Schalch W. Carotenoids in the retina - a review of their possible role in preventing or limiting damage caused by light and oxygen. In: Emerit I, Chance B, eds. Free radicals and aging. Basel: Birkhäuser, 1992; v. 62.

Content: First review explaining the mechanistic role of Lutein and Zeaxanthin can have in risk reduction of eye diseases. The review shows that there is enough circumstantial evidence for a protective role of carotenoids in the retina to justify further research.

Schalch W. Importance of the carotenoids lutein and zeaxanthin for the human eye Part 1. Chimica Oggi - chemistry today 2001;19(9):12-5. Schalch W. Importance of the carotenoids lutein and zeaxanthin for the human eye Part 2. Chimica Oggi - chemistry today 2001;19(10):43-5.

Content: Part I and II: In the centre of the retina, where visual acuity is highest, a yellow spot called the macula (macula lutea) is visible. Its yellow colour is due to the high levels of the nutritional carotenoids lutein and zeaxanthin, which are specifically accumulated there more than in any other tissue. The centre of the macula contains relatively more zeaxanthin, while lutein predominates in the peripheral zone, as in the plasma. The physiological explanation for this selective accumulation is primarily based on filtration of potentially damaging blue light and quenching of photochemicallyinduced reactive oxygen species. It is believed that by these mechanisms lutein and zeaxanthin can contribute to reducing the risk of age-related macular degeneration (AMD), the leading cause of irreversible loss of vision in ageing Western populations. This is supported by epidemiological studies indicating that elevated dietary intakes and high blood concentrations of lutein and zeaxanthin are correlated with a reduction in the risk for this disease. Furthermore, intake of these carotenoids, either with food or through supplements, can specifically increase their levels in the macula. Pending the results of further experimental, epidemiological and, most importantly, well-controlled clinical intervention trials, lutein and zeaxanthin already now appear to be valid candidates as ingredients for food intended to maintain retinal function.

Stringham JM, Hammond BRJ. Dietary lutein and zeaxanthin: possible effects on visual function. Nutr Rev. 2005;63(2):59-64.

Content: Specific review on the effects of the macular pigment on visual performance. Shows why lutein and zeaxanthin are uniquely concentrated in ocular tissues.

Schalch W, Dayhaw-Barker P, Barker FM. The carotenoids of the human retina. In: Taylor A, ed. Nutritional and environmental influences on the eye. Boca Raton: CRC, 1999.

Content: Major review

Beatty S, Koh H, Phil M, et al. The role of oxidative stress in the pathogenesis of age-related macular degeneration. Survey of Ophthalmology 2000;45(2):115-34.

Content: Review of antioxidative mechanisms for AMD. The paper reviews the concept that AMD can be attributed to cumulative oxidative stress but concludes that the hypothesis is still unproven.

Bone RA, Landrum JT, Guerra LH, Ruiz CA. Lutein and zeaxanthin dietary supplements raise macular pigment density and serum concentrations of these carotenoids in humans. J. Nutr. 2003;133(4):992-8.

Content: Compasison of own data. In this study, the effects of a range of lutein doses (2.4- 30 mg/d), as well as a high zeaxanthin dose (30 mg/d), on serum and macular pigment were compared in a series of experiments. The rate of increase in macular pigment optical density was correlated with the plasma plateau concentration reached in the serum, but not with the pre-supplementation optical density.

Krinsky NI, Landrum JT, Bone RA. Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye. Annu Rev Nutr. 2003;23:171-201.

Content: Review of mechanistic basis of Lutein and Zeaxanthin in eye health. The paper suggested that increasing intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, but stated that a causative relationship has yet to be experimentally demonstrated.

Beatty S, Nolan J, Kavanagh H, O'Donovan O. Macular pigment optical density and its relationship with serum and dietary levels of lutein and zeaxanthin. Arch. Biochem. Biophys. 2004;430(1):70-6.

Content: Review on observational evidence that the onset of age-related maculopathy could be delayed, or even averted, with the antioxidant supplements Lutein and zeaxanthin.