Glaucoma and medical marijuana: 5 informative facts

Glaucoma is the leading cause of blindness in people over 60

By Richard Faulk, 

What’s Glaucoma? Glaucoma is a gradual loss of vision caused by damage to the optic nerve. It comes in several varieties, but essentially the culprit is increased interocular pressure (IOP) caused by a build up of fluid in the eye. Glaucoma is the leading cause of blindness in people over 60.

What Is Medical Marijuana Glaucoma Treatment? The discovery of cannabis’s glaucoma-fighting power was happy accident in the War on Drugs. In the early 1970s, a group of UCLA researchers, led by Drs. Robert Hepler and Thomas Ungerleider, began studying the telltale marijuana “red eye” and pupil dilation in hopes of somehow using the phenomena to help the DEA to narc out stoners. The real takeaway, however, was something not at all expected: Cannabis—particularly the THC in cannabis—reduced eye pressure by 25 to 30 percent. That result was as good as any produced by an FDA-approved glaucoma medication. (In fact, it still is today.)

A topical treatment could be a way of sidestepping the intoxicating side effects of smoked or 
ingested cannabis. THC eyedrops have been tested, but there are practical hurdles to clear: 
THC dissolves best in alcohol or oil—neither of which is something you want to put in your eye.
iStock / Getty Images Plus

What’s the Catch? Unfortunately, the effect cannabis has on IOP lasts only about three hours, and THC, the element most responsible for pressure relief, is also the most psychoactively potent. To be completely treated, you’d need to smoke six or seven joints a day. In other words, you’d be high all the time. (On the other hand, you might not be very high: THC’s depressurizing effect is not dose dependent, so weak bud is as effective in this case as the stoniest in your arsenal.)

What Do the Pros Say? Neither the American Association of Ophthalmology, American Glaucoma Society, nor the Glaucoma Research Foundation endorses medical marijuana glaucoma treatment. This is partially because they view ridding a perpetual pot high as a less-than-optimal way of being in the world (squares!), but they also have a medical reason: Lowered blood flow can damage the optic nerve, and one of the side effects of cannabis is to lower blood pressure. Ironically, then, pot can both ease glaucoma and make it worse.

What’s Next? A topical treatment could be a way of sidestepping the intoxicating side effects of smoked or ingested cannabis. THC eyedrops have been tested, but there are practical hurdles to clear: THC dissolves best in alcohol or oil—neither of which is something you want to put in your eye.

Saline-based THC eye drops, at least at the moment, can’t deliver a powerful enough does. More troubling, topical THC can damage the surface of the eye. But this doesn’t mean that THC therapy is at an impasse, just that more research and testing is needed.

Bonus, Non-Glaucoma Factoid: Dr. Hepler’s team also found that cannabis suppresses tear production. While that’s bad news for wearers of contact lenses, one canny housewife reported that toking up was a prophylactic against that well known culinary malady: chopped-onion induced lachrymosity.