As Toronto optometrists, we feel it’s our duty to report on cannabis’ effectively as a glaucoma treatment.

With medical marijuana already legal in Canada and with recreational legalization imminently on the horizon, some Canadians are questioning whether cannabis, with its long association as a treatment for various medical conditions, can help their glaucoma, too.

It’s a valid question; after all, the medicinal properties of cannabinoids have made them the treatment of choice for some patients suffering from everything from chronic pain to cancer to neurological diseases, so why not ocular diseases, too?

The key is to take a look at what the evidence shows.

Despite Science, Folklore About Marijuana and Glaucoma Persists

There are, of course, different types of evidence – and anecdotal evidence can be powerful.

When many people state that they or someone they know believes something to be true, it can take on a life of its own and convince others without any hard evidence whatsoever.

Unfortunately, that sort of thinking can lead to serious public health issues, such as parents rejecting vaccinations for their children. Even medical facts for which corroborated studies exist, are a moving target because new and contradictory evidence is constantly being released.

For example, entire generations decided that trans fats were good for you (we now know them to be bad) – and many people still avoid eggs to this day because of their cholesterol, even though studies show that human cholesterol isn’t derived from diet!

Something similar seems to have happened with cannabis.

Back in the 70s, when marijuana was a popular (if still illegal) recreational drug, studies reported lower IOP (intraocular pressure) when marijuana was administered. But even those studies found that the effect was insufficient to manage glaucoma long term.

In fact, marijuana can actually harm people with glaucoma because it lowers blood pressure, which in turn lowers the flow of oxygenated blood to the optic nerve.

As well, because most patients with glaucoma are over 60 years of age, doctors are concerned with their using marijuana because of potential side effects that are more pronounced and/or more dangerous in this age group, such as:

• Falling due to dizziness or that ‘high’ feeling
• Poor motor coordination
• Suppressed immune system
• Elevated heart rate
• Problems with cognition, memory and concentration
• Lung and breathing problems if the cannabis is smoked
• Eye problems such as age-related macular degeneration and cataracts, for which smoking is a leading factor

Another problem with the results of the research about using marijuana to lower intraocular pressure is that the IOP-lowering effects of cannabis only last a few hours. Patients would literally have to consume marijuana every few hours, around the clock, to maintain the desired result. We’ll stay away from that one!

How to Treat Glaucoma More Effectively than with Marijuana

If you are considering marijuana as an alternative to conventional medicine, it’s your decision – but be sure you know the facts, as well.

Glaucoma is a progressive disease that worsens without treatment, and that vision loss is irreversible.

Prescription medication, usually in the form of prescription eye drops that must be administered once or twice daily, is an effective way of lowering intra-ocular pressure 24 hours a day; microsurgery and laser eye surgery treatments are also available and are scientifically proven, in repeated trials, to delay glaucoma progression.

The best way to prevent glaucoma is to get a regular eye exam, but if you already have the disease, and are struggling with your current medication or course of treatment, ask your trusted optometrist first before embarking on a new treatment regimen.