Marijuana has been legalized for medical use in 30 US states and for recreational use in 9 US States. It is classified by the federal Drug Enforcement Agency as a Schedule I controlled substance (the same category as heroin and LSD). Nevertheless, perceptions and attitudes regarding marijuana use continue to evolve, with increasing interest in its therapeutic potential.
Ability to Lower Intraocular Pressure
Marijuana’s ability to lower intraocular pressure (IOP) was discovered in the 1970s. Elevated IOP is the major risk factor for glaucoma and lowering IOP is currently the only treatment. Doctors and scientists have wondered whether marijuana could be used as a therapy to lower IOP and prevent the progression of glaucoma. Glaucoma patients also are interested to know whether marijuana can be used to treat glaucoma.
While marijuana does lower IOP, it has major drawbacks as a treatment for a chronic, long-term, disease like glaucoma. First, in contrast to conventional glaucoma eyedrops (some of which are effective for up to 24 hours), smoking THC reduces eye pressure for only 3-4 hours. To control IOP would require 8-10 doses of marijuana per day. This would not only cost more than typical glaucoma treatment, but the physical and mental side-effects of frequent marijuana use would prevent functioning productively. For example, while users may enjoy its euphoric effects, marijuana also impairs judgment and coordination, increases paranoia, elevates heart rate, and irritates the eyes.
Long-term Safety Concerns
Concerns also exist regarding the long-term safety of marijuana use, due to its associations with permanent lung damage when smoked, and possible permanent adverse effects on cognition and mental health. With regular use, tolerance to the eye pressure-lowering effects develops, meaning that increasing drug levels would be required to prevent progression of glaucoma. Finally, lack of regulation and quality control makes efficacy and safety of marijuana unpredictable. Research efforts to develop THC eyedrops that can effectively lower eye pressure while minimizing side effects are underway but have not yet been successful.
For these reasons, while marijuana does lower eye pressure, it is not recommended as a medical treatment for glaucoma. If you use marijuana, let your eye doctor know since it may have an impact on your eye pressure readings. Also, it is very important to continue your current glaucoma therapy and regular monitoring as recommended by your eye doctor.
Article by Kathryn E. Bollinger, MD and Kevin M. Halenda, MD.
Posted on January 10, 2019.
Last reviewed on March 16, 2022.