January is National Glaucoma Awareness Month: Exploring the history of medical marijuana therapy for glaucoma
Photo by Matt Dayak
Did you know that glaucoma is the second leading cause of blindness in the U.S.? A gradual loss of vision caused by damage to the optic nerve, it comes in several varieties. Essentially, the cause is increased intraocular pressure (IOP) caused by fluid buildup in the eye. Glaucoma is the leading cause of blindness in people over 60, and according to the American Academy of Ophthalmology, it affects an estimated 2.2 million people in the United States. That number is expected to increase to 3.3 million by 2020 as the U.S. population ages.
Marijuana for Glaucoma: An accidental discovery
Glaucoma is often the first condition people think of when referring to cannabis as a medicine. Ironically, medical marijuana’s glaucoma-fighting power was an accidental discovery during the War on Drugs. Intending to help law enforcement identify cannabis use through the classic side effect of “red eye,” UCLA researchers Drs. Robert Hepler and Thomas Ungerleider instead discovered the opposite: THC aids in relieving eye pressure.
In fact, Robert Randall, who is often called the “Father of Medical Marijuana” had glaucoma. Randall was one of the first patients to legally receive federally grown cannabis under the Compassionate Investigational New Drug (IND) program. He became the first legal marijuana smoker since marijuana prohibition was enacted in 1937. Despite doctors telling him he’d be blind by age 30, he maintained his eyesight through medical marijuana therapy until his death at age 53.
From the desk of our Pharmacists
THC has been shown to reduced eye pressure by 25 to 30 percent via activation of CB1 and GRP-18 receptors. Because its effects are short lived, dosing is generally suggested for every four hours. To treat glaucoma, eye pressure has to be maintained 24 hours a day.
CBD, on the other hand, in a recent animal study was shown to increase IOP by decreasing the affinity of THC at the receptor site (negative allosteric modulation). The same study showed that adding CBD to THC blocked the decrease in Intraocular pressure caused by THC. (1)
Both CBD and THC have neuroprotective effects, and these effects have been shown in some studies to protect the retina in models of glaucoma. (3)
Patients desiring to lower intraocular pressure with medical marijuana should stick to a THC-dominant preparation. Those with stable intraocular pressure who wish to protect the retina may benefit from a combination of THC and CBD.
Fun fact
In the 1970s, Dr. Hepler’s UCLA team also found that marijuana suppresses tear production. While contact lens wearers may grimace at this news, those who find themselves frequently crying while chopping onions may be delighted!
Of note
Neither the American Association of Ophthalmology, American Glaucoma Society, nor the Glaucoma Research Foundation endorses medical marijuana glaucoma treatment because of its controlled substance status, its short-acting durations, and because it can lower blood pressure resulting in less blood flow to the optic nerve.
This information is designed for educational purposes only. You should not rely on this information as a substitute for, nor does it replace, professional medical advice, diagnosis, or treatment. If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional. This information has not been evaluated by the FDA nor approved by any other government or official body. Nor is it intended to diagnose, cure or prevent any disease or disorder of any kind.
References:
1. Miller, Sally, et al. "Δ9-Tetrahydrocannabinol and Cannabidiol Differentially Regulate Intraocular Pressure." Investigative ophthalmology & visual science 59.15 (2018): 5904-5911.
2. Tomida, Ileana, et al. "Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study." Journal of glaucoma 15.5 (2006): 349-353.
3. [Rapino, Cinzia, et al. "Neuroprotection by (endo) cannabinoids in glaucoma and retinal neurodegenerative diseases." Current neuropharmacology 16.7 (2018): 959-970
4. https://www.ajo.com/article/0002-9394(72)90741-6/abstract