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Medical Cannabis for Glaucoma: Does Cannabis Improve or Worsen Glaucoma Symptoms?

17 January 2023

An older man scratching his eyes while struggling to look at phone display

Key Points

  • A leading cause of blindness worldwide, glaucoma is a disease of the optic nerve that produces progressive vision loss over time. It’s primarily caused by increased intraocular pressure (IOP) but may also result from inflammation or oxidative stress.
  • One of the leading treatment options for glaucoma is medications that reduce IOP. Medical cannabis has been shown to help lower IOP levels, thus making it a prime candidate for glaucoma treatment.
  • Though THC can help reduce intraocular pressure, the dose required to see any desired effect is extremely high and may result in unwanted side effects. THC may worsen glaucoma conditions by lowering blood pressure in the optic nerve.
  • Cannabidiol (CBD) may help address glaucoma by reducing oxidative stress, relieving inflammation, and activating pathways in the optic nerve. However, research remains conflicting on the effectiveness of CBD for glaucoma treatment.
  • Those seeking to use medical cannabis oil for glaucoma treatment should discuss the risks and benefits with a doctor. Cannabis medication may interact with other medications the patient may be taking, so an expert opinion is highly recommended.
  • Experts at Lyphe can evaluate your condition, determine whether medical cannabis is a good option for you, and prescribe the medication to you. 

Glaucoma is a group of eye diseases that cause nerve damage and loss of vision. Glaucoma has no definitive symptoms, and most people only discover they have it during a routine eye exam. The condition is best characterised by an increase in intraocular pressure (IOP), which causes damage to the optic nerve.

Nearly 2% of the UK population over 40 suffers from this progressive condition. Glaucoma is the second leading cause of blindness, only behind the more prevalent cataract. Left untreated can lead to total blindness in the affected eyes.

Conventionally, glaucoma is treated with medication that lowers IOP. Medical cannabis gained popularity as a potential treatment thanks to a study published in the 1970s. In the study, researchers found cannabis helped lower IOP, like other medications did.

Given the need for alternative treatments, more people are turning to medical cannabis for glaucoma. Is it all just hype and medical myth? Or can medical cannabis actually help lower IOP and treat glaucoma? Let’s take a closer look at the evidence.

Glaucoma: symptoms, causes, and diagnosis

Glaucoma stock illustration
Glaucoma. Detailed anatomy of Glaucoma and healthy eye.

Glaucoma is a condition that affects the optic nerve. The optic nerve transports information from your eyes to your brain. When it becomes damaged, you may lose peripheral vision and experience blurry vision and pain in your eyes.

Glaucoma usually starts between ages 40 and 60; however, it can affect people at any age. It is the second leading cause of blindness in the world. People with glaucoma often experience no symptoms until the condition has progressed to a later stage.

The symptoms of the eye condition depend on its type:

  • Open-angle – This is the most common type of glaucoma. It causes peripheral vision loss and blurry vision. The condition may develop slowly over time, and people with open-angle glaucoma often don’t notice any symptoms until they have lost a significant amount of peripheral vision.
  • Closed-angle/Acute – This type of glaucoma is less common but more serious than open-angle glaucoma. It causes severe eye pain and halos around lights. This condition can cause blindness within hours if left untreated. Patients who suffer from an acute attack (also known as an episode) can experience sudden severe pain.
  • Normal tension – This glaucoma is rare and often causes no symptoms. It’s sometimes called low-tension glaucoma and may be difficult to detect because it doesn’t cause pain or vision loss in its early phases.
  • Pigmentary – This condition occurs in people with darker skin tones and causes the eyes to appear red. It’s a type of glaucoma that causes gradual side vision loss.

The typical progression of open-angle glaucoma is slow, so it’s possible to have few complaints until the disease has advanced. In other words, most people with this type of glaucoma don’t realise they have it until their vision is significantly impaired.

Causes

Open-angle glaucoma usually occurs as a result of damage to the optic nerve. The optic nerve is the structure that carries information from the retina to the brain. If this area is damaged, it can lead to vision loss and even blindness.

One of the most common causes of optic nerve damage is increased intraocular eye pressure (IOP). Eye pressure measures how much the eye can focus on objects and images. Normal eye pressure ranges between 12 and 20 mmHg, but many factors can cause it to vary:

  • Ageing
  • Other types of eye disease, such as macular degeneration and diabetic retinopathy
  • Brain problems (e.g., stroke)
  • Inflammation and oxidative stress (caused by free radicals)
  • Trauma to the eye and brain (e.g., head injury
  • Presence or spillover of glutamate in the eye

Diagnosis

A healthcare provider can diagnose glaucoma through a comprehensive medical examination that includes the following:

  • A visual acuity test measures how well a person can see at various distances.
  • A tonometry test to check the pressure inside the eye. The healthcare provider will place a thin tube in your eye and inject a liquid that causes mild discomfort. The pressure is then measured by how much this fluid comes out of the tube into a container.
  • Eye dilation examinations and imaging tests to rule out optic nerve damage and to determine the extent of damage to the optic nerve
  • A visual field test measures how much peripheral vision you have and whether or not you can detect movement.
  • Pachymetry is a test that measures the thickness of your cornea. Your cornea is the clear, dome-shaped tissue on the front of your eye.

