Medical marijuana and the treatment of glaucoma

Cannabis has long been debated as a form of treating glaucoma and most medical marijuana programs warrant glaucoma as a qualifying condition.

Glaucoma is a complex disease that affects the eyes. affects over 60 million people across the world, and is the leading cause of blindness in adults over 60, according to the American Academy of Ophthalmology. With the recent progress in the legalization of medical marijuana, it has become easier than ever for patients to self-medicate using cannabis. But should they? What does the science say about using cannabis to treat glaucoma?


Glaucoma is a disease that damages the optic nerve inside the eye, which is responsible for transporting visual information back to the brain. To understand how this complex disease works, it’s best to have a simple understanding of how our eyes work first.

Light rays enter our eyes via the cornea before passing through the pupil and the lens of our eye. These rays are then focused onto the retina, a light sensitive tissue that lines the back of the eye. The retina is connected to the optic nerve, which is responsible for sending visual information and signals to the brain.

A clear liquid, known as aqueous humour, circulates the front portion of the eye. Aqueous humour serves to nourish the eye as well as maintain a constant healthy eye pressure. This fluid is drained through the trabecular meshwork.

The exact cause of glaucoma remains unknown. However, an increase in intraocular pressure is one of the main risk factors associated with the disease. This increased pressure is believed to cause damage to the optic nerve, which can result in a loss of a peripheral vision and eventually lead to blindness.

Intraocular pressure is caused by fluid build up within the eye, which may be caused by damage to the trabecular meshwork or ciliary body, which are responsible for draining and producing aqueous humour (respectively).

Other factors like ethnicity, family history, high blood pressure, and obesity are also believed to influence one’s risk of glaucoma.


There are two main types of glaucoma. Primary open-angle glaucoma is the most common, and is known to have a gradual onset, as the eye becomes progressively worse at draining fluid. As this happens, fluid begins to build up in the eye, causing a patient’s intraocular pressure to rise and damage the optic nerve. Primary open-angle glaucoma produces no obvious signs or vision loss at first.

Closed-angle glaucoma, on the other hand, affects people whose iris is abnormally close to the trabecular meshwork, ultimately blocking the eye’s drainage system. When this happens, eye pressure rises very quickly which can lead to blindness. This is known as an acute attack, and is characterized by the following symptoms:

  • Sudden blurry vision.
  • Sever pain in the eyes.
  • Nausea and vomiting.
  • Seeing rainbow-colored rings or halos around lights.

Closed-angle glaucoma usually develops slowly and is often a chronic condition. Like open-angle glaucoma, it doesn’t produce any symptoms at first until an acute attack takes place. Patients who suffer from an acute attack are advised to contact their ophthalmologist immediately.


Glaucoma treatment is generally concerned with lowering the intraocular pressure within the eye. Ophthalmologists tend to do so using 3 main types of treatments:

  • Eye drops.
  • Traditional surgery.
  • Laser surgery.


The idea that cannabis may help to lower intraocular pressure (IOP) and thereby help treat or prevent glaucoma originated in the 1970s. Medical studies at the time (like the 1971 study titled Marihuana Smoking and Intraocular Pressure by Hepler and Frank) showed that smoking cannabis helped glaucoma patients effectively lower their IOP and warranted further research.

In the following years, investigators expanded on this research and began taking a closer at cannabis and its potential as a treatment for glaucoma. Some studies looked at the effectiveness of smoked cannabis while others also tested other routes of administration, including ingestion and IV (intravenous administration).

It’s important to understand that the research done at this time didn’t just look at whether smoking a joint could lower a patient’s IOP. Instead, researchers looked at a variety of cannabinoids found in cannabis plant material and tested them both individually and in combination with one another. One study, published in 1984, for example, tested a number of cannabinoids (including multiple derivatives of THC and others) for their effect on the IOP of a rabbit.

Cannabis contains over 100 of these cannabinoids and a complex mix of terpenes, which are the key players in the plant’s role as a medicine. Unfortunately, most of the research to date is only concerned with a handful of these cannabinoids, most notably THC and CBD.

When cannabis enters our body, these molecules interact with our body’s endocannabinoid system, which is a system that occurs naturally in humans and other mammals and produces its own cannabinoids. This system is made up of a group of cannabis receptors (known as CB1 and CB2), which are found in various parts of the brain and body, including the central nervous system. Most importantly for the medical marijuana-glaucoma discussion is the fact that these receptors have been found directly located in the tissue of the eyes.

Today, there is a strong consensus around the medical community that the cannabinoids found in marijuana can lower intraocular pressure significantly, sometimes up to 25-35%, making it as effective as other regular glaucoma medication. However, medical marijuana has one major setback when it comes to treating glaucoma; cannabis is only able to reduce intraocular pressure for about 3-4 hours.

In order to be effective, a patient’s IOP needs to be managed 24 hours a day, meaning they’d have to medicate with cannabis around 4-6 times daily. This is a major setback, seeing that cannabis is intoxicating and can leave people unfit to drive, handle machinery, and complete a variety of other tasks.

Besides that, smoking cannabis in a traditional way is not really good for the lungs. While non-smoking methods like ingestion (via an edible, pill, or capsule) or vaporizing obviously avoid the harmful effects of smoking, they still don’t offer a long-term solution.

To deal with this, researchers began looking at topical solutions like cannabinoid-rich eye drops, as they target the eye directly, avoid the health risks of smoking, and possibly offer long-term effects. Unfortunately, due to the fact that THC and other cannabinoids are not very soluble in water, the eye drops didn’t prove very effective, with only around 5% of an administered dose effectively hitting the target.

Today, most ophthalmologists don’t see cannabis as a viable treatment for glaucoma. This is mainly due to its side effects, short duration, and difficulty in administering it in a way that maximizes the benefit:risk ratio.


Although the research into cannabis and glaucoma suggests that, at least for now, cannabis doesn’t offer a viable alternative for regular glaucoma treatment, glaucoma is momentarily listed as a qualifying condition under many state medical marijuana programs in the US, including those of Alaska, Pennsylvania, Oregon, Nevada, and more.

This has made it easier than ever before for glaucoma patients to self medicate with cannabis. And, despite the clinical research, many claim it's a viable solution that far outshines traditional treatment.

A handful of medical professionals, dispensaries, and even big pharmaceutical companies like GW, do stand behind cannabis as a glaucoma treatment. This discrepancy makes it hard to come to a solid conclusion on which side of the fence to sit on when it comes to the marijuana-glaucoma debate. However, we like to remain hopeful that, with constant innovation in the cannabis industry, we’ll soon find a suitable way to treat glaucoma using medical-grade marijuana.

To find out more about cannabis as a treatment for glaucoma, contact your ophthalmologist or healthcare professional.

Note: We have taken the utmost care and precaution whilst writing this article. That being said, please take note of the fact that we are not medical professionals of any kind. is strictly a news and information website. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment.