Cannabis and Glaucoma: What Does the Research Say?

The ability of cannabis to improve the symptoms of glaucoma has been demonstrated in various studies, but doubts still remain over its efficacy and consistency within patient populations. Despite this, it is one of the most common reasons to request medicinal cannabis. We review the research and the limitations of cannabis as a medicine for glaucoma.

Glaucoma is the second leading cause of irreversible blindness worldwide. It has been known since the 1970s that cannabis can be an effective treatment, but concerns about side effects have made the medical community reluctant to endorse it. On top of this, the dosage required for a notable therapeutic effect may make cannabis treatment unaffordable and inefficient. Let’s explore cannabis as a treatment for glaucoma and compare it with conventional pharmaceutical treatment.

What is glaucoma?

Glaucoma affects over 70 million people worldwide, of which 10 % are completely blind. This insidious condition can remain symptomless until it is well advanced, making it likely that the 70 million sufferers represent the tip of an iceberg of undiagnosed glaucoma. The condition is most prevalent in older people, in those with a family history of glaucoma, and in people of African ancestry.

Glaucoma is usually associated with high pressure in the eye, or intra-ocular pressure (IOP). This pressure can cause stress and strain on the components of the eye, leading to the death of retinal ganglion cells, which are responsible for transmitting information from the retina to the brain. Patients experience irreversible vision loss once this link between the eye and the brain is severed.

Two kinds of glaucoma: open-angle and angle-closure

There are two categories of glaucoma, open-angle glaucoma and angle-closure glaucoma. Open-angle glaucoma accounts for at least 90% of all glaucoma cases, but angle-closure glaucoma is more severe, and more likely to lead to complete vision loss.

Both open-angle and angle-closure glaucoma are associated with high pressure in the front part of the eye which contains the cornea, iris and lens. It is normal for the eye to be under pressure – this is how the eye maintains its roughly spherical shape and keeps its walls taut.

The pressure is caused by a fluid in the eye called the aqueous humour, which is like blood plasma but with less protein in it. In a healthy eye, this fluid flows from the edges of the eye into the space between the iris and the lens. The fluid passes out through the pupil into a space between the iris and the cornea, before draining out at the edge of the eye through structures known as the trabecular network.

In open-angle glaucoma, the iris is correctly located, but the trabecular network does not drain properly. In closed-angle glaucoma, the iris is pressed up against the cornea, and this blocks the trabecular network from draining. These are the two ways that intraocular pressure increases as a result of glaucoma.

Much remains to be discovered about glaucoma. It is clear is that intraocular pressure is related to retinal ganglion cell death. However, the biological basis of glaucoma and the factors contributing to its progression are poorly understood. Many people remain asymptomatic until late in the disease progression, while others have intraocular pressure in the normal range but still develop glaucomatous optic neuropathy.

Effect of cannabis on glaucoma

The efficacy of cannabis in lowering intra-ocular pressure is well known, having been first reported in 1971. Pharmacologist, Prof. Manley West and his ophthalmologist colleague, Dr Albert Lockhart, reported the use of cannabis in the treatment of glaucoma in 1978.

West went on to develop cannabis-based eye-drops for the treatment of glaucoma and in 1987 gained approval to market them in Jamaica under the name “Canasol”. Canasol contains no psychoactive cannabinoids. Though approved for use in Jamaica only, it has reportedly also been prescribed in a number of countries around the world.

West has further developed Canasol into Cantimol, a combination of Canasol and the beta-blocker Timolol Maleate. Animal and clinical trials of Cantimol have been carried out in Jamaica, and the drug will be available in Jamaican pharmacies once it has cleared the local approval and registration process. Like Canasol, Cantimol is likely to remain a Caribbean secret, for there are no plans to submit the drug for the prohibitively expensive FDA approval process required to market it in the USA.

Why have the medical community been reluctant to accept cannabis as a treatment for glaucoma?

The medical understanding of cannabis and its effects on intraocular pressure have not changed since the 1970s. It is typically accepted by the medical community that cannabis reduces intraocular pressure. However, much of West’s research went unnoticed, probably because it was published in obscure journals without much exposure.

