(NBC News) Google "marijuana glaucoma" and you'll find gobs of information claiming cannabis treats the eye condition.
But what's real, and what's not?
Glaucoma expert Dr. Dana tannenbaum hears the rumor all the time.
"I probably get asked about marijuana once a week," she says.
Anecdotes have been going around for years that smoking marijuana can treat glaucoma. There is some truth to that.
Dr. Tannenbaum says cannabis can lower the eye pressure associated with the condition, but the effect is temporary.
"Someone would need to smoke, ingest or use marijuana pretty much every three to four hours in order to maintain that pressure lowering effect," she explains.
Glaucoma occurs when there's too much pressure in the eye.
Over time, that added pressure can damage the optic nerve and lead to vision loss.
That's exactly what patient Stephanie Norman is trying to prevent. She's heard the marijuana claim, too, but remains wary.
"I don't know how true that is, and I don't care to find out," she says.
Experts want to find out more about pot's potential to treat glaucoma.
"We could potentially utilize the chemicals in marijuana to actually make a safe, well-tolerated drug without side effects," Dr. Tannenbaum says.
Because marijuana is classified as a Schedule 1 drug, like heroin, doctors cannot do the research.
For now glaucoma is often successfully treated with special eye drops, lasers or surgery.