Herb rosemary promotes eye health, may prevent macular degeneration LA JOLLA, Calif., Nov. 28 (UPI) -- A substance in rosemary may have clinical applications for diseases affecting the retina, including age-related macular degeneration, U.S. researchers say. Dr. Stuart A. Lipton and colleagues at Sanford-Burnham Medical Research Institute said carnosic acid, a component of the herb rosemary, promotes eye health. Specifically, Lipton's team found carnosic acid protected retinas from degeneration and toxicity in cell culture and in rodent models of light-induced retinal damage. Age-related macular degeneration, the most common eye disease in the United States, is a leading cause of blindness. A few year's ago, Lipton's team discovered carnosic acid fights off free radical damage in the brain. In the current study, Lipton, Tayebeh Rezaie and Takumi Satoh exposed the cells growing in the dish to hydrogen peroxide in order to induce oxidative stress, a factor thought to contribute to disease progression in eye conditions such as macular degeneration and retinitis pigmentosa. They found cells treated with carnosic acid triggered antioxidant enzyme production in the cells, which in turn lowered levels of reactive oxygen and nitrogen species -- cell-damaging free radicals and peroxides. Lipton, Rezaie, Satoh and colleagues tested carnosic acid in an animal model of light-induced damage to photoreceptors -- the part of the eye that converts light to electrical signals, enabling visual perception. The study, published in the journal Investigative Ophthalmology & Visual Science, found the rodents pre-treated with carnosic acid retained a thicker outer nuclear layer in the eye, indicating that their photoreceptors were protected.