Can Marijuana Treat Glaucoma? What You Should Know Before Taking Cannabis for Glaucoma

Cannabis (marijuana) can help treat several medical conditions. For almost 50 years, researchers have been studying whether cannabis can treat glaucoma.

Glaucoma is a group of eye conditions that damage the optic nerve, which sends signals from the eye to the brain. Damage to the optic nerve leads to permanent vision loss. Some people with glaucoma have high pressure inside their eyes. This causes optic nerve damage.

Early research showed that cannabis can lower eye pressure. But newer studies have lessened the promise of cannabis for glaucoma treatment. If you have glaucoma and are trying to decide whether to try cannabis, here’s what you need to know about cannabis and glaucoma.

Can cannabis treat glaucoma?

No. Experts at the American Academy of Ophthalmology and the American Glaucoma Society do not recommend cannabis for glaucoma treatment. These experts cite studies showing that cannabis treatment is unreliable and comes with many side effects.

But even with this clear advice, many sources still showcase cannabis as a treatment for glaucoma. So where did this idea come from?

High pressure inside the eye causes some types of glaucoma. Early studies showed that smoking cannabis lowered pressure inside the eye by up to 30%. This led experts to look into whether it could treat glaucoma.

Roadblocks popped up right away.

Cannabis didn’t work for everyone. Only about 60% of people had lower pressure inside the eye after inhaling cannabis. And even then, the effect only lasted 3 to 4 hours.

Eye pressure needs to stay normal throughout the day and night to prevent vision loss. To control eye pressure 24 hours a day, people need to inhale a lot of cannabis. Studies estimate that you would need 18 mg to 20 mg of THC (tetrahydrocannabinol) at least 6 times per day.

Taking this amount of THC every day isn’t practical. And smoking or vaping this much cannabis would also harm the lungs and increase the risk of developing lung cancer. Inhaled cannabis is also expensive. Experts estimate that on average people would spend about $700 each month.

Researchers looked at whether cannabinoid eye drops could be a safer alternative. While these eye drops lowered pressure inside the eye, the effect didn’t last long. And to get picked up by the eye, the cannabinoids had to be dissolved in mineral oil. This made the eye drops too irritating for most people. Newer cannabis eye drops are dissolved in different oils that are less irritating. But these eye drops are still being studied and aren’t available yet.

In the 1970s, cannabis was a good option compared to other available glaucoma treatments. But that’s no longer the case. Today, glaucoma eye drops are affordable and reliable, and they cause fewer side effects. Plus, people only need to use them between one to three times per day.

Can cannabis make glaucoma worse?

It’s unclear. Cannabis may worsen glaucoma. This is another reason that experts don’t recommend using it.

Cannabis lowers blood pressure in the eye and lessens blood flow to the optic nerve. Less blood flow can cause more optic nerve damage and worsen glaucoma. 

It’s not clear if there’s a dose of cannabis that can lower eye pressure without lowering blood flow to the optic nerve. So experts can’t offer guidance on how much cannabis people can safely take if they have glaucoma. 

Does marijuana help glaucoma?

There’s not a lot of solid evidence that taking cannabis helps glaucoma. But this may change as more research becomes available.

There’s evidence that cannabis may promote fluid movement inside the eye. There’s also some evidence that cannabinoids have antioxidant properties that can help protect the optic nerve. But researchers are quick to point out that these things have only been shown during lab experiments and not in humans.

These findings alone aren’t enough for experts to recommend cannabis as a treatment option for glaucoma. But if you're looking for a complementary treatment for glaucoma, talk to your ophthalmologist about whether cannabis is an option for you.

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Written by:

Nishika Reddy, MD

Nishika Reddy, MD, is an attending physician at the University of Utah. She provides comprehensive and cornea medical care at the Moran Eye Center and serves as clinical assistant professor.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

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