Glaucoma is a group of eye disorders that can damage the optic nerve. Most cases of glaucoma result from increased pressure in the eye, called ocular hypertension. If untreated or not properly controlled, this intraocular pressure increase can result in peripheral vision loss and eventually blindness.
The mainstay of glaucoma treatment is medication in the form of eye drops, laser surgery and conventional surgery. For many people these treatments are successful, however, there are some patients who are treatment resistant.
Multiple studies show that THC lowers intraocular pressure via the Type 1 cannabinoid receptor.1,2,3,4 In one particular study, 5mg of THC was found to transiently lower intraocular pressure, with effects lasting only four hours, while CBD and a placebo did not lower the pressure.5
In 2002, the Research Advisory Panel of California instituted the Cannabis Therapeutic Research Program to permit cannabis use on a compassionate basis while data was collected for research. Nine patients with glaucoma were enrolled to evaluate the effectiveness of THC on eye pressure. No conclusive results were obtained, except that after an initial lowering of eye pressure in four of the nine patients, the decreases were not sustained and all patients elected to stop treatment. The authors concluded that, “development of tolerance and significant systemic toxicity appears to limit the usefulness of this potential treatment.”
I do not advocate the use of THC-rich cannabis as single drug therapy for glaucoma unless all other treatments have failed. I have a number of patients in my practice who find that the addition of THC-rich cannabis to their current glaucoma treatment has been beneficial, but I encourage these patients to stay on their vision-saving medications or to talk with their ophthalmologists about surgery if medications fail.
There are a number of mechanisms by which the optic nerve is damaged in glaucoma, including glutamate toxicity (glutamate is a neurotransmitter that is toxic when it accumulates) and inflammation. Both THC and CBD are well known neuroprotectants and have been shown to protect the optic nerve in experimental models of optic nerve crush injury,6 glaucoma7 and immune-mediated toxicity.8 Based on these promising findings, I encourage my patients with glaucoma to include CBD-rich cannabis in their regimen to help prevent optic nerve damage.
Hepler, Robert S., and Ira R. Frank. “Marihuana smoking and intraocular pressure.” Jama 217.10 (1971): 1392-1392.
Lockhart, Albert B., Manley E. West, and Henry IC Lowe. “The potential use of Cannabis sativa in ophthalmology.” West Indian med. j 26.2 (1977): 66-70.
Merritt, John C., et al. “Effect of marihuana on intraocular and blood pressure in glaucoma.” Ophthalmology 87.3 (1980): 222-228.
Porcella, Anna, et al. “The synthetic cannabinoid WIN55212‐2 decreases the intraocular pressure in human glaucoma resistant to conventional therapies.” European Journal of Neuroscience 13.2 (2001): 409-412.
Tomida, Ileana, et al. “Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study.” Journal of glaucoma 15.5 (2006): 349-353.
Yoles, E, et al. “HU-211, a nonpsychotropic cannabinoid, produces short-and long-term neuroprotection after optic nerve axotomy.” Journal of neurotrauma 13.1 (1996): 49-57.
El-Remessy, Azza B., et al. “Neuroprotective effect of (−) Δ 9-tetrahydrocannabinol and cannabidiol in N-methyl-d-aspartate-induced retinal neurotoxicity: involvement of peroxynitrite.” The American journal of pathology 163.5 (2003): 1997-2008.
Mecha, Miriam, et al. “Cannabidiol protects oligodendrocyte progenitor cells from inflammation-induced apoptosis by attenuating endoplasmic reticulum stress.” Cell death & disease 3.6 (2012): e331.