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Going Blind: The Debate on Cannabis Use for Glaucoma

The glaucoma cannabis debate
Written by Sarah Friedman

The debate over using cannabis to reduce high pressures related to glaucoma, continues; with still no long term studies available

Since the late 1900’s, a popular reason for medical marijuana use, is to treat glaucoma. Today, however, debate exists as to whether this is beneficial. Here’s the lowdown on cannabis for glaucoma.

What is glaucoma?

According to the American Academy of Ophthalmology, “Glaucoma is a disease that damages your eye’s optic nerve. It usually happens when fluid builds up in the front part of your eye. That extra fluid increases the pressure in your eye, damaging the optic nerve.”

It goes on to explain, “Your eye constantly makes aqueous humor. As new aqueous flows into your eye, the same amount should drain out. The fluid drains out through an area called the drainage angle. This process keeps pressure in the eye (called intraocular pressure or IOP) stable. But if the drainage angle is not working properly, fluid builds up. Pressure inside the eye rises, damaging the optic nerve.”

There are two types of glaucoma: open-angle, and narrow-angle. The more common version, open-angle, causes no vision changes at first. However, over time, an inability to properly drain this fluid in the eye, causes damage to accrue over time. Those who have this glaucoma, do not experience any pain.

Eye pressure test
Eye pressure test

The second version, narrow angle (or closed-angle), occurs in people whose iris is closer than it should be to the drainage angle. In this case, the iris can actually act as a block to proper drainage. If the iris blocks it completely (or mostly), pressure can build very fast, called an acute attack; and this can cause blindness very quickly. This kind of glaucoma often comes with eye pain, and feelings of sickness and headache. This kind of glaucoma can also build slowly, and often sufferers don’t know they have a problem, until the damage is done.

Glaucoma is a leading cause of blindness for those 60 and above, and the second most prevalent cause of blindness worldwide; with about 60 million approximated cases. According to glaucoma.org, more than three million Americans have it, but only about half know. Roughly 9-12% of these result in blindness, accounting for about 120,000 cases. This is a subject where African Americans sure don’t win out; as they are 6-8 times more likely than Caucasians to get glaucoma, and 15 times more likely to have vision impairment because of it.

Glaucoma damage cannot be reversed, and there is no medicine to cure it. Anyone can get it, including babies, but its more prevalent in older populations. It’s also very much genetic, and having family members who have it, means a greater probability of getting it. Diabetes, extreme nearsightedness, and being African American are other risk factors.

Cannabis and glaucoma

Long before cannabis re-entered the medical world as a possible treatment for a myriad of issues, it was still very much suppressed in terms of popular culture and medicine. However, in the early 1970’s, research started coming out indicating that cannabis could greatly help glaucoma sufferers from losing more vision.

The main reason for this connection, is that cannabis lowers intraocular pressures. Remember in the explanation of glaucoma, that the reason for damage is from rising intraocular pressures due to liquid not draining correctly, and building in the eye? Well, using cannabis keeps that from happening, or at least, decreases the amount of pressure. Now, before going on, to be clear, no one is contradicting this information. As in, it’s generally medically understood, that cannabis has this ability.

In 1978, the National Eye Institute began its own studies into the topic. This research produced results that indicated marijuana derivatives are able to briefly lower intraocular pressure; whether the plant is smoked, taken orally, or given intravenously. The organization did not find a benefit to topically applying it to the eye.

Can cannabis help with vision issues like glaucoma?
Can cannabis help with vision issues like glaucoma?

According to the article Marijuana and Glaucoma, published in Glaucoma Today, marijuana can lower intraocular pressure by 60-65%, but that this lasts for about 3-4 hours only. It also explains a dose-response relationship, whereby the amount consumed, is relational to the amount of pressure-reduction. However, greater amounts did not elongate the time frame of effectiveness.

One of the main reasons this caught on early, is because glaucoma medication have unwanted side-effects; then and now. These include (depending on medication): stinging, bleeding, burning, and itching of the eyes; fatigue; upset stomach; tingling hands and feet; memory problems; depression; lowered sex drive; shortness of breath; eye, and skin, color changes; drowsiness; frequent urination; droopy eyelids; and *lowered blood pressure – we’ll get to the importance of this one soon.

Why the debate over cannabis for glaucoma?

For as much as there is a known connection between cannabis and lowering eye pressures, its not an open and shut case. Perhaps this simply represents another example of official health platforms pushing people toward the pharmaceutical option; and maybe there is some value in the opposition. You can decide for yourself.

There are a couple issues with the use of cannabis for glaucoma. The first one is that it only works very temporarily. This could mean using it 6-10 times a day to keep pressure down. That’s a lot of getting stoned, and for people not interested in getting stoned, this is very problematic. It also means that if a person cannot take the weed frequently or regularly enough, then their pressures will go up and down; and there will be no consistency.

Along with this, there’s another issue. Glaucoma causes damage to the optic nerve from fluid building up. But other things, like low blood pressure, can also damage the nerve. Unfortunately, cannabis is often associated with lowering blood pressure. So it is possible that cannabis use can lower blood pressure enough to actually weaken the optic nerve more. However, remember that list of side effects? Pharmaceutical medications can lower blood pressure too, and they’re still used. Which makes it silly to point out cannabis for this.

What’s the uncomfortable problem here? There are no long-term studies. In fact, when you look up information on cannabis for glaucoma, while NO ONE argues that cannabis brings down pressures; somehow in all this time, no long-term or cohort studies were done. In fact, one paper which references progress into this topic, reported that as of 2006, despite constant complaints of having no long-term study, none were done. Now, nearly 20 years after that, and over 50 years after the first findings of cannabis lowering intraocular pressures, this still doesn’t exist.

Glaucoma is 2nd leading cause of worldwide blindness
Glaucoma is 2nd leading cause of worldwide blindness

Instead, you’ll find article after article positing ideas as to why it might or might not be okay for long-term use, but nothing more substantial. And that means that all these official health platforms are using the idea of blood pressure or being high, to rule it out; even though there’s no confirming information as to whether this possible dip in blood pressure, ever causes further issue.

So, let’s break it down. If a person doesn’t mind being high 24-hours a day, then using marijuana for glaucoma isn’t an issue in terms of getting high, so long as no tolerance to pressure-reducing effects is noted (and this can happen). Now, it could be an issue in terms of blood pressure reduction, but right now, that’s the part of this that’s unverified.

We simply don’t know if a reduction in blood pressure from cannabis can damage the optic nerve. In fact, one study referenced here, indicates that its higher blood pressure patients that see the biggest drop. Some of the studies in that review found a negligible effect on blood pressure altogether. If a specific patient doesn’t have a problem here, then it’s a moot point anyway; and if the FDA sees fit to use drugs like beta blockers (which also lower blood pressure) for treatment of the condition; then it seems this might not be the issue its made to sound like in the press.

For all the commentary out there, not one study exists that gives any insight as to whether the change in blood pressure from cannabis, can make glaucoma worse. And once again, this is now over 50 years after the introduction of cannabis to treat the condition; and an argument that takes place while pharmaceutical medications are prescribed, that are known to drop blood pressure.


If you’ve got glaucoma, you’re probably doing whatever you have to, to not go blind. For now, cannabis does provide a way to reduce pressures; however, there are certain factors which still after all this time, have not been appropriately examined at all.

As a side note, there is a new investigation into using DMT to treat glaucoma by way of a device that can apply the medicine directly to the eye. Those with the disorder should keep an eye on this story. All pun intended.

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About the author

Sarah Friedman

I look stuff up and and write stuff down, in order to make sense of the world around. And I travel a lot too.