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M. L. Kirby, E. Loane, S. Beatty, J. Stack, J. M. Nolan, Macular Pigment Research Group; Reproducibility of the Spatial Profile of Macular Pigment. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4959.
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© ARVO (1962-2015); The Authors (2016-present)
Macular pigment (MP) is composed of the dietary carotenoids lutein, zeaxanthin and meso-zeaxanthin. The spatial profile of MP has been described as exponential, as it peaks at the foveal centre, and decreases with increasing eccentricity from the fovea. There is, however, evidence to suggest that some individuals have a secondary peak at roughly 0.7 degrees of eccentricity. For such individuals, their MP profile has been described as "tri-modal". This study was designed to investigate the reliability and reproducibility of the MP spatial profile within each subject, using a customised version of heterochromatic flicker photometry (cHFP).
We recruited twenty healthy subjects, selected as a nested sample from a large subject database [n= 300] (10 of whom were selected as they displayed a secondary peak in their MP spatial profile, and 10 of whom were selected as they displayed the normal exponential decline in their MP spatial profile). MP optical density (MPOD) spatial profile was measured on three separate occasions. On each of the three occasions, six radiance measurements were obtained, at 0.25°, 0.5°, 1°, and 1.75° of eccentricity.
Most subjects, displaying a secondary peak at visit one, still displayed a secondary peak after averaging repeated measures (see Fig 1.). Likewise, subjects who displayed the normal exponential decline profile at visit one, still displayed the normal exponential decline profile after averaging repeated measures (see Fig 1.)
The technique of cHFP provides a reproducible measurement of MP, and its spatial profile. Also, the secondary peak seen in some subjects cannot be attributed to measurement error of the cHFP method. Further data on a larger number of subjects will follow, and is required to pass further comment.
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