Glaucoma is a frightening disease because it often appears to affect victims out of nowhere. By the time it starts causing symptoms like blurriness, nausea, and loss of peripheral vision, it has already done considerable damage to the optical nerve, causing permanent loss of vision.
Fortunately, the buildup of intraocular pressure (IOP) that causes glaucoma can be treated, preventing further vision degradation. While cannabis can temporarily reduce pressure, it’s generally not used as a first-line treatment for glaucoma. However, it may be useful in some cases. Here’s what we know.
The Basics of Glaucoma
Your body constantly pumps a transparent fluid called aqueous humor into your eye. This fluid maintains the shape of the eyeball and provides nutrients to various structures inside your eye. Normally, excess fluid drains out, maintaining the correct intraocular pressure. However, when one or both of the structures responsible for draining the eyeball become blocked, the pressure increases.
This doesn’t immediately cause symptoms, and if you catch glaucoma quickly (through regular eye exams), your doctor may be able to prevent damage. However, over time it can damage the optic nerve that feeds images from your eye to your brain, damaging your vision or even causing complete blindness if left untreated.
Treatment for glaucoma focuses on controlling optical pressure through medications and/or surgery. If the treatment can keep your IOP at a healthy level, it should prevent further damage from glaucoma.
Cannabis and Glaucoma: What We Know
Cannabis was first shown to have an effect on IOP in a 1971 study. The study, Marihuana [sic] Smoking and Intraocular Pressure showed that smoking cannabis could lower IOP by 30 percent, for three to four hours. Interestingly, this effect works when THC and other cannabinoids are consumed in the traditional way.
Taking cannabis internally by smoking, vaporizing, eating supplements or using tinctures will lower IOP. However, cannabis in eye drops, rubs, and other external treatments will not have that effect.
Scientists don’t yet understand how cannabis reduces IOP, but THC — the psychoactive component — is believed to be a key ingredient. CBD, a non-psychoactive cannabinoid responsible for many of cannabis’ health benefits, hasn’t been proved to treat glaucoma, and at least one study showed that CBD itself may actually increase IOP. Research on cannabinoids is ongoing, and it’s certainly possible that there are additional ways cannabis could help glaucoma in the future, but for most patients, it’s currently not the preferred treatment.
Cannabis vs. Modern Glaucoma Treatments
When scientists first discovered the effect of cannabis on glaucoma, it was an exciting breakthrough. There were few treatments available, and many of them had serious side effects, which could potentially be avoided by using cannabis instead.
However, glaucoma treatment has progressed since then. There are now modern drugs with low side effects that can stabilize IOP when taken just once or twice a day. Additionally, there are various surgical treatments that can help the eyes drain, with little risk to the patient, including a non-invasive laser surgery that opens the trabecular meshwork — the sole part of the eye that becomes blocked in the most common form of glaucoma.
Cannabis, by contrast, needs to be taken 6 to 8 times per day to maintain IOP. Not only is it difficult to take a drug every 3 to 4 hours, but it also means you’ll be constantly intoxicated with THC, which many people will find disruptive. Additionally, cannabis can lower blood pressure, which could actually harm the damaged ocular nerve.
Circumstances Where Cannabis May Benefit Glaucoma Patient
All treatments involve trade-offs, and there are scenarios where it makes sense to treat glaucoma with cannabis. Glaucoma primarily affects older people, who have a higher risk of conditions like arthritis and chronic pain, where cannabis can be of great benefit, and also treat glaucoma as a side benefit. There may also be circumstances where the patient can’t take conventional treatments, such as a risk of harmful drug interactions or serious side effects. In those cases, cannabis might be the best option available.
Ultimately, it’s up to you and your doctor to weigh the different options for treatment and pick the one with the least risks/side effects, and the best chance of success. However, you should not experiment with alternative glaucoma treatments on your own — you won’t know treatment isn’t working until you experience further vision decline in which case it may be too late. Only your doctor can test and monitor your IOP, and adjust your medication to protect your vision.