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Glaucoma is an eye disease where high intra-ocular pressure does permanent damage to the optic nerve and causes vision loss. Studies have shown marijuana decreases intraocular pressure.
Overview of Glaucoma
Glaucoma is an eye condition characterized by abnormally high pressure in the eye, which causes damage to the optic nerve. According to Mayo Clinic, glaucoma is one of the leading causes of blindness in the United States.
The vision loss caused by glaucoma cannot be recovered and the most common form of glaucoma has zero warning signs. The damage to the optic nerve is so gradual that most don’t notice the change in vision until the condition is at an advanced stage. Early detection through regular eye exams and a test that measures eye pressure, are necessary for glaucoma to be diagnosed early enough before permanent damage can be done. Those who are diagnosed with the condition will need regular treatment to lower eye pressure for the rest of their lives.
The elevated eye pressure is the result of a buildup of fluid called aqueous humor that flows throughout the eye. The fluid normally drains, but when it’s overproduced or doesn’t drain properly, pressure builds.
There are two types of glaucoma conditions, including open-angle glaucoma and acute angle-closure glaucoma. Open-angle glaucoma is the most common form of the condition. Acute angle-closure glaucoma can be accommodated with severe headache, eye pain, and nausea and vomiting.
Since glaucoma isn’t curable, treatment focus is on keeping the pressure lower in the eye through medications.
Findings: Effects of Cannabis on Glaucoma
Over multiple decades, scientific research has proven that cannabinoids are effective at decreasing intraocular pressure (Nadolska & Gos, 2008) (Pinar-Sueiro, Rodriguez-Puertas & Vecino, 2011). In addition, the compounds found in cannabis feature neuroprotection and vasodilation properties, which further assist in the conservative treatment of glaucoma (Nadolska & Gos, 2008) (Nucci, et al., 2008). The cannabinoids found in cannabis, including tetrahydrocannabinol (THC), activate endocannabinoid receptors CB1 and CB2 (Pinar-Sueiro, Rodriguez-Puertas & Vecino, 2011). The endocannabinoid receptors located in the structures of the eyes are responsible for the formation and outflow of aqueous humor (Nadolska & Gos, 2008) (Nucci, et al., 2008).
Smoking cannabis has demonstrated through numerous studies that it can be effective at lowering intraocular pressure. After inhaling THC, participants with open-angle glaucoma in one study had their blood and intra-ocular pressures decrease for three to four hours (Crawford & Merritt, 1979). Another study found that smoking marijuana lowered blood pressure, which led to a decrease in intra-ocular pressure within 60 to 90 minutes of inhalation (Merritt, et al., 1980). Yet another study found that glaucoma patients experienced a lowering of orthostatic blood pressure, but in just five minutes after smoking marijuana (Merritt, Cook & Davis, 1982).
For patients interested in avoiding the psychoactive effects of smoking cannabis, topical cannabinoid applications have also proven effective at decreasing ocular pressure (Jarvinen, Pate & Laine, 2002). In one study, applying THC oil directly to the eyes of participants with high blood pressure resulted in the lowering of systolic blood pressure, which researchers concluded may lead to a decrease in intra-ocular pressure (Merritt, Olsen, Armstrong & McKinnon, 1981). In another, applying cannabinoid directly to the eye decreased intraocular pressure within the first 30 minutes with maximal reduction being reached in 60 minutes (Porcella, Maxia, Gessa & Pani, 2001). One study that applied cannabinoids directly to the eyes of rabbits recorded decreased intra-ocular pressure within 1.5 hours of administration and the effects lasted for more than 6 hours. In addition, the eye to which the cannabinoid had not been administered also experienced a decrease in intra-ocular pressure, but the effect lasted for 4 hours (Naveh, et al., 2000).
States That Have Approved Medical Marijuana for Glaucoma
Currently, 26 states have approved medical marijuana for the treatment of glaucoma. These states include: Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Hawaii, Illinois, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Montana, Nevada, New Hampshire, New Jersey, New Mexico, North Dakota, Ohio, Pennsylvania, Oregon, Rhode Island, Vermont and Washington.
Several states have approved medical marijuana specifically to treat “chronic pain,” a symptom commonly associated with glaucoma. These states include: Alaska, Arizona, California, Colorado, Delaware, Hawaii, Maine, Maryland, Michigan, Montana, New Mexico, Ohio, Oregon, Pennsylvania, Rhode Island and Vermont. The states of Nevada, New Hampshire, North Dakota, Montana, Ohio and Vermont allow medical marijuana to treat “severe pain.” The states of Arkansas, Minnesota, Ohio, Pennsylvania and Washington have approved cannabis for the treatment of “intractable pain.”
In Washington D.C., any condition can be approved for medical marijuana as long as a DC-licensed physician recommends the treatment.
Recent Studies on Cannabis’ Effect on Glaucoma
Crawford, W.J., and Merritt, J.C. (1979, May). Effects of tetrahydrocannabinol on arterial and intraocular hypertension. International Journal of Clinical Pharmacology and Biopharmacy, 17(5), 191-6.
Facts About Glaucoma. (n.d.). National Eye Institute. Retrieved from https://nei.nih.gov/health/glaucoma/glaucoma_facts.
Glaucoma. (2015, September 15). Mayo Clinic. Retrieved from http://www.mayoclinic.org/diseases-conditions/glaucoma/basics/definition/con-20024042.
Jarvinen, T., Pate, D.W., and Laine, K. (2002, August). Cannabinoids in the treatment of glaucoma. Pharmacology & Therapeutics, 95(2), 203-20.
Merritt, J.C., Cook, C.E., Davis, K.H. (1982). Orthostatic hypotension after delta 9-tetrahydrocannabinol marihuana inhalation. Ophthalmic Research, 14(2), 124-8.
Merritt, J.C., Crawford, W.J., Alexander, P.C., Andruze, A.L., and Gelbart, S.S. (1980, March). Effect of marihuana on intraocular and blood pressure in glaucoma. Ophthalmology, 87(3), 222-8.
Merritt, J.C., Olsen, J.L., Armstrong, J.R., and McKinnon, S.M. (1981, January). Topical delta 9-tetrahydrocannabinol in hypertensive glaucomas. Journal of Pharmacy and Pharmacology, 33(1), 40-1.
Nadolska, K., and Gos., R. (2008). Possibilities of applying cannabinoids’ in the treatment of glaucoma. Klinika Oczna, 110(7-9), 314-7.
Naveh, N., Weissman, C., Muchtar, S., Benita, S., and Mechoulam, R. (2000, April). A submicron emulsion of HU-211, a synthetic cannabinoid, reduces intraocular pressure in rabbits. Graefe’s Archive for Clinical and Experimental Ophthalmology, 238(4), 334-8.
Nucci, C., Bari, M., Spano, A., Corasaniti, M., Bagetta, G., Maccarrone, M., and Morrone, L.A. (2008). Potential roles of (endo)cannabinoids in the treatment of glaucoma: from intraocular pressure control to neuroprotection. Progress in Brain Research, 173, 451-64.
Pinar-Sueiro, S., Rodriguez-Puertas, R., and Vecino, E. (2011, January). Cannabinoid applications in glaucoma. Archivos de la Sociedad Espanola de Oftalmologia, 86(1), 16-23.
Porecella, A., Maxia, C., Gessa, G.L., and Pani, L. (2001, January). The synthetic cannabinoid WIN55212-2 decreases the intraocular pressure in human glaucoma resistant to conventional therapies. European Journal of Neuroscience, 13(2), 409-12.
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