Marijuana and glaucoma became inextricably linked back in 1976 when Robert Randall became the first patient to be granted access to medical cannabis for the condition. He had accidentally discovered that his intraocular pressure dropped when he smoked marijuana and petitioned to be allowed to legally use the drug to prevent him from going blind.
Ever since, countless numbers of people have used medicinal marijuana for glaucoma, but is there any evidence that it’s an effective treatment for the disease?
What Is Glaucoma?
Glaucoma can be a devastating condition for those who suffer from it. The condition is caused when the aqueous humor, or fluid in the eye, can’t drain properly and builds up, causing the intraocular pressure to increase. Depending on the type of glaucoma, the disease can cause eye pain, halo affects around lighting, nausea, and vomiting.
Left untreated, an increase in eye pressure can damage the optic nerve and create a gradual loss of vision. Unfortunately, by the time most people experience symptoms of glaucoma, some degree of eye damage has already been done.
Medical Treatments for Glaucoma
If glaucoma is detected early, steps can be taken to prevent damage to the eye. The least intrusive methods of treatment are prescription medications, with surgery being an option if those don’t lessen symptoms.
Patients often manage their glaucoma by taking eye drops each day. Eye drops work topically to help the eye drain better or to help reduce the amount of aqueous humor (fluid produced by the eye). Eye drops can cause side effects that range from stinging and itching to fatigue and shortness of breath. Because they enter the bloodstream, they can also interact with other medications.
If drops don’t work well at controlling eye pressure, pills are used to help further control the production of fluid. Pills tend to have more systemic side effects than drops and have to be taken three to four times daily. Drug interactions are also a concern with oral glaucoma medications, so it’s important for healthcare providers to carefully monitor what other medications their glaucoma patients are taking. Side effects can include tingling of extremities, fatigue, memory problems, and more.
In patients for whom medications don’t work or aren’t tolerated, surgery may be an option. Some patients may also opt for surgery as their first treatment option; if intraocular pressure can be lowered with surgery, then daily drops, pills, and their associated side effects might be avoided for the time being. There are several different forms of eye surgery for glaucoma, all of which work to alter the eye’s drainage system so the fluid can drain properly. Surgery isn’t permanent, however, so patients will typically have to seek treatment via medication once eye pressure begins to build once more.
Marijuana and Glaucoma
Among the many health benefits of cannabis, patients and researchers have discovered that it can lower intraocular pressure. Some glaucoma sufferers who are seeking relief have turned to cannabis to help reduce their symptoms and control the disease. With medical marijuana becoming legally available in an increasing number of places throughout the world, it’s worth taking a look at the mechanisms through which it works to relieve symptoms. It’s also important to consider the reasons why many healthcare professionals still don’t recommend marijuana as a first-line treatment for glaucoma.
Research on Glaucoma and Marijuana
Scientists have been looking at cannabis as a possible glaucoma treatment for many years. A 1971 study showed that cannabis could lower the intraocular pressure in glaucoma patients. Participants who smoked cannabis experienced an increase in heart rate and then a decrease in blood pressure as well as intraocular pressure. This was a promising result for those with glaucoma. However, the results were concerning for those with heart conditions in which an increased heart rate could be dangerous. Also problematic were side effects that might make it hard for subjects to go about their day; euphoria, cognitive impairment, short-term memory loss, sleepiness, and reduced coordination were common.
THC and Glaucoma
After learning that cannabis was good at lowering intraocular pressure, researchers set out to learn which cannabinoids (or active ingredients) in the plant were responsible for doing this. The National Eye Institute conducted a study specifically looking at the THC/tetrahydrocannabinol in cannabis to see if it was the pressure-lowering cannabinoid. Researchers found this to be the case, but they also found that THC only works for a few hours. Because of this, they determined that dosing throughout the day was necessary to keep eye pressure levels steady.
As with the 1971 study, scientists found that the THC that causes eye pressure to drop also creates the psychoactive effects of marijuana, making it difficult for people to dose before driving, working outside of the home, and going about many typical daily activities. Scientists continued to experiment with cannabis in various forms, as well as using different methods of delivery.
In 1981, researchers developed mineral oil drops containing a lower level of THC than the cannabis used by the smoking study. The drops could be applied directly to the eyes. They found that the THC could lower systolic blood pressure and intraocular pressure without increasing heart rate. The biggest plus? The effects lasted anywhere from 8 to 12 hours.
