Non-invasive optical techniques for the measurement of macular pigments

Abstract

Clinical studies of carotenoid macular pigments (MP) and chronic retina disease have been limited by the lack of non-invasive, objective techniques. In this paper we describe anovel, noninvasive optical techniques based on the resonant Raman spectroscopy for the assessment of the carotenoid status of human retina in vivo. Using resonant excitation in the visible, we measure the Raman signals that originate from the single- and double-bond stretch vibrations of the π-conjugated carotenoid molecule's carbon backbone. MP Raman detector, robust device useful for routine measurements of MP concentration in a clinical setting, has been developed and tested in clinical studies in humans to validate its function and to begin to establish its role as a possible screening test for macular pathologies. We report our first results on using carotenoid Raman detection in imaging mode. The results on retinal Raman imaging reveal highly specific and quantitative information regarding the spatial distribution of macular pigments. We also compare Raman technology with others availabe today subjective and objective MP detection methods and show that Raman spectroscopic technology has tremendous potential as a breakthrough method for rapid screening of carotenoid antioxidant levels in large populations that are at risk for vision loss from age-related macular degeneration, the leading cause of blindness of the elderly in the developed world.