Chemist James Norris, Ph.D., and retina surgeon Kourous Rezai, M.D., combined resources to show that melanin, a pigment found throughout the human body, acts like a neutralizing sponge inside cells in the retina to soak up and destroy reactive oxygen species. Reactive oxygen species, or free radicals, energized by light, are thought to play a major role in macular degeneration, the leading cause of blindness in people over the age of 60.
"We now have the first persuasive evidence that melanin plays an important protective role within the eye," said Norris, professor in the Department of Chemistry and the Institute for Biophysical Dynamics at the University of Chicago and one of the senior authors of both papers. "Although melanin contains its own intrinsic free radical, we found that it absorbs a far more damaging form of free radical, converting its destructive energy into harmless heat before it can hurt the retina."
An estimated 1.75 million Americans have decreased vision from age-related macular degeneration (AMD), with about 200,000 new cases each year. The incidence of AMD is expected to double within the next 25 years as the number of older persons continues to increase. The disorder is far more prevalent among whites than among black persons.
It causes gradual loss of central vision by damaging the retinal pigment epithelial (RPE) cells that lie underneath the macula, the small region of the retina responsible for fine detail at the center of the field of vision. Without RPE cells, the photoreceptors, which are the light detectors, als
Contact: John Easton
University of Chicago Medical Center