Intraocular Cannabinoid Receptors
Studies have continued over the years, with researchers testing out various strains and cannabis compounds. They have discovered that there are cannabinoid receptors inside the eye that may respond to topical application of cannabis compounds in the treatment of glaucoma. They have also discovered that these receptors control help control intraocular pressure because they are responsible for regulating levels of fluid inside the eye. What all of this means for treatment remains to be seen, but it does point to the potential of cannabis-based topical glaucoma treatments that can be applied directly with fewer systemic effects.
Does Marijuana Help Glaucoma?
In the meantime, patients who use cannabis to treat their glaucoma report that it helps decrease their eye pain. Because it reduces the pressure inside the eye, it can be used to prevent the disease from progressing, which is important because eye damage has already occurred by the time the first symptoms become noticeable. Because cannabis is now available in a variety of strains and different forms of ingestion, patients using it for medical purposes can take it more conveniently and avoid some of the side effects that can occur with smoked cannabis. It’s important for patients to understand that like prescription drops or pills, cannabis doesn’t reverse or cure the disease but can help keep eye pressure levels low while staving off symptoms such as pain, nausea, and vomiting.
Concerns About Marijuana for Glaucoma
While studies into using cannabis for glaucoma have been promising and many patients are using it to find relief from their symptoms, there are specific reasons why most healthcare providers avoid recommending marijuana as a first choice for treatment.
Optic Nerve Damage
A major concern that healthcare professionals in the glaucoma field have about cannabis as a treatment for the disease is that it lowers the blood pressure within the eye, therefore decreasing blood supply to the optic nerve. Many experts say that this can cause damage to an already-stressed optic nerve. Because the point of glaucoma treatment is to stop the progression of eye damage, this makes cannabis a double-edged sword of a treatment. While it can lower eye pressure and works well as a painkiller, it could also potentially speed along the process of vision loss.
Method of Delivery
Another concern with using medicinal marijuana for glaucoma is finding an effective method of delivery. The pressure-lowering effects of inhaled cannabis wear off quickly, while oral cannabis is unpredictable in terms of absorption. Topical preparations such as eye drops would be ideal, except they have a hard time penetrating intraocular tissues in order to deliver their active ingredients.
Health and Medications
For those who do choose to proceed with using cannabis as a treatment for glaucoma, there are other factors to keep in mind. Those with heart conditions should check with their doctors before starting a medical cannabis regime, as the fluctuations in heart rate and blood pressure could be dangerous for some. Cannabis can also react with certain medications, so doctors should check for potential drug interactions. It’s very important to receive advice and guidance from a healthcare professional when treating any sort of chronic disease, even for patients living in areas where medical marijuana isn’t legal and who plan to self-medicate.
CBD and Glaucoma
If whole-plant cannabis and THC have positive effects on eye pressure, what about taking CBD oil for glaucoma? CBD (cannabidiol) has been shown to have anti-inflammatory, antioxidant, and neuroprotective properties that could be useful in glaucoma treatment, but it’s unclear what benefits CBD has beyond reparative and protective properties.
While THC lowers intraocular pressure, CBD doesn’t seem to have the same effect. In fact, a study in which subjects were given sublingual CBD showed that a CBD dose of 20 mg has no effect on intraocular pressure, while a dose of 40 mg actually causes pressure to increase. Because THC has been proven to lower intraocular pressure and CBD has healing and protective properties, the evidence points to a carefully-proportioned THC/CBD combination as being the best cannabis-based treatment for glaucoma.
Patient Education is Essential
As more research is done and marijuana becomes more readily available, scientists are exploring ways to use marijuana to target the eye in a way that doesn’t affect the optic nerve or increase intraocular pressure. At the moment, most eye experts recommend pharmaceutical treatments and surgery as a first-line defense and only suggest marijuana for glaucoma as a treatment for advanced cases of the disease.
Because research into glaucoma and marijuana is ongoing, it’s essential for patients to educate themselves and keep up-to-date on the latest findings. While using cannabis or CBD oil for glaucoma seems promising, reading up and understanding how marijuana works inside the eye is important to ensure that the condition is carefully controlled and not exacerbated.
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