Marijuana can cause permanent lung damage when smoked, and possible permanent adverse effects on cognition and mental health. With regular use, tolerance to the eye pressure-lowering effects develops, meaning that increasing drug levels would be required to prevent progression of glaucoma. Moreover, lack of regulation and quality control makes efficacy and safety of marijuana unpredictable. Research efforts to develop THC eyedrops that can effectively lower eye pressure while minimizing side effects are being studied, but have not yet been successful.
New evidence has emerged showing that parts of the cannabis plant, specifically cannabidiol (CBD), the non-intoxicating, trendy component, may actually worsen glaucoma symptoms. Researchers at Indiana University published a study in the journal Investigative Ophthalmology & Visual Science that shows CBD increases pressure in the eye. This is problematic, they say, considering that CBD has become such a household name in American culture that many people, some of which may have or be at risk for glaucoma, are using it haphazardly as a natural, harmless medicine. But in reality, CBD could be destroying their overall eye health.
While marijuana does lower IOP, it has major drawbacks as a treatment for a chronic, long-term, disease like glaucoma:
What About CBD (cannabidiol) Oil?
As marijuana use becomes more accepted and increasingly legalized, glaucoma patients frequently ask if marijuana can really treat glaucoma. We need to explain some truths and dispel some myths.
Marijuana is legal for medical use in 30 US states and for recreational use in 9 US States. It’s legal across Canada for recreational use. Despite the relaxed attitude around marijuana, it is still classified by the federal Drug Enforcement Agency as a Schedule I controlled substance (the same category as heroin and LSD ).
Marijuana’s ability to lower intraocular pressure (IOP) was discovered in the 1970s. Elevated IOP is the major risk factor for developing glaucoma and for the progression of glaucoma. Treatment is focused solely on reducing IOP. Many have wondered whether marijuana could be used as a therapy to lower IOP and prevent glaucoma from getting worse or causing blindness.
For these reasons, smoking marijuana or using CBD oil is not recommended as a medical treatment for glaucoma. If you use marijuana or CBD oil, let your ophthalmologist know since it may have an impact on your eye pressure readings. Also, it is very important to continue the glaucoma treatment recommended by your ophthalmologist. This treatment and regular monitoring can help you maintain your vision for the rest of your life.
Results: Two hours after sublingual administration of 5 mg Delta-9-THC, the IOP was significantly lower than after placebo (23.5 mm Hg vs. 27.3 mm Hg, P=0.026). The IOP returned to baseline level after the 4-hour IOP measurement. CBD administration did not reduce the IOP at any time. However, the higher dose of CBD (40 mg) produced a transient elevation of IOP at 4 hours after administration, from 23.2 to 25.9 mm Hg (P=0.028). Vital signs and visual acuity were not significantly changed. One patient experienced a transient and mild paniclike reaction after Delta-9-THC administration.
Patients and methods: A randomized, double-masked, placebo-controlled, 4 way crossover study was conducted at a single center, using cannabis-based medicinal extract of Delta-9-THC and CBD. Six patients with ocular hypertension or early primary open angle glaucoma received a single sublingual dose at 8 AM of 5 mg Delta-9-THC, 20 mg CBD, 40 mg CBD, or placebo. Main outcome measure was IOP. Secondary outcomes included visual acuity, vital signs, and psychotropic effects.
Purpose: The purpose of this study was to assess the effect on intraocular pressure (IOP) and the safety and tolerability of oromucosal administration of a low dose of delta-9-tetrahydrocannabinol (Delta-9-THC) and cannabidiol (CBD).
Conclusions: A single 5 mg sublingual dose of Delta-9-THC reduced the IOP temporarily and was well tolerated by most patients. Sublingual administration of 20 mg CBD did not reduce IOP, whereas 40 mg CBD produced a transient increase IOP rise.
Research such as that by Tomida et al, 3 however, suggests that the mixed results of earlier studies with regard to the effect of cannabis on IOP may be related to the use of various strains with differing proportions of THC and CBD. Future studies investigating cannabis and IOP lowering should therefore specify the strain and THC/CBD composition to best assess therapeutic potential.
Tomida and colleagues performed a randomized, double-masked, placebo-controlled crossover study of six patients with ocular hypertension or mild primary open-angle glaucoma. 3 After washout of their usual topical IOP-lowering regimen, patients were randomly assigned to treatment with sublingual THC, lower-dose (20 mg) sublingual CBD, higher-dose (40 mg) sublingual CBD, or placebo. Two hours after treatment was administered, compared to placebo, patients who had received THC experienced a modest decrease in IOP, whereas those who had received the higher dose of CBD experienced a slight increase in IOP.
4. Miller S, Daily L, Leishman E, et al. ∆9-tetrahydrocannabinol and cannabidiol differentially regulate intraocular pressure. Invest Ophthalmol Vis Sci. 2018;59(15):5904-5911. doi:10.1167/iovs.18-24838
3. Tomida I, Azuara-Blanco A, House H, Flint M, Pertwee RG, Robson PJ. Effect of sublingual application of cannabinoids on intraocular pressure: a pilot study. J Glaucoma. 2006;15(5):349-353. doi:10.1097/01.ijg.0000212260.04488.60
7. Kabiri M, Kamal SH, Pawar SV, et al. A stimulus-responsive, in situ-forming, nanoparticle-laden hydrogel for ocular drug delivery. Drug Deliv Transl Res. 2018;8(3):484-495. doi:10.1007/s13346-018-0504-x