The condition of glaucoma is marked by high pressure of fluid within the eye, and it is the leading cause of blindness.
Glaucoma is treatable, and marijuana has supported this treatment for many patients.
This article will cover the scientific evidence for this therapeutic application as well as common dosages.
As always, we encourage you to speak to your doctor or a qualified health care practitioner before attempting to medicate with medical marijuana. The risks of glaucoma are too high to take an experimental approach to treatment.
Medical Cannabis & Glaucoma
Glaucoma is a condition that affects 250,000 Canadians.
There are two types of glaucoma: open-angle glaucoma and acute angle-closure glaucoma.
Open-angle glaucoma is the most common, and there are no obvious warnings or symptoms in the people who contract it. Gradual loss of vision is the main indicator of the condition.
Left untreated, it can lead to permanent blindness.
The condition is characterized by a buildup of fluid in the eyes called aqueous humor. This fluid flows throughout the eye, but it can create harmful pressure when it does not drain correctly or is produced in surplus.
Treating glaucoma with marijuana is a more natural route than many of the pharmaceutical eye drops and medications available.
Studies have observed that marijuana does indeed reduce the pressure caused by buildup of aqueous humor through a number of mechanisms.
A 1980 study of 18 glaucoma patients showed that the ability of weed to lower blood pressure may be related to its mechanism of action for glaucoma (Merritt et al. 1980).
Marijuana has vasodilation properties, which means it can it assist blood vessels in dilating and diminish blood pressure. In this study, subjects who inhaled cannabis showed decreases in IOP that followed from decreases in blood pressure.
Cannabinoids & Glaucoma
The science surrounding glaucoma and marijuana rests to a large degree on compounds called cannabinoids and the effects they have on the body.
Tetrahydrocannabinol, or THC, is perhaps the most well-known cannabinoid as it is the source of marijuana’s euphoric and mood-altering effects.
Interestingly, a lot of the research examining the IOP-mitigating effects of THC looked at applications directly to the eye. Applying cannabinoids to the eye does not produce psychoactive effects.
THC has been observed to significantly mitigate intraocular pressure in animal studies where the cannabinoid was applied directly to the eye. Rabbit glaucoma models showed IOP-lowering activity when applied topically to the eyes in a 2017 study (Adelli et al. 2017).
In another similar 2008 animal study, synthetic THC administered to rat glaucoma models saw considerable decreases in intraocular pressure with no negative effects on blood pressure or heart rate (Oltmanns et al. 2008).
If you are looking for marijuana eye drops for glaucoma in Canada, these have not yet been made available by licensed producers. Speak to a doctor or licensed health care practitioner before attempting to apply cannabinoids in any form to your eyes.
CBG, or cannabigerol, is a non-psychoactive cannabinoid that has also been researched in terms of its treatment potential for glaucoma.
In a 2009 animal study, CBG was applied to the eyes through a sophisticated minipump and a connecting device called an extraocular cannulas. THC was also applied this way unilaterally from CBG.
While neither cannabinoid produced declines in aqueous humor formation, they both increased the rate of drainage two- to three-fold (Colasanti 2009). CBG is therefore also considered to be a significant naturally occurring compound in cannabis for the treatment of this condition.
CBD & Glaucoma
What about CBD-dominant cannabis oil for glaucoma ?
Cannabidiol (CBD) is a non-psychoactive cannabinoid that factors into cannabis-based treatments for anxiety, multiple sclerosis and epilepsy, to a name a few.
But is it effective for treating glaucoma?
One double-blind, randomized human study published in 2006 showed that 20 mg of CBD did not produce declines in intraocular pressure, and 40 mg of CBD actually generated temporary rises in IOP (Tomida et al. 2006).
CBD is neuroprotective, and the study proposed that while it does not impact IOP it may defend retinal nerve cells from harm caused by intraocular pressure.
However, these effects require more research.
How Does Marijuana Help Glaucoma?
Endocannabinoid receptors in the eyes are largely what make treating glaucoma with cannabis effective.
The endocannabinoid system is made up of interconnected receptors spread throughout the body’s systems and tissues. This system affects virtually every physiological process in the body, including appetite, pain regulation, mood regulation and immune function.
The eye structures contain CB1 and CB2 receptors which modulate the production and outflow of aqueous humor. The proposed mechanism of action by which THC helps relieve buildups in the eye is through activating these receptors.
Marijuana Dosage for Glaucoma
20 milligrams of THC per day, taken in 4 separate doses spread throughout the day through inhalation, ingestion or sublingually, has been observed to relieve intraocular pressure.
This dosage is not a standardized guideline and is for information purposes only.
Before attempting to self-medicate with cannabis for a potentially life-altering condition like glaucoma, we recommend you seek the advice of a licensed ophthalmologist who understands herbal cannabis dosages.
Short-term lowering of intraocular pressure is an effect of cannabis that has been demonstrated in multiple studies.
At this time, cannabis is normally prescribed as an adjunct therapy for glaucoma patients. Innovative delivery methods are being researched to better target the receptors in the eye.
Before you make a decision about medical cannabis and glaucoma, it is best to discuss your options with your physician or another knowledgable health care practitioner so you can determine how marijuana will best fit into your therapy.
- Adelli, Goutham R., Prakash Bhagav, Pranjal Taskar, Tushar Hingorani, Sara Pettaway, Waseem Gul, Mahmoud A. ElSohly, Michael A. Repka, and Soumyajit Majumdar. “Development of a Δ9-Tetrahydrocannabinol Amino Acid-Dicarboxylate Prodrug With Improved Ocular Bioavailability.” Investigative ophthalmology & visual science 58, no. 4 (2017): 2167-2179.
- COLASANTI, BRENDA K. “A comparison of the ocular and central effects of Δ9-tetrahydrocannabinol and cannabigerol.” Journal of Ocular Pharmacology and Therapeutics 6, no. 4 (1990): 259-269.
- Merritt, John C., William J. Crawford, Paul C. Alexander, Alfred L. Anduze, and Solomon S. Gelbart. “Effect of marihuana on intraocular and blood pressure in glaucoma.” Ophthalmology 87, no. 3 (1980): 222-228.
- Oltmanns, Matt H., Sandeep S. Samudre, Ivan G. Castillo, Alireza Hosseini, Aron H. Lichtman, Robert C. Allen, Frank A. Lattanzio, and Patricia B. Williams. “Topical WIN55212-2 alleviates intraocular hypertension in rats through a CB1 receptor mediated mechanism of action.” Journal of Ocular Pharmacology and Therapeutics 24, no. 1 (2008): 104-115.
- Tomida, Ileana, Augusto Azuara-Blanco, Heather House, Maggie Flint, Roger G. Pertwee, and Philip J. Robson. “Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study.” Journal of glaucoma 15, no. 5 (2006): 349-353.
- Wallace, Mark, Gery Schulteis, J. Hampton Atkinson, Tanya Wolfson, Deborah Lazzaretto, Heather Bentley, Ben Gouaux, and Ian Abramson. “Dose-dependent effects of smoked cannabis on capsaicin-induced pain and hyperalgesia in healthy volunteers.” The Journal of the American Society of Anesthesiologists 107, no. 5 (2007): 785-796.
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