the location where the lowest energy was delivered. This image is from a control monkey with typical macular pigment.

Figure 2.

Lesion area as a function of exposure energy. Each data point is the area of a single lesion measured on the fundus photographs. Regression lines were computed from the GEE analyses. Slopes of the lines and P-values for comparisons are summarized in Tables 2 and 3. (A) Foveal and parafoveal lesion areas of control animals with typical laboratory diets and typical macular pigment densities. The fovea is less sensitive to blue-light exposure than the parafovea. (B) Foveal and parafoveal lesion areas of xanthophyll-free animals, with points for low-n–3 and adequate-n–3 animals plotted separately. Unlike the controls, the sensitivity of the fovea and parafovea were not significantly different within each fatty acid group. (C) Foveal lesion areas of xanthophyll-free animals before and after supplementation with lutein or zeaxanthin, compared with foveal lesions of control animals. Before supplementation, foveas of the xanthophyll-free animals were more sensitive to blue-light exposure than were the controls, but after supplementation they were not different from the controls. Regression lines for the other groups are repeated from (A) and (B), and therefore only data points for the supplemented animals are shown. Supplementation had no effect on the parafovea (data not shown). (D) Regression lines from (A) and (B) for parafoveal lesion areas of xanthophyll-free animals and controls plotted together for comparison. Again, the individual data points are shown in (A) and (B) and are not repeated here. Animals fed diets with adequate amounts of n–3 fatty acids were not different from the controls, but the parafoveal regions of animals fed low amounts of n–3 fatty acids were more sensitive to blue-light exposure than were the controls.