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W. Gellermann, M. Sharifzadeh, P.S. Bernstein; Quantitative Imaging of Human Macular Pigment Distributions . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5666.
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To develop objective non–invasive optical technologies suitable to simultaneously image and quantify the spatial distributions of macular pigment, MP, in human subject populations.
We have used two optical spectroscopies in imaging modes to measure MP concentrations in the human retina and to simultaneously obtain micron–scale information about the topology of the MP distributions. Measurements were carried out on a clinical population involving more than 100 subjects free of macular pathologies. One of the methods, based on fluorescence originating from retinal chromophores ("autofluorescence"), was used to indirectly quantify and spatially image MP distributions via spatially varying attenuation of the fluorescence. The other method, based on Resonance Raman spectroscopy, was used to directly quantify and image the MP distributions by recording the spatially resolved Raman scattering responses from the C=C double bond stretch vibrations of the MP molecules (lutein and zeaxanthin). The instrumentation is based on blue/green solid state laser excitation sources and filtered CCD camera detection of the optical signals. Comparing MP levels between peripheral and foveal locations, the influence of media opacities is minimized. We validated our detection approaches by correlating optical MP measurements of excised retinas (eycups) with HPLC measurements.
For each subject, MP levels and distributions could be recorded within a fraction of a second without need for pupil dilation. The results, displayed as color–coded digital images (pixel intensity maps), allowed us to obtain spatially resolved MP levels, levels integrated over the whole MP distributions, and line plots along meridional lines. We found distinctly differing distribution patterns of MP in different individuals, including MP distributions that are predominantly concentrated in the foveola, distributions that are spatially extended further into the perifovea, and distributions with ring–shaped MP patterns. Integrated MP levels differ strongly between individuals.
Our studies show that autofluorescence based indirect detection and direct resonance Raman techniques are well suited for objective, quantitative, and rapid screening of macular pigment levels and their spatial distributions. Both techniques can be employed without need for pupil dilation. They hold promise as non–invasive optical diagnostics tools in large–scale clinical epidemiological and interventional studies of nutritional supplementation for the prevention of macular degeneration.
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