Glaucoma is one of the most commonly cited reasons for using cannabis medicinally, and it was the first indication for which the US federal government approved medicinal cannabis. However, as research continues into the topic, the medical community is reluctant to call cannabis an effective medicine for glaucoma. This is because, like many other glaucoma medications, the risks seem to outweigh the benefits. Cannabis’ effects on intraocular pressure are short-lived, for example, requiring heavy and frequent dosing.

To reduce intraocular pressure to the normal range and maintain that range, patients would have to ingest 18-20 mg of THC six-eight times a day, every day. This is an exceptionally high dose of THC to ingest, let alone up to eight times a day. This would dramatically interfere with a person’s ability to carry out normal activities such as driving and working. On top of this, there may be side effects relating to sleep, mood, and psychology.

Tolerance has been another reluctance of the medical community, although this is less justified. A study compared the ophthalmological characteristics of Costa Ricans who had used cannabis for ten years or more with those of non-using controls. If significant tolerance to the intra-ocular pressure lowering properties of cannabis had developed in the cannabis users, the two groups would be expected to have the same IOP. 

Despite enforcing a 3-10 hour abstinence prior to ophthalmological testing, cannabis users exhibited lower intraocular pressure than non-users. This suggests that the intraocular pressure lowing properties of cannabis were still apparent after ten years of daily use.

For glaucoma treatment, the difference between THC and CBD is enormous

CBD has become increasingly popular in the last 5 years, and many of those seeking the therapeutic benefits of cannabis have turned to CBD. Unfortunately, this isn’t a viable option for those with glaucoma.

The intraocular pressure reducing properties of cannabis can be attributed almost entirely to THC. In one study, CBD did not reduce intraocular pressure, but at a dose of 40 mg, actually produced a transient increase in intraocular pressure. In another study, researchers found that CBD actually prevented THC from fully exerting its reducing effects on intraocular pressure.

Thus, it seems that it is virtually impossible to mitigate the negative side effects of THC by using CBD instead. In fact, even a full-spectrum cannabis extract may not suffice in the treatment of glaucoma, given the study findings that CBD reduces THC ability to reduce intraocular pressure.

A comparison with pharmaceutical treatments

At present, lowering intraocular pressure is the only proven therapy for glaucoma. There have been several experimental treatments such as treatment with neuroprotective agent, memantine. However, this treatment was unsuccessful at slowing the progression of glaucoma.

Conventional treatments focus exclusively on lowering intra-ocular pressure, despite the fact that not all sufferers have high intra-ocular pressure and some people with high intra-ocular pressure remain asymptomatic. The treatment regime varies depending on the type of glaucoma.

For open-angle glaucoma, Prostaglandin analogues are the primary line of treatment. For those who don’t respond to this treatment, a range of options exist: β-Adrenergic blockers, α-Adrenergic agonists, carbonic anhydrase inhibitors and cholinergic agonists, though all are less effective than prostaglandin analogues.

In the event that a patient doesn’t respond to any treatment, there is an option for surgery. For open-angle glaucoma, laser trabeculoplasty is performed. It is effective at reducing intraocular pressure, although the effects don’t last forever.

For angle-closure glaucoma, the first line of treatment is to make a hole in the iris using laser peripheral iridotomy. If this doesn’t reduce pressure, drug treatments similar to those used in open-angle glaucoma can be used.

Acute angle-closure glaucoma is treated as a medical emergency due to the risk of vision loss. First, medications are used to affect an immediate reduction in pressure. An iridotomy is then performed.

Something that greatly separates pharmaceutical intervention from cannabis treatment is cost. Research has suggested that a patient would need to smoke 1.5 g of cannabis per day to maintain low intraocular pressure, at a total cost of $8,820 per year. This compares to an annual cost of anywhere between $150 and $873 for topical glaucoma medication in the USA.

On the contrary, Cantimol produced in Jamaica is expected to retail for about $250 per vial. This makes the annual cost of Cantimol very competitive with pharmaceutical options.

Future directions

Recent years have seen the demonstration of endocannabinoid intraocular pressure mechanisms and the discovery of CB1 receptors within the eye. This suggests that cannabinoids are involved in the regulation of normal ocular tension, and has led to widespread interest in the development of cannabinoid-based glaucoma drugs. 

