Raman spectroscopy measures possible precursors of age-related blindness
Researchers at the University of Utah (Salt Lake City, UT) measured concentrations of carotenoid pigments in the human retina using resonance Raman spectroscopy. At CLEO `98 (San Francisco, CA), Werner Gellermann and colleagues reported that they found the concentration of the two pigments to be linearly proportional to the intensity of the Stokes lines. Two carotenoid pigments in the retina--lutein and zeaxanthin--are thought to protect the retina, both chemically as antioxidants and optically as filters that protect the rods and cones of the macula, from damage by higher-energy blue and violet photons. The carotenoids absorb light in the blue-green (emitted by an argon laser at 488 nm) and emit Stokes and anti-Stokes lines at 530 and 520 nm. Because the carotenoids do not fluoresce strongly, the resonant Raman lines can be seen clearly.
Age-related macular degeneration is a leading cause of blindness in older Americans, and studies have shown that there may be a link between such diseases and the presence or absence of the carotenoid molecules. Current methods for screening for early stages of macular degeneration are subjective. The researchers are now building a prototype device for measurements on living eyes and have received a National Institutes of Health grant for clinical testing.