Noninvasive optical detection of carotenoid antioxidants in the human retina.

摘要

This dissertation develops laser Raman and fluorescence based spectroscopy for the noninvasive detection of medically important pigments in the human retina. Large-scale epidemiological studies have recently shown that the pigments lutein and zeaxanthin, located in the ∼1 mm diameter macular area of the retina, protect the eye from phototoxic blue light and/or oxidative damage.; Resonance Raman spectroscopy (RRS) can detect and monitor macular pigments in intact human eyes quantitatively by recording the Raman scattered light originating from the highly specific stretching vibrations of the pigment molecules' conjugated carbon backbone. This dissertation develops RRS from a spatially averaged measuring approach to spatially resolved imaging. For this purpose, a filter-based Raman imaging setup with speckle-free illumination was constructed that permits detection of macular pigments at physiological concentrations with eye-safe laser excitation levels. Subsequently, RRS images would be obtained from the living human retina. The images demonstrate quantitative as well as micron-scale, spatially resolved RRS detection of the whole macular pigment distribution. The RRS images reveal important physiological details of a subject's macular pigment distribution such as the peaked pigment concentration in the center of the macula, and the rapidly dropping pigment concentration towards the periphery of the macula.; As an alternative to direct RRS imaging of macular pigments, this dissertation explores an indirect imaging approach of macular pigments, based on excitation spectroscopy of lipofuscin. A dual-wavelength laser apparatus was constructed that excites the lipofuscin fluorescence at wavelengths inside and outside the spectral range of macular pigment absorption, and that allows one to image the fluorescence intensities in a large section of the retina centered on the macula. Measuring the lipofuscin fluorescence intensities inside and outside the macula area at the two wavelengths, respectively, results in pixel intensity maps which are used to quantify the macular pigment levels.; The results obtained to date show that optical imaging approaches are very promising, that they are well suited for clinical applications, and that they may well lead to a widely used, early screening technology of subjects based on a non-invasive, rapid, precise, and objective optical detection technology.