A composition of matter comprising a capsule or tablet, sized and designed for oral ingestion by a human, containing the 3R-3'R stercoisorner of zeaxanthin. The 3R-3'R stereoisomer of zeaxanthin constitutes at least about 90 percent of all zeaxanthin, while S-S and S-R stereoisomers constitute less than about 10 percent of all zeaxanthin in the capsule or tablet. The capsule or tablet contains a sufficient quantity of the 3R-3'R stereoisomer of zeaxanthin to cause a detectable increase in zeaxanthin concentration in retinal tissue, or at least about 0.5 milligrams. It can be concentrated into an oily fluid or prepared in a microencapsulated granular formulation. The zeaxanthin can also be added to various types of foods, such as margarine, dairy products, syrup, cookie dough, and meat preparations. When consumed, the zeaxanthin can help treat and prevent eye diseases including macular degeneration, a leading cause of vision loss.