Glaucoma is the word used to describe multiple eye conditions that are characterized by damage to the optic nerve caused by a build up in eye pressure. The optic nerve is responsible for sending visual information from the eye to the brain. This disorder causes patients to develop a reduced field of vision that can lead to blindness. Glaucoma is incurable and the second leading cause of blindness in the world, according to the World Health Organization.
The Glaucoma Research Foundation states that there are 60 million people suffering from glaucoma throughout the world, and 2.7 million of those people reside in the United States.
Only about half of the people suffering from glaucoma even know that they have it. This disease is often called the “silent thief of sight” because the vision loss develops slowly over time, and symptoms often go unnoticed until the disease is in advanced stages. Glaucoma can only be detected by an eye doctor through a comprehensive dilated eye exam.
There are actually several different types of glaucoma, but only two types are common. Most forms are very rare with all other types combined accounting for only 10 percent of all diagnosis. The two that occur most often are characterized by an increase in intraocular pressure (IOP), or pressure inside the eye (shown in the diagram below), which damages the optic nerve. The cause of the increase in eye pressure is similar, but different between the two most common types.
The 2 Most Common Types of Glaucoma:
1. Open-Angle Glaucoma
Open-angle refers to the angle where the iris meets the cornea (location marked by the red x’s in the diagram above, and marked “angle where the canals are located” in the diagram below). In eyes diagnosed with this form of glaucoma, the angle is normal, meaning it is as wide and open as it should be. There is a nourishing, gelatinous eye fluid called “aqueous humor” that normally drains through the microscopic passageways of this angle into the ocular cavity. Open-angle glaucoma causes blockage in this area which results in slower fluid draining. This clogging of the optic nerve’s drainage canals results in a build up or increase in eye pressure.
The eye pressure damages the optic nerve and reduces field of vision. It is a life-long condition that develops and worsens slowly over time.
This type often produces few to zero early-onset symptoms in sufferers, and therefore will go unnoticed and un-diagnosed for many years, facilitating vision loss.
- Gradual loss of peripheral vision, usually in both eyes – this symptom often goes unnoticed because the vision lost can be compensated by simple turning the head.
- Tunnel vision (in advanced stages)
2. Acute Closed-Angle Glaucoma (angle-closure)
This type, also known as narrow-angle glaucoma, is caused when the angle between the iris and cornea is closing, or is more narrow than it should be. Therefore the drainage canals become blocked, and cause a sudden increase in intraocular pressure. This type of glaucoma develops quickly, and results in suddenly noticeable symptoms and damage. This form usually requires immediate medical attention.
- Eye pain
- Nausea and vomiting
- Rainbows or halos around lights at night
- Blurred vision
- Sudden onset of visual disturbance
For all forms of glaucoma, if the word “primary” is used before the type, it means that cause of the condition is unknown (e.g. primary open-angle glaucoma). The word “secondary” is used if the cause, such as an eye injury, is known (e.g. secondary open-angle glaucoma).
Can cannabis therapies be used to treat glaucoma?
Although cannabis does not cure glaucoma, it can be helpful in reducing symptoms of the condition, but in some cases it can also produce a negative result.
A study published in 1979, Effects of tetrahydrocannabinol on arterial and intraocular hypertension, showed that smoking marijuana can cause a decrease in the damaging eye pressure. In some cases, however, it can also lower blood pressure which could result in not enough blood flowing to the optic nerve. In those cases, the benefit experience from smoking cannabis is canceled out because not enough blood flow to the optic nerve is also damaging.
It seems that while smoking dried marijuana flowers may not be the best option for treating glaucoma, targeted cannabinoid therapies could be successful, but more research is necessary to be conclusive. Smoking, eating or vaporizing cannabis flowers is not ideal because it provides temporary relief of only a few hours at a time, when to be treated properly, the eye pressure needs to be reduced twenty-four hours per day.
Smoking cannabis flowers may also produce psychoactive effects in a patient, which may not be ideal for those who have to go to work or just do not like the way it feels. The psychoactive cannabinoid, THC, however is beneficial in temporary treatment of symptoms such as nausea and vomiting caused by acute-closed angle glaucoma, so smoking the plant could provide temporary symptom relief in some patients.
More research needs to be conducted on this topic to make any hard evidential conclusions about cannabis therapy being used to treat glaucoma. Due to marijuana currently being classified as a Schedule I drug under the Controlled Substances Act, research and clinical studies have been limited due to the lack of access scientists have to the plant.
More research could identify exactly which cannabinoids and terpenes found in marijuana are beneficial as therapy or treatment, and which are not. There are more than 80 different cannabiniods found in the cannabis plant, but scientist know very little about the majority of them. There is evidence that different cannabinoids can produce many different beneficial effects in people, however, such as anti-inflammatory, anti-tumor, anti-septic, anti-pain, anti-seizure and much more. For example, in a 2009 study the cannabinoid, cannabigerol (CBG) has been shown to increase fluid drainage and reduce pressure, but scientists do not yet know how to target this specific cannabinoid. If that research could be completed, then targeted cannabinoid therapies could potentially be developed. Targeting specific cannabinoids could even exclude the psychoactive effects all together, and allow for more consistent treatment.
In conclusion, cannabis therapy could be beneficial in the treatment of glaucoma, but it would be on a case-by-case basis. It is not recommended to self-medicate with marijuana without first consulting a physician because depending on the type of glaucoma, it could do more harm than good if it results in extreme lowering of blood pressure.