Raman imaging of human macular pigments

Abstract

We have expanded our efforts to generate high spatial resolution images showing the distibution of carotenoid macular pigments in the human retina using Raman spectroscopy. A low level of macular pigments is associated with an increased risk of developing age-related macular degeneration, a leading cause of irreversible blindness. Using excised human eyecups and resonant excitation of the pigment molecules with narrow bandwidth blue light from a filtered arc lamp, we record Raman images originating from the carbon-carbon double bond stretch vibrations of lutein and zeaxanthin, the carotenoids comprising human macular pigments. Our Raman images reveal significnt differences among subjects, both in regard to absolute levels ss well as spatial distribution within the macula. Since the light levels used to obtain these images are well below established ssafety limits, this technique holds promise for developing a rapid screening diagnostic in large populations at risk for vision loss from age-realted macular degeneration.