If perception is reality, then it’s a good idea to know what people think about marijuana’s role in glaucoma therapy. A team of ophthalmologists and epidemiologists in Colorado, one of the many states that have legalized medicinal marijuana, set out to do exactly that, and what they found surprised them.
“Physicians are often too busy to spend enough time discussing these topics with patients,” said ophthalmologist and lead researcher Leonard K. Seibold, MD. “And patients are typically reluctant to bring it up with their doctor during their visit. However, if a patient went to a dispensary, we wanted to know what kind of advice or recommendation they might receive.
Survey: Can marijuana treat glaucoma?
To get the full picture, Dr. Seibold surveyed three groups: ophthalmologists specializing in glaucoma, patients with glaucoma and people who work at marijuana dispensaries to understand their perception of the role of marijuana in glaucoma treatment.
Even though marijuana use among adults has doubled in recent years, only 2.6% of Coloradans responding to the survey reported using marijuana for their glaucoma, a far lower rate than Dr. Seibold and his fellow researchers at the University of Colorado, Aurora had expected.
In stark contrast, more than half (51%) of the medical marijuana dispensaries recommended marijuana products for the treatment of glaucoma.
“In a state like Colorado, where marijuana is legal for both medicinal and recreational use, we were expecting a much higher rate,” Dr. Seibold said. “Our sample did consist of patients under the care of a glaucoma specialist, who only rarely recommends marijuana as a treatment. For the broader population, it is possible this rate may be higher.”
The perception among his fellow ophthalmologists who specialize in treating people with glaucoma was unsurprising. Of those who responded, only 7.6% reported that they had recommended marijuana for the treatment of glaucoma, and most of these ophthalmologists (86.4%) did so infrequently.
Why doctors don't support marijuana for glaucoma
Short answer: because it has some serious limitations and possible risks.
Marijuana has been promoted as a treatment for glaucoma since the 1970s after a few, limited studies showed that it could lower the pressure inside the eye. Glaucoma is often linked to a buildup of pressure inside the eye. The increased pressure inside the eye damages the optic nerve and can lead to blindness.
While it's true that smoking marijuana can reduce pressure inside the eye, it remains a suboptimal treatment because people with glaucoma require 24-hour pressure control to prevent vision loss. You would need to smoke marijuana eight to 10 times a day, every day. The potency of marijuana also varies considerably, and there's not enough research currently available to know the optimal dose for each patient or how it interacts with other medications.
CBD can make glaucoma worse
Then there are the side effects. Marijuana can cause the heart to beat faster and decrease blood pressure, which can reduce blood flow to an already compromised optic nerve. Smoking marijuana long-term may increase the risk of lung cancer. And one study showed that some people can build up a tolerance to marijuana's eye pressure-lowering effects. Another recent study showed that some compounds in marijuana like CBD may actually be harmful in glaucoma.
“My approach with patients is primarily to educate them on the very limited knowledge we have on the effects of marijuana on IOP and glaucoma,” Dr. Seibold said. “My favorite line to tell patients is that the most likely thing it will do is make you forget to take the eyedrops that I know will help.”
The bottom line: Glaucoma is best treated with prescription eyedrops
Dr. Seibold said he’s not against using marijuana as a treatment. But until a new therapy can show it works to consistently lower eye pressure with fewer side effects than the standard treatment of eyedrops, laser surgery or incisional surgery, he will continue to recommend patients stick with their prescribed therapy and come in for regular visits, so he can monitor their long-term care.
Until more research is done, the American Academy of Ophthalmology does not recommend marijuana or other cannabis products for the treatment of glaucoma. The American Glaucoma Society and the Canadian Ophthalmological Society agree.