The age at which the patient is diagnosed with glaucoma will depend on how quickly the condition progresses. As such, it is of utmost importance for patients to have their eyes diagnosed with glaucoma if symptoms are present. In cases of acute glaucoma, immediate treatment is necessary. Always consult with your doctor. 

Current treatment options for glaucoma

Elderly woman eyesight test with binocular slit-lamp
Elderly woman eyesight test with binocular slit-lamp. Checking retina of a female eye close-up. Ophthalmology Clinic

Glaucoma treatment options include medication, laser treatment and surgery.

Medication

Medication for glaucoma includes beta-blockers to control intraocular pressure (IOP) and medications that target ocular inflammation, such as prostaglandin analogues. Most of these medications come in an eye drop form. However, some cases require a prescribed oral medicine to bring IOP further down. Always consult with you doctor. 

Possible side effects of glaucoma medication include:

  • headaches, nausea, and dizziness
  • frequent urination
  • increase in heart rate and blood pressure
  • eye discomfort and redness
  • blurred or dimmed vision

Surgical treatment

In more serious cases, glaucoma can only be treated with invasive methods:

  • Laser trabeculoplasty (LTP) is a procedure that uses a laser beam to treat open-angle glaucoma by creating a hole in the trabecular meshwork of the eye to allow fluid drainage. LTP can be used alone or with other surgical procedures like cataract extraction or trabeculectomy.
  • Trabeculectomy is the surgical removal of a portion of the white of the patient’s eye. This creates space for fluid to drain out of the eye.
  • Drainage can be accomplished by creating a tube that drains fluid or implanting a shunt.

Medical cannabis for glaucoma: the science and pharmacology behind it

In 1970, a group of researchers published a study on the effects of cannabis on glaucoma patients. The conclusion was that smoking cannabis could reduce intraocular pressure by 25 per cent. Ever since this finding was presented, there’s been a debate about whether or not cannabis is a viable treatment for glaucoma.

Medical cannabis contains two primary cannabinoids known for their therapeutic and medicinal applications:

  • THC stimulates the CB1 and CB2 receptors in the brain and causes a feeling of euphoria. THC also has analgesic properties, which means it can reduce pain.
  • CBD is a cannabinoid known for its therapeutic and medicinal applications. It stimulates the CB2 receptor and has been shown to reduce inflammation, decrease anxiety, and potentially treat cancer cells.

These cannabinoids influence the endocannabinoid system’s activity, which is responsible for regulating a wide range of physiological processes. The endocannabinoid system has receptors in the eye and other tissues that respond to the cannabinoids found in cannabis.

How medical cannabis may help glaucoma

Medical cannabis is an increasingly popular treatment option for glaucoma. Studies have shown that cannabis may reduce intraocular pressure (IOP), which is one of the primary risk factors for developing the disease. In addition to lowering eye pressure, medical cannabis can also reduce inflammation and oxidative stress, leading to increased IOP.

Medical cannabis oil may lower eye pressure, but research is still conflicting.

There is conflicting data on the effects of cannabis on intraocular pressure. Some studies have shown that patients with glaucoma who use medical cannabis experience a reduction in eye pressure, while others show no effect.

For instance, a 2019 review published in the Diabetes & Metabolism Journal found evidence that medical cannabis may help lower IOP. However, there is only limited evidence for this effect. The authors noted that most studies were small and had methodological flaws or limitations.

In an older 2006 study published in the Journal of Glaucoma, researchers found that 5mg of THC significantly reduced IOP after two hours. The same study found that a low dose of CBD did nothing, but a higher dose (40mg) led to a small IOP increase within four hours.

One problem with THC treatment is the amount a patient needs to take to achieve the desired effect. The 2006 study found that 5mg of THC reduced IOP by only 0.3mmHg, which is not considered a clinically significant change. In other words, you would need to take quite a bit of medical cannabis to achieve any measurable benefit for glaucoma patients. The needed THC dose will disrupt daily life.

THC may reduce IOP, but also reduce the blood pressure within the optic nerve. This effect can be problematic for patients with glaucoma who already have impaired blood flow to the optic nerve.

Medical CBD for glaucoma may reduce inflammation

In a 2021 study published in the International Journal of Molecular Sciences, researchers found that CBD may help treat glaucoma. CBD’s effect on eye conditions lies in its anti-inflammatory and antioxidative properties.

Inflammation and oxidative stress caused by free radicals can lead to increased IOP. The endocannabinoid system (ECS) is normally involved in regulating inflammatory responses. CBD acts on CB receptors to modulate inflammation, which can help reduce IOP.

Nevertheless, CBD may have conflicting roles in increasing or decreasing IOP. Some studies suggest that dosage matters – a high CBD dose can lead to negative outcomes. Still, it remains unclear how CBD impacts eye pressure.

