The new study, the first documenting how the lens, retina and other eye tissues absorb these substances, opens the possibility that green tea may protect against glaucoma and other common eye diseases.

Glaucoma is a disease in which the optic nerve is damaged, leading to progressive, irreversible loss of vision.

Chi Pui Pang, department of ophthalmology and visual sciences, Chinese University of Hong Kong, and colleagues point out that the so-called green tea "catechins" have been among a number of antioxidants thought capable of protecting the eye.

Those include vitamin C, vitamin E, lutein and zeaxanthin. Until now, however, nobody knew if the catechins in green tea actually passed from the stomach and gastrointestinal tract into the tissues of the eye.

Pang and his colleagues resolved that uncertainty in experiments with lab rats that drank green tea, said a release of the American Chemcial Society (ACS).

Analysis of eye tissues showed beyond a doubt that eye structures absorbed significant amounts of individual catechins.

The effects of green tea catechins in reducing harmful oxidative stress in the eye lasted for up to 20 hours. "Our results indicate that green tea consumption could benefit the eye against oxidative stress," the study concludes.

These findings were published in the ACS bi-weekly Journal of Agricultural and Food Chemistry.