How Cannabis Can Treat Glaucoma
Glaucoma is a condition characterized by increased pressure within the eye. This can cause damage to the blood vessels and nerve endings that carry impulses to the optic nerve, which can impair vision. If this is a chronic type of glaucoma(open-angle glaucoma) and pressure is slowly increased over time, there can be peripheral vision loss and problems seeing in the dark. If it is acute (closed-angle glaucoma) the pupil may become dilated and fixed and immediate medical attention is required. The incidence of glaucoma increases with age and has a genetic predisposition. It is usually treated with medicated eye drops.
Some Eye-Opening Results
NOTE FOR FIRST TIME READERS: Cannabinoids – such as tetrahydrocannabinol (THC), CBD – and terpenes are the main medically active components in cannabis (aka marijuana). For more information on these components, and much more about the plant, see our section on the Science of Cannabis.
It was first observed that cannabis reduces intraocular pressure during a 1971 systematic investigation on healthy cannabis users. It was found that some derivatives of cannabis lowered the intraocular pressure (IOP) when taken intravenously, by smoking or orally, but not when applied topically to the eye.
Because it was thought that constant inhalation of cannabis as often as every three hours was required, it was not recommended to use cannabis to treat glaucoma as the ensuing side effects significantly outweighed the benefits.
Cannabis decreases IOP by an average 25-30%, occasionally up to 50%. Some non-psychotropic cannabinoids, and to a lesser extent, some non-cannabinoid constituents of the hemp plant also decreases pressure. The specific mechanism in cannabis that causes this is not known.
Cannabis treatments for glaucoma have mostly been in combination with eye drops, as the effects seem to be additive. A non-psychoactive extract of cannabis was tested in combination with Timolol eye-drops in glaucoma patients with high IOP in 1980. They found that the effects of the two medications were complementary and were beneficial in some cases where other medications had failed. More testing needs to be done to determine how and when cannabinoids are indicated in the treatment of glaucoma.
With patients who use cannabis to treat glaucoma, it’s been shown that chronic use does not have to be administered every 3 hours for long-lasting eye pressure reduction. But THC does seem to be more effective than CBD.
A topical preparation of cannabis has not been pharmaceutically available, but this approach is promising. A single topical application of THC lowered IOP substantially (~28%) for 8 hours in male mice.
Ingestion or Smoking: Which is Better?
In general, a 10 mg dose of THC one to two times/day might be required for eye pressure reduction. This can be delivered as THC-rich cannabis, or mixed with CBD to decrease psychoactivity, as in a CBD/THC 1:1 mix.
Some choose to take most of their THC before bed, so it acts when you sleep, i.e. 10 mg, and then use a low dose of the mix one to two times per day. This can be done with edibles, tinctures, or capsules.
For those who want to use marijuana cigarettes or vaporize, it should be done at least 4 times a day to reach sufficient THC levels. THC in eye drop formulation would be fantastic but is not currently available.
- Crandall J, et al. Neuroprotective and intraocular pressure-lowering effects of (−)Delta9-tetrahydrocannabinol in a rat model of glaucoma. Ophthalmic Research. 2007, 39: 69–75.
- Hepler RS, Frank IR. Marihuana smoking and intraocular pressure. Journal of the American Medical Association. 1971, 217: 1392.
- Kaufman PL. Marijuana and glaucoma. Archives of Ophthalmology. 1998, 116: 1512-3.
- Miller S, Daily L, Leishman E, Bradshaw H, Straiker A. D9-tetrahydrocannabinol and cannabidiol differentially regulate intraocular pressure. Investigative Ophthalmology and Visual Science. 2018, 59(15): 5904-5911.
- Tomida I, Pertwee RG, Azuara-Blanco A. Cannabinoids and glaucoma. British Journal of Ophthalmology. 2004, 88(5): 708-713.
- Tomida I, et al. Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study. Journal of Glaucoma. 2006, 15(5): 349-53.