chapter  5
12 Pages

Quantitative Methods for the Determination of Carotenoids in the Retina

Acknowledgments ............................................................................................................................ 83 References ........................................................................................................................................ 83

A remarkable sequence of selective processes leads to the uptake of just two carotenoids by the primate eye. Approximately 750 naturally occurring carotenoids have been identi ed, some 30-50 of these are consumed as part of the human diet, and about 20 are found in the blood. Yet only the dihydroxy carotenoids, lutein and zeaxanthin undergo active uptake from the blood into various tissues in the eye. Of particular interest is the concentration of lutein and zeaxanthin in the center of the retina where they form a visible yellow spot, or “macula lutea” (Bone et al. 1985). The reason for such interest is the evidence that has been uncovered over the years for a protective function by this “macular pigment” (MP), in particular against the eye disease, age-related macular degeneration (AMD) (Schalch 2001). There are two potential modes of protection. The MP forms a blue-lightabsorbing layer in the inner part of the retina and reduces the amount of toxic blue light reaching the posterior tissues that tend to become damaged in AMD patients. Additionally these carotenoids possess antioxidant activity with the ability to quench reactive oxygen species and free radicals that could otherwise lead to damage (Beatty et al. 2000b).