Topical delivery of such drugs directly to the site of action should eliminate psychoactivity. Armed with such new medicines, the management of glaucoma will be able to move beyond the simple intra-ocular pressure reduction offered by conventional therapies, unlocking the following additional mechanisms through which the development of glaucoma may be managed:

  • Neuroprotection
  • Vasodilation
  • Antioxidation
  • Anti-inflammation

Such new therapies will be particularly welcomed by individuals who develop glaucomatous optic neuropathy despite having intraocular pressures within the normal range. Provided such new therapies are supported by high quality clinical trials, there may be an entirely new angle through which to tackle the problem of glaucoma.

  • Disclaimer:
    This article is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with your doctor or other licensed medical professional. Do not delay seeking medical advice or disregard medical advice due to something you have read on this website.

Comments

30 thoughts on “Cannabis and Glaucoma: What Does the Research Say?”

  1. Rozar@Abud-e.com

    Medicinal Marijuana and also Marijuana products have been proven to lower the IOP level within individuals that is a major cause of Glaucoma. Medicinal Marijuana has THC that is the useful component that keeps IOP level very low.

    1. Kelly Barton

      I just had a Ahmed valve placement in my eye for glaucoma pressure being 50 and no longer controlled with drops. My question is my other eye is showing signs of pressure increasing even on many drops daily. That surgery was rough.. not really wanting another. Would medical cannibis be warranted. Thanks for any advice.

      1. Charles Tate

        Hi, Kelly — I am a glaucoma patient, and have used medical marijuana, in addition to the pharmaceutical eyedrops. I have not had any surgery.

        When I first decided to try medical marijuana (MMJ) for my glaucoma several years ago, I asked my ophthalmologist and he said, “I am in favor of anything that brings your pressure down. If you want to try it, go ahead.” He had never written a (California) 215 recommendation letter before, but he wrote mine. When I next came into his office after “using medical marijuana” (in this case, smoking some weed), he tested my eye pressure and started practically jumping up and down. “Oh. This is fantastic! This is fantastic!”

        Within a year, he had quit most of his regular ophthalmology practice, and was now almost exclusively a marijuana doctor — he found he could help people more that way, and get people off of Vicodin and other addictive or harmful drugs, due to the medicinal properties of marijuana.

        Back to me and my eyes. I have a non-contact tonometer (NCT) at home. This lets me test my pressure as many times as I want to during the day. However, since I have not stopped using the drops (too concerned that might be a horrible mistake), it is hard to get a handle on just how effective marijuana is at lowering IOP (intra-ocular pressure). But since MMJ has other beneficial effects insofar as glaucoma, I generally feel it is a good idea.

        In my case, recently I felt I needed to stop smoking weed, so I could get more work done! But I love it, am sure it helps my eyes, and will probably go back to it eventually. Meanwhile, the drops (Travatan Z and Simbrinza) are keeping my pressure mostly under 20.

        What I really want to find is MMJ eyedrops for glaucoma. Some Jamaican doctors developed a non-psychoactive cannabis-extract eyedrop. I tried it, and it had some IOP-lowering effect, but I did not really test it very much because I found out it had Thimerasol, a mercury preservative, in it. (Skeptics please see the article, Mercury is Not Safe in Any Form: Debunking the Myths About Thimerosal “Safety”, by Robert F. Kennedy, Jr.) That tore it for me and I stopped using the drops and started smoking.

        But that was like 10 years ago, and this is 2018, and marijuana is legal in more and more places. Isn’t someone making a nice, high-quality THC (and/or other cannabis components determined to help glaucoma) eyedrop yet?

        Love,
        Chas

  2. Please recommend a clone strain of cannabis that I can grow at home. My mom has severe glaucoma, is on 2 drops, and has had laser surgery to open the ducts in her eyes. She will kill herself if she goes blind, so I really want to prevent that!!!! We are both willing to do anything that helps.

  3. Your website was in the listing I pulled up when I googled cannabis and glaucoma. I selected your listing because it said ” the ability of cannabis to improve the symptoms of glaucoma has been demonstrated in various studies. You have a very well written article that has NO REFERENCES TO STUDIES. Disappointing.

