Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world. The macula, the central part of the retina, is responsible for optimal spatial vision. There is a growing body of evidence that a lack of a dietary pigment at the macula, known as macular pigment (MP), is associated with increased risk of AMD.
MP contains the carotenoids lutein (L), zeaxanthin (Z) and meso-zeaxanthin (meso-Z). The typical western diet contains around 60 carotenoids, and 18 have been identified in human serum. However, only three are found at the macula, indicating the unique biological selectivity for their uptake at this location. The function of MP remains undetermined. It is likely that the accumulation of MP has evolved because of its optical and antioxidant properties; for example, MP limits retinal oxidative damage passively (through filtration of blue light) and actively (by quenching free radicals). Furthermore, its optical properties suggest a key role for MP in enhancing visual performance and supporting ‘super’ vision by reducing the effects of chromatic aberration and light scatter.
Recent research has shown that MP can be augmented by dietary supplementation in most (but not all) subjects, suggesting that the macular concentrations of these carotenoids are suboptimal in many people. My laboratory has discovered that a dip in the central portion of this pigment, seen in around 12% of individuals, is an undesirable feature of its spatial profile and may be linked to an inability to generate meso-Z at the macula. However, we have identified that enrichment of MP can be achieved by inclusion of meso-Z in a dietary supplement.
We propose to uniquely enrich MP and assess its impact on visual performance in normal subjects and visual function in patients with AMD. This groundbreaking study will advance our understanding of the protective and optical hypothesis of MP, and potentially improve normal vision and prevent or delay blindness due to AMD.
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