A deeper look required for role of antioxidants in eye disease

Antioxidants, such as the polyphenols found in green tea, have been championed for their protective value in cancerprotection. Their role in eye disease prevention, however, is still unclear. Dorairajan Balasubramanian, director ofresearch, L.V. Prasad Eye Institute, Hyderabad, India, reported on in vitro tests he has performed on cells and polyphenolssuch as epigallocatechin gallate (ECGC) and catechin, and their protective value against cytotoxic agents.

"These are very powerful antioxidants. They penetrate the cell membrane and protect the cells from DNA damage," Dr.Balasubramanian said. "We looked at their protective value in cataract formation, but lens replacement is basically so simplenow that the real question has become: Are the polyphenols in tea good for glaucoma?"

To find out, Dr. Balasubramanian examined retinal ganglion cells and stressed them using hydrogen peroxide. He found thatwhile various polyphenols did offer a protective effect to the retinal cells, some potentially brought their toxicity to thetable.

"For example, both catechin and EGCG protect the cells, but there is a toxicity to retinal cells associated with EGCG thatisn't associated with catechin," Dr. Balasubramanian said. He found the same protective-yet-toxic qualities in resveratrol,the antioxidant of red wine fame.

Other unanswered questions remain:

• Solubility in water. Does the systemically taken green tea molecule reach the eye? "Do you need to drink green tea for 40years for this to have an effect, or could eye drops provide a boost?" Dr. Balasubramanian asked. "What's the best mode toreach the proper concentration? That's an interesting question that still needs to be answered."
• What is the optimum dose for human eye protection?

Does the preparation of the tea itself affect the protective qualities of the antioxidants? Dr. Balasubramanian saidthat the sun drying of oolong tea changes the catechin on a molecular level, and the heat treatment of black tea gives it itscharacteristic color and flavor but adds molecules in the process.

"Is that good? We don't know," he said. "Should we all be drinking green tea as they do here in Hong Kong, or black tea as wedo in India?"