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What Current Research Tells us About Cannabis and Glaucoma

March 12, 2019   10:37 am PDT | Updated 2 years ago

Glaucoma is the leading cause of blindness for adults older than 60, afflicting nearly 61 million people globally. The condition is characterized by fluid buildup in the front part of the eye that leads to increased pressure within the eyeball. Over time, this pressure damages the optic nerve, causing a gradual and permanent loss of sight. There is no cure for glaucoma, but the disease may be treated with laser or traditional surgery, prescription eye drops, and oral medication.

There is evidence that the THC in cannabis can lower intraocular pressure (IOP) in a majority of individuals whether or not they have been diagnosed with glaucoma. As IOP is often a precursor to vision loss in glaucoma patients, could cannabis be an effective treatment option for the disease?

Research Overview

Since the 1970s, glaucoma has been one of the most frequently cited reasons to use medical marijuana. In fact, many sources attribute glaucoma to being the impetus for launching the medical marijuana movement.

The medical marijuana revolution began in 1974. Robert Randall, a 26-year-old man with advanced, poorly controlled glaucoma, observed that the halos around lights he experienced because of his high IOP disappeared after he smoked marijuana,” Dr. Thomas Graul, a board-certified ophthalmologist from Nebraska, wrote in an article published in 2018 in Glaucoma Today.  

Graul goes on in the article, however, to voice his skepticism about the efficacy of cannabis in treating glaucoma, but does the current research support his opinion?

The Studies

A 2015 study published in the Yale Journal of Biology and Medicine found, with cautious optimism, that cannabis could be beneficial to patients with end-stage glaucoma.

While standard options are superior to medical marijuana in the management of glaucoma, there may be a role of medical marijuana use in end-stage glaucoma patients who have failed maximal medical therapy and surgery or who are poor surgical candidates,” the authors of the study wrote.

A 2018 study conducted at Indiana University revealed contradictory results. Researchers found that the cannabidiol (CBD) in marijuana could actually worsen glaucoma by increasing eye pressure. In the study, CBD appeared to cancel out the beneficial effects of THC by increasing eye pressure in 18 percent of test mice. However, as this study was conducted on mice, it may be difficult to draw definitive conclusions without appropriate research on the effects of CBD in humans with glaucoma.

Photo by Amanda Dalbjörn

Could THC in isolation help patients with end-stage glaucoma? Most studies that connect THC to lowering IOP date back to the 1970s, and more contemporary research is vital to understand whether cannabis could help to manage glaucoma.

"There is literature — the literature isn't new — that shows marijuana can reduce the IOP, it just doesn't last long. You can't get away from the issue that marijuana can lower eye pressure, but the extent is still open for debate and the data is so old, who knows what we would find now,” said Dr. Murray Fingeret, a clinical professor at State University of New York College of Optometry.

Further, it has been shown that THC may only lower IOP for about three or four hours, while it would be necessary to keep the pressure at bay 24 hours a day for an optimal outcome. Despite these conflicting ideas about cannabis and glaucoma, some patients might be able to find relief for their eye disease.

Despite these conflicting ideas about cannabis and glaucoma, some patients might be able to find relief for their eye disease. Click To Tweet

Hypotheses are emerging on how glaucoma could be reclassified as a neurodegenerative disease, or a condition that affects the neurons in the brain. This classification is significant because cannabis has offered hope in treating other neurodegenerative diseases, such as chronic traumatic encephalopathy (CTE), a common brain injury in football players. But until more is understood about the biological basis of glaucoma, it is too early to say whether there could be a correlation between cannabis treatment for neurodegenerative diseases and for this particular eye disorder.

Patient Perspectives

Robert Randall, who died of AIDS in 2001, was one of the most outspoken activists for the medical marijuana movement, especially with regard to treating the glaucoma from which he suffered. A native of Sarasota, Florida, Randall moved to Washington, D.C., where he lobbied for the legalization of cannabis medicine and was nicknamed the father of the medical marijuana movement.  

In a 1998 book he co-authored, “Marijuana Rx: The Patients' Fight for Medicinal Pot,” Randall wrote: “In 1976 I became the first American to gain legal access to marijuana for medicinal purposes, specifically to treat glaucoma, a blinding eye disease. For the next twenty years, together with my partner and mate Alice O'Leary, I worked to expand this unique privilege to others.”

Throughout his life, Randall never stopped conveying his message of cannabis as a viable treatment option for glaucoma. Eighteen years after Randall's death, there are scant patient accounts of how cannabis may or may not benefit glaucoma. One 2016 study did, however, examine the attitudes towards medical marijuana of 204 patients with glaucoma. The results indicated that the majority of patients did not intend to use cannabis to manage their glaucoma.  

In regard to treating the symptoms of glaucoma, such as severe headaches, at least one public figure is advocating the use of cannabis in the form of vape pens. Actress Whoopi Goldberg, who has glaucoma, founded a medical marijuana company in 2016 targeting women patients. While the company, Whoopi & Maya, specializes in cannabis medicine for menstrual discomfort, Goldberg said she uses vape pens to ease her glaucoma-triggered headaches.

Of her vape pen, which she calls “Sippy,” Goldberg said, “It helps my head stop hurting, and with glaucoma your eyes ache, and she takes the ache out. It's wonderful.”

What the Experts Say

Some doctors are implementing cannabis into their medical practices to treat glaucoma. One such physician is Dr. Jason Zannis, founder of the primary care clinic Walk-In Wellness in Coral Springs, Florida. But Zannis does not represent the norm in his willingness to treat glaucoma patients with medical marijuana.

In his article, “Should You Be Smoking Marijuana to Treat Your Glaucoma?”, Dr. Henry D. Jampel, an ophthalmology professor at Johns Hopkins, argues against the use of cannabis as management for the eye disease.

“ ... [A]lthough marijuana can lower the eye pressure, recommending this drug in any form for the treatment of glaucoma at the present time does not make sense given its side effects and short duration of action, coupled with a lack of evidence that its use alters the course of glaucoma,” Jampel wrote.

Photo by George Evans

Jampel's opinion falls in line with that of the American Academy of Ophthalmology, the American Glaucoma Society, and the Canadian Ophthalmological Society, none of which presently view cannabis as a practical treatment option for glaucoma.

The Bottom Line

The current medical consensus suggests that cannabis is not a treatment for severe cases of glaucoma, though many states accept glaucoma as a condition qualifying for medical marijuana. In order for cannabis to be effective, high doses of THC would need to be administered into patients continuously, and marijuana's effects last only for a few hours at most. As a result, most prominent ophthalmologists maintain a skeptical or negative stance on the topic.