Glaucoma is among the most frequently listed qualifying conditions for the use of medical cannabis, along with cancer, chronic pain, epilepsy, arthritis, PTSD, and Alzheimer’s disease, among others.
But what is glaucoma and how does medical cannabis help in its treatment?
Glaucoma: What is it?
Glaucoma is a common eye condition that gradually causes damage to the optical nerves and therefore reduces side vision. One cause for optic nerve damage among glaucoma patients is high pressure within the eye — called intraocular pressure or IOP.
The optic nerves are the ones in charge of transmitting images to the brain.
When left untreated, glaucoma can lead to blindness. In fact, it is one of the leading causes of irreversible blindness globally, affecting over 60 million people.
What causes glaucoma?
Glaucoma tends to be hereditary and may not manifest until later in life. This is why glaucoma most often affects the elderly.
Glaucoma occurs when the optic nerves gradually get damaged due to the increased IOP brought by fluid buildup. High fluid pressure takes place on the front part of the eye.
The fluid, called aqueous humor, normally flows out of the eye through a mesh-like channel called the trabecular meshwork. A blockage in this channel would cause fluid buildup.
The exact cause for this blockage is not known, but scientists say that it can be inherited and can be passed from parents to their children. Other (less common) causes include severe eye infection, chemical or blunt injury to the eye, inflammatory conditions, and blocked blood vessels in the eye.
Rarely, glaucoma can also be caused by eye surgery done to correct another eye condition. Glaucoma usually affects both eyes, but can be worse in one eye than the other.
Two types of glaucoma
There are two main forms of glaucoma. One is open-angle or wide-angle glaucoma, which is the most common type. This is when the drain structure in the eye or the trabecular meshwork looks normal but fluid does not flow out they way it should.
The other one is angle-closure glaucoma. It is also called chronic angle-closure, acute angle-closure, or narrow-angle glaucoma. This happens when your eye does not drain properly because the drain space between the cornea and the iris becomes too narrow. This, in turn, causes a sudden pressure buildup in the eye. This is also linked to cataracts and farsightedness.
Cataracts is the clouding of your eye’s lens.
Who’s more likely to get glaucoma?
Glaucoma mostly affects people who are over 40 years old. However, it is possible for young adults, teenagers, children, and even infants to have it, too.
According to statistics, you are more likely to get glaucoma if you are of African-American, Russian, Irish, Hispanic, Japanese, Scandinavian, or Inuit descent.
Those who have diabetes and those with poor vision are also more likely to get the ailment, as well as those who have had eye trauma and those who take certain steroid medications like prednisone.
Symptoms of glaucoma
How do you know that you may have glaucoma? The truth is, most people do not have symptoms.
The first sign of glaucoma is the loss of side or peripheral vision. But this can go unnoticed until it is already late in the disease.
This is the reason why glaucoma is often referred to as the “sneak thief of vision.”
In order to detect glaucoma early, one should undergo a complete eye exam every one to two years.
Sometimes, IOP can also rise to severe levels, and if this happens, one may experience headache, blurred vision, sudden eye pain, or the appearance of halos around lights. In case you notice any of these symptoms, you have to seek immediate medical care.
Other symptoms include redness in the eye, vision loss, hazy-looking eyes, nausea or vomiting, and narrowed or tunnel vision.
Conventional treatment for glaucoma
Glaucoma is usually treated using prescription eye drops, laser eye surgery, or microsurgery to lower IOP.
The eye drops are formulated to lessen the formation of fluid.
For those with open-angle glaucoma, the laser surgery slightly increases the flow of fluid from the eye. For those with angle-closure glaucoma, the procedure can stop fluid blockage.
More specifically, the different types of laser surgery procedures include:
- Trabeculoplasty, which opens the drainage area
- Iridotomy, which makes a tiny hole in the eye’s iris to allow the fluid to flow more freely
- Cyclophotocoagulation, which treats the eye’s middle layer areas to reduce fluid buildup
As for microsurgery, a procedure called trabeculectomy creates a new channel for the fluid to drain, therefore easing eye pressure. Sometimes, however, this surgery fails and needs to be redone. The doctor might implant a tube in order to help drain the fluid.
Surgery is quite risky, though, because it can cause temporary or permanent vision loss, bleeding, or infection.
How does cannabis help treat glaucoma?
As early as the 1970s, research has found that cannabis and THC can reduce IOP and thus alleviate glaucoma-related symptoms.
In fact, one of the first studies on cannabis and glaucoma has found that smoking pot can lower IOP by 20-30 percent.
However, researchers also found in later studies that cannabis can only temporarily reduce IOP. More specifically, the effects of cannabis only lasts a few hours — three to four houses — and this is one of the reasons why the drug is not considered by ophthalmologists as the best treatment option for glaucoma.
The problem with this is that glaucoma needs around-the-clock treatment. This means that one would have to smoke pot for a total of six to eight times a day, over the course of 24 hours in order to achieve consistently low IOP levels. Yet, because of THC’s mind- and mood-altering effect, this might not be convenient. What’s more, this frequency in pot consumption could increase one’s risk of developing cannabis use disorder.
However, when it comes to glaucoma that’s already in the late stages, ophthalmologists are more open to a cannabis-based treatment. With late-stage glaucoma, it is less about targeting the glaucoma directly and more about relieving the patient of the accompanying symptoms, such as pain and nausea.