    1. Linda Matthews

      You should be able to find references yourself. Just Google “medical abstracts/studies showing the efficacy of marijuana on glaucoma”. If it doesn’t show up you can look for the studies under the doctor’s name/country. Many abstracts can be found in full for free, but if not there should at least be a synopsis that likely will answer your questions. Frankly this is a good thing to know just in general regarding new tests, studies and possible treatments, effects of probotics on many diseases, supplements and even foods eaten. Also I’ve found way more stuff, especially obscure items on Google.

  4. Marc Lieberman, M.D.

    This account is not well rooted in the medical literature, and exaggerates the effectiveness of cannabis. The brief lowering of the internal eye pressure ( IOP= intraocular pressure) is NEITHER as persistent NOR as effective as obtained by readily available, generic topical eye drops for glaucoma. Moreover, the cannabis effect on the complex blood pressure gradients within and behind the eye itself— felt to play a role in glaucomatous damage— have not been teased out, and hence its many active agents may be working counter to its effects of transient pressure-lowering….

    A definitive & up-to-date summary article was recently published by Gary Novack, PhD., a renowned ocular pharmacologist: Curr Opin Ophthalmol 2016, 27:146 – 150. As with many other promising medical effects of cannabis on human biologic systems— such as relieving pain, spasticity, etc.— more effective ‘mainstream’ treatments are better documented and effective. Perhaps the modest-at-best role of cannabis products might be as an adjunct— but NOT a substitute— for pharmacologically & effective professional management of this potentially blinding eye disease.

    1. Scarlet Palmer - Sensi Seeds

      Dear Marc,

      Thank you for your comment and feedback on this article. I will bring it to the author’s attention so that necessary amendments can be made.

      With best wishes,

      Scarlet

    2. Mr Lieberman,

      I have been suffering from uveitis these past 3 years and doctors say they can’ do nothing but prescribe me cortisone, i still have inflammation in my optic nerve.
      I would like to ask you if you think that cannabis could help me get rid of this disease? or at least make the inflammation disappear, my ophtalmologist says that if it continues this way I might loose my sight.

      Thank you a lot,

      Maria L

  5. Need info for canbabis oil for acute open angle glaucoma with macular degeneration please !!!

    1. Scarlet Palmer - Sensi Seeds

      Dear Tdog,

      Thank you for your comment. We are sorry to hear about your situation. Unfortunately, as Sensi Seeds is not a medical practice, we are not able to provide any advice relating to medical situations other than to consult your doctor or other licensed medical professional. This article, written specifically for healthcare providers who may not be aware of the many properties of cannabis, may be useful to you in talking with your doctor. You could also try to contact local medicinal cannabis support groups, if you have not already done so. In the UK, there is the United Patients Alliance (you can find them on Facebook) and in the US and EU there are many branches of NORML (google NORML followed by your area name). We hope this is helpful.

      With best wishes,

      Scarlet

  6. Al Morentin

    I have the painful kind of Glaucoma. It’s aggressive and it hurts really bad… as well as vision loss in my right eye… It took a long while to find a solution for myself… I have been managing my Glaucoma with cannabis oil, a healthy diet, and proper supplementation for the past 3 years. It took me a long while to figure it out, but I’ve stopped mine in its tracks and actually improved my vision… It’s a little bit of work, but my eyesight is worth it… And, the other really awesome thing is the fact that I have the pain under control for the most part… I still get flare-ups from time to time, but 3 years ago I was in pain every waking moment of the day… every day… I basically have my life back.

    Just wanted to share a glaucoma success story because I know there aren’t a lot of them out there.

    1. Scarlet Palmer - Sensi Seeds

      Hello Al,

      Thank you for sharing your story, it is indeed really good to hear success stories and I’m really glad you have been able to improve your quality of life.

      With best wishes,

      Scarlet

      1. Wow, thats encouraging because doctors make you fell there is no hope. Now, i have to find the oil drops

    2. Lesley Corriveau

      I have just started cannabis oil for my glaucoma. Do you put the oil under your tongue or is it like an eye drop. I am new to this and I am taking the oil about half the size of a grain of rice and rubbing it on my gums. What is the name of the oil you are using. I would appreciate you getting back to me.

