A new study finds marijuana is a relatively ineffective way to treat glaucoma

AUGUSTA, Georgia (CNN) -- A new study that says smoking marijuana is a hazy and impractical way to treat glaucoma is the latest twist to the medical marijuana debate.

The study, by ophthalmologist Keith Green at the Medical College of Georgia, found the medical benefits of smoking marijuana are slight and relief is temporary.

"Glaucoma is a 24-hour-a-day disease, 365 days-a-year disease and you cannot get away from it," he said.

The battle over legalizing marijuana for medical purposes has been smoldering for over 30 years. But the issue has been recently fueled by voters in five states --Alaska, Arizona, Oregon, Nevada and Washington -- who passed laws legalizing the drug to ease the symptoms of certain diseases such as glaucoma, AIDS and cancer.

Glaucoma is a chronic eye disease that can lead to blindness if left untreated. It is caused by an abnormal increase of fluid pressure in the eye which leads to the gradual loss of vision.

Researchers suspect a chemical in marijuana called tetrahydrocannabinol, or THC, can reduce interocular pressure which can prevent the disease from progressing.

But to be effective, Green said a patient would have to smoke an unrealistic amount of marijuana.

"If you want to maintain a low interocular pressure with marijuana, then you have to smoke a joint every 1 to 2 hours which is 10 to 12 joints a day, which is 4,000 a year," he said. "That's by anybody's definition -- no matter how liberal you are -- a considerable consumption."

His study is published in the recent issue of the American Medical Association's journal Opthamology.

Marijuana contains over 400 different chemicals, some of which cause a euphoric feeling that eliminates or lessons pain associated with many diseases.

But since glaucoma is a painless disease, some doctors feels the negative effects associated with smoking marijuana outweigh the known benefits, and patients would be better off using the available prescription medications until scientists can duplicate the effects of THC in a pill or topical ointment.

"For those who smoke cigarettes, marijuana has 50 percent more tar and volatile cancer-inducing compounds," Green said. "It causes emphysema, changes hormones, changes a whole bundle of things. It is quite a toxic chemical."

But advocates for medical marijuana say temporary relief is better than nothing.

"Should these patients suffer so?" said Allen St. Pierre, executive director of the National Organization to Reform Marijuana Laws Foundation.

Next month the Institute of Medicine plans to release its yearlong study on the medicinal benefits of marijuana use for many diseases, including glaucoma.

Food & Health Correspondent Holly Firfer and the Associated Press contributed to this report.

Food & Health Correspondent Holly Firfer and The Associated Press contributed to this report.