Lutein, zeaxanthin, and the macular pigment.

The predominant carotenoids of the macular pigment are lutein, zeaxanthin, and meso-zeaxanthin. The regular distribution pattern of these carotenoids within the human macula indicates that their deposition is actively controlled in this tissue. The chemical, structural, and optical characteristics of these carotenoids are described. Evidence for the presence of minor carotenoids in the retina is cited. Studies of the dietary intake and serum levels of the xanthophylls are discussed. Increased macular carotenoid levels result from supplementation of humans with lutein and zeaxanthin. A functional role for the macular pigment in protection against light-induced retinal damage and age-related macular degeneration is discussed. Prospects for future research in the study of macular pigment require new initiatives that will probe more accurately into the localization of these carotenoids in the retina, identify possible transport proteins and mechanisms, and prove the veracity of the photoprotection hypothesis for the macular pigments.