Medical CBD has antioxidative properties

Oxidative stress is a condition in which the body has too many free radicals, which can cause damage to cells. It is well known that oxidative stress can lead to eye diseases such as age-related macular degeneration (AMD) and more.

In a 2021 study published in Neuropharmacology, researchers found that CBD can help the retina against damage caused by oxidative stress. Oxidative stress is one of the main causes of glaucoma. This finding could be especially promising for people with this disease.

The authors also explain that CBD decreases inflammation and helps protect cells from free radicals. These effects may also help prevent or delay oxidative damage and other harmful effects on neural tissue.

Medical CBD oil for glaucoma prevents glutamate spillover

Glutamate is an amino acid that plays an important role in the human body. It’s a neurotransmitter that helps relay messages between nerve cells, but too much of it can cause damage to your brain cells. Glutamate spillover can also increase inflammation and oxidative stress.

People with glaucoma have higher levels of glutamate in their eyes than those without the disease, which could be why CBD could be effective at treating this condition. A 2021 study published in the International Journal of Molecular Sciences suggests that CBD can help dampen the release of the neurotransmitter in brain synapses.

Should I take medical cannabis for glaucoma with other medications?

If you are taking other medications, talk to your doctor about whether medical cannabis is safe. Doctors generally recommend that patients avoid using cannabis with sedatives, antidepressants and opiates.

Patients with a history of psychosis should avoid medical cannabis oil that contains THC. Pregnant or breastfeeding women should not use medical cannabis.

CBD options are generally well-tolerated, even at higher doses. Still, make sure to follow the recommended dose of medical cannabis. Do not mix medical cannabis with alcohol or medications without consulting your physician first.

Alternative treatment options for glaucoma

Mature woman examining eyes in front of a mirror while touching her temples

Lifestyle changes can also lead to an improvement in symptoms:

  • Quitting smoking and reducing alcohol consumption are good ways to lower your risk of developing glaucoma.
  • Reducing stress can also be beneficial since chronic stress can lead to elevated pressure in the eye, particularly in angle-closure glaucoma.
  • Decreasing caffeine consumption can lead to better outcomes as the substance can cause an increase in IOP.
  • Regular exercise has been shown to reduce eye pressure

Other herbal remedies like bilberry extract also show promise in lowering eye pressure. Studies have also shown that a specific type of omega-3 fatty acid called EPA (eicosapentaenoic acid) can help slow the progression of glaucoma.

Conclusion

Medical cannabis remains a controversial treatment option for glaucoma. While cannabis may help lower IOP, many questions remain about which cannabinoid/s and how much should be administered.

THC can help reduce eye pressure. CBD can help prevent inflammation and oxidative stress. However, further research is needed to make medical cannabis oil for glaucoma treatment a viable option. Always consult with a doctor. 

At Lyphe, we provide a safe and professional environment. Our team of expert doctors will help you determine if medical cannabis is right for your eye condition. Contact us today to schedule an appointment!

Frequently Asked Questions (FAQs)

Does cannabis relieve glaucoma?

Medical cannabis oil may help treat glaucoma based on early clinical findings. However, the data is still conflicting, and more research is needed.

How can I reverse glaucoma naturally?

Glaucoma is a condition that cannot be reversed, but it can be managed through medication and/or surgery. If left untreated, glaucoma can lead to vision loss and blindness.

Does CBD elevate eye pressure?

A 2018 study found that CBD oil-based eye drops elevated eye pressure in lab mice. However, the rise in eye pressure may not necessarily be dangerous as it may be controlled.

How can I lower my eye pressure?

Lifestyle changes like exercising regularly and reducing stress can help reduce eye pressure. You should also eat a diet rich in omega-3 fatty acids (e.g., salmon, tuna and sardines) to keep ocular blood flow healthy.

Can CBD oil make glaucoma worse?

Some evidence shows that CBD may increase intraocular pressure (IOP), which can worsen glaucoma. However, there’s also evidence that CBD may help reduce IOP in some cases.

References

https://www.mdpi.com/1422-0067/22/7/3798/htm

https://www.medicalnewstoday.com/articles/marijuana-and-glaucoma

https://pubmed.ncbi.nlm.nih.gov/16988594

https://dalspace.library.dal.ca/bitstream/handle/10222/78955/9830-17586-1-SM.pdf

https://www.mayoclinic.org/diseases-conditions/glaucoma

https://www.ncbi.nlm.nih.gov/books/NBK224386/

https://iovs.arvojournals.org/article.aspx?articleid=2718702

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1358964/

Author: Bojan
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Bojan Ambrus, Head of Marketing & Digital Product at Lyphe Group, is a data-driven growth marketing professional with over 15 years of rich experience. His background includes roles such as Head of Marketing at Vaping.com and growth marketing roles in various enterprises, startups, and scale-ups. His expertise in building and positioning businesses is particularly valuable in the cannabis sector, where he navigates its complexities and regulatory challenges. His strategic marketing insights make Bojan a key player in shaping Lyphe Group's marketing and digital product strategies.

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