Macular pigment: From discovery to function

An awareness of the presence of the “macula lutea” dates to a time during the last two decades of the eighteenth century, something more than two centuries ago (Nussbaum et al. 1981; Whitehead et al. 2006). Perhaps, it should be a surprise that fundamental facts needed to describe the macular pigments awaited discovery until the end of the twentieth century (Landrum and Bone 2001). A firm determination of the identities of the macular carotenoids, lutein and zeaxanthin, was established and confirmed during the mid-1980s providing the firm standing essential for further detailed research (Bone et al. 1985, 1988; Handelman et al. 1988). Since that time, the level of interest and enthusiasm that researchers have shown in the macular pigment has grown dramatically. The burgeoning enthusiasm underlying current research into the functional role of the macular pigments is also paralleled by an increasing interest that is now being devoted to the role of other non-vitamin A carotenoids. Bone et al. (1993) demonstrated that the rarely encountered carotenoid, mesozeaxanthin, comprises approximately 30% of the total macular pigment within the central fovea. The ability of carotenoids to act as antioxidants within the body is now widely recognized, and it is accepted that the retina is subject to high oxidative loads (Landrum 2013). The Age-Related Eye Disease Study I (AREDS I) demonstrated that antioxidant consumption significantly retards the progression of early stages of age-related macular degeneration (AMD) and the development of wet neovascular AMD (SanGiovanni et al. 2007). The possibility that the macular pigment has a role in the preservation of central vision among the increasing population of seniors is ample motivation for the intense scrutiny to which the macular carotenoids are now subject. In the United States, the Age-Related Eye Disease Study II (AREDS II), in which lutein and zeaxanthin are specific components, is approaching conclusion and continued research on the transport, localization, and actions of the carotenoids into the macula is certain to remain an important and productive line of investigation for the foreseeable future (Chew et al. 2012). The potentially broad importance of the non-provitamin A carotenoids in maintaining optimal human health also beckons researchers who are investigating the actions and role of carotenoids and their metabolites in cell functions.