RAMAN DETECTION OF MACULAR CAROTENOID-PIGMENTS IN INTACT HUMAN RETINA

PURPOSE. TO develop and test a novel noninvasive optical technique sui table for the objective measurement of macular carotenoid levels in hu man retina. METHODS. A resonance Raman scattering apparatus was constr ucted to measure carotenoid levels in flat-mounted human retinas and e yecups and in experimental animal eyes. Light from an argon laser was used to resonantly excite the electronic absorption of the carotenoid pigments, and scattered light was collected and analyzed by a Raman sp ectrometer. After carotenoid Raman measurements were completed on the retinal samples, macular carotenoid levels were determined by highperf ormance Liquid chromatography (HPLC). RESULTS. Carotenoid resonance Ra man scattering proved to be a highly sensitive and specific method for the noninvasive measurement of macular pigments in the human retina. Signal strength scaled linearly with actual macular carotenoid content as measured by HPLC. Our apparatus was also used to record resonance Raman signals from xanthophyll carotenoids stored in the retinal pigme nt epithelium of intact frog eyes. CONCLUSIONS. This new noninvasive o ptical method will facilitate studies of ocular carotenoid distributio ns and their role in degenerative diseases of the eye and map allow fo r the rapid screening of carotenoid levels in large populations at ris k for vision loss from age-related macular degeneration, the leading c ause of blindness in the elderly in the United States. A prototype cli nical instrument is under development.