American Academy of Ophthalmology
Written By: David Turbert and Dan T. Gudgel
Reviewed By: Andrew George Iwach, MD
Jan. 28, 2019
Cannabis and currently available compounds derived from marijuana – like CBD – are not an adequate treatment for glaucoma, or any eye condition. To treat glaucoma, eye pressure must be managed 24 hours a day. Marijuana is not a practical treatment for constant use. And more research is still needed into the exact effects of cannabis and cannabis compounds on eye pressure and glaucoma.
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.
Several current, effective treatments for glaucoma are more reliable and safer than marijuana. If you have glaucoma, you should follow your ophthalmologist’s advice to get the treatment that’s right for you.
The bottom line about marijuana and glaucoma is:
The largest association of eye physicians and surgeons in the world does not endorse cannabis or its derivates as a glaucoma treatment.
Do not self-medicate with marijuana in an attempt to treat glaucoma. You can lose your vision if you don’t have a reliable, effective treatment for glaucoma.
Speak with your ophthalmologist to find the glaucoma treatment option that’s best for you.
Tell your doctor if you do use marijuana regularly.
What is the Connection Between Glaucoma and Marijuana?
Glaucoma is an eye condition in which the optic nerve becomes damaged over time, first reducing peripheral vision before possibly leading to total blindness. One cause of optic nerve damage in glaucoma is higher-than-normal eye pressure (intraocular pressure or IOP).
As marijuana has been legalized for medical or recreational use in more U.S. states and Canada, it has become more visible and discussed as a possible treatment for many health conditions. Research in the 1970s and 1980s did show a measurable decrease in intraocular pressure for three or four hours after smoking cannabis or ingesting THC as a pill or injection. But to treat glaucoma and save vision, eye pressure has to be controlled 24 hours a day.
To reduce intraocular pressure by 3 to 5 mm Hg — and maintain that reduction — you would have to ingest about 18 to 20 mg of THC six to eight times a day, every day. The possible negative effects on mood, mental clarity and (if smoked) lung health would be significant. You would not be able to drive, operate machinery or engage in many common activities. In addition, the cost of using marijuana every three to four hours, every day makes it cost-prohibitive for most patients.
As a comparison, alcohol also has a moderate intraocular pressure-lowering effect for an hour or so after a drink. But no doctor would recommend that you drink alcohol every hour to treat glaucoma. Many other effective treatments are available that don’t have the side-effects of alcohol.
Studies Haven’t Proven That THC is Effective or Reliable for Glaucoma Treatment
Studies have been done on THC eye drops, pills and cigarettes. Eye drops led to burning, irritated eyes and were shown to not lower eye pressure. A sublingual (placed in the mouth under the tongue) THC compound found no reduction in intraocular pressure. For another study, glaucoma patients were offered THC-containing pills and/or cigarettes. Within nine months all of them asked to stop due to side effects.
As scientists learn more about glaucoma, they have also come to understand that high intraocular pressure in the fluid at the front of the eye is not the only cause of optic nerve damage. Increasing evidence shows that reduced flow of blood to the optic nerve may also cause damage in patients with glaucoma. Marijuana not only lowers eye pressure, it also lowers blood pressure throughout the body. As a result, marijuana has the potential to lower the blood flow to the optic nerve, effectively canceling out the benefit of lowered intraocular pressure.
What About CBD for Glaucoma?
In recent years, CBD has received a lot of attention and scrutiny. CBD is a derivative of cannabis that doesn’t have mood-altering effects. But just like cannabis that’s smoked or eaten, there is no accepted, current research that shows CBD to be an effective treatment for glaucoma. In fact, one recent study showed that CBD may actually increase IOP, which would make glaucoma worse.
What is the Future of Marijuana for Glaucoma Treatment?
Currently, the only way to control glaucoma and prevent vision loss is to lower the pressure in your eye. Your ophthalmologist can treat glaucoma with medication, such as prescription eye drops, or surgery, depending on the type of glaucoma and how severe it is.
Scientists are exploring whether the active ingredients in marijuana may yet offer a glaucoma treatment. If the effects of cannabis compounds can be isolated, made to be long-acting, and the side effects eliminated, they may lead to new treatments in the future. However, such developments require more research and are years away from becoming a reality.