    3. What type cannabis oil did you use
      . My grandfather has it and he been look all over for a good cannabis oil to help Him out

    4. Organiclife

      I have been producing Cannabis and using it to treat a lot of ailments including cancer, epilepsy, diabetes and glaucoma. No one can tell me otherwise, it works really well for glaucoma.
      Combined with a proper organic plant based diet , nothing beats it.

      1. Hi Organic life?
        I can’t get a clear answer anywhere about the oil. Can I ask if it’s the RSO with the high THC content or the CBD oil that actually helps with the Glaucoma. Thank you in advance. Cynthia

    5. Al Morentin

      Oh my goodness thank you so much for your success story, I am so happy for you to have found something to relieve your pain. My glaucoma was diagnosed quite late when I had just turned 42 in Nov 2016. I was supposed to see my optometrist in hospital every 3 months but I have only seen her twice to date. My right eye is most affected where I can feel it but not see through it clearly. Please may I ask where you source the cannabis oil and at what grade, also which supplements do you take? Any advice I would be extremely grateful for. If you would prefer to email me please let me know and I will happily forward it to you. Much love. Dona

  7. George Cohen

    I, too, have glaucoma & I’m looking for CBD oil, or cannabis oil that might help–
    1–where can I buy some?
    2–how much do I use?
    3–Is it under the tongue–sublingual, or applied onto the eyes?
    4 my brother has uveitis–same questions for his condition.
    THANK YOU.

    1. Scarlet Palmer - Sensi Seeds

      Hi George,

      Here you can read more information about Sensi Seeds CBD Oil, including how to take it. Unfortunately, as Sensi Seeds is not a medical practice, we are not able to provide any advice relating to medical situations other than to consult your doctor or other licensed medical professional. This article, written specifically for healthcare providers who may not be aware of the many properties of cannabis, may be useful to you in talking with your doctor. You could also try to contact local medicinal cannabis support groups, if you have not already done so. In the UK, there is the United Patients Alliance (you can find them on Facebook) and in the US and EU there are many branches of NORML (google NORML followed by your area name). We hope this is helpful.

      With best wishes,

      Scarlet

  8. For anyone who’s interested my bass line intraocular pressure is at 30 so quite high but after a smoke its at 26 still to high but better than 30. Back in the day I Bass lined at 24 and after a smoke my IOP was 20 so for my eyes a smoke reduces my IOP by 4.

  9. I have started taking CBD oil for other conditions, but have a question regarding it and eye pressure. The CBD oil I am taking does not contain THC. Will it still lower IOP? I ask because I have the opposite problem to glaucoma, low eye pressure (hypotony). I have had a surgery for glaucoma (trabulectomy) and then a second surgery seven years ago to correct low eye pressure that developed. After starting CBD, it appears low eye pressure has developed again. Very concerning. Have stopped for now, but am curious if it could be playing into this. It would seem like it would, if cannabinoids can lower IOP 25-30%. Any information on this would be most helpful. I’m disappointed I can’t continue the CBD, if this is the case, as I was enjoying taking it, it really has helped my mood.

    1. Scarlet Palmer - Sensi Seeds

      Hello Joy,

      Thank you for your comment. We are sorry to hear about your situation. Unfortunately, as Sensi Seeds is not a medical practice, we are not able to provide any advice relating to medical situations other than to consult your doctor or other licensed medical professional. This article, written specifically for healthcare providers who may not be aware of the many properties of cannabis, may be useful to you in talking with your doctor. You could also try to contact local medicinal cannabis support groups, if you have not already done so. In the UK, there is the United Patients Alliance (you can find them on Facebook) and in the US and EU there are many branches of NORML (google NORML followed by your area name). We hope this is helpful.

      With best wishes,

      Scarlet

    2. JOY I would very much like to learn more about your situation- do you have LOW tension glaucoma? Or low blood pressure?
      Dont know if I can post my email but I am going to and if you see it can you email me? Thanks

  10. Medicinal Marijuana and also Marijuana products have been proven to lower the IOP level within individuals that is a major cause of Glaucoma. Medicinal Marijuana has THC that is the useful component that keeps IOP level very low.

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