– Ed

The Law

South Africa’s Constitutional Court has passed down a judgment that makes it legal for adults to cultivate and smoke cannabis in their homes. The country’s highest court ruled that the right to privacy was violated by prohibiting the possession, purchase, or cultivation of cannabis for personal consumption by an adult in a private dwelling. Nevertheless, perceptions and attitudes regarding marijuana use continue to evolve with increasing interest in its therapeutic potential.

Can Marijuana Lower Intraocular Pressure?

Marijuana’s ability to lower intraocular pressure (IOP) was discovered in the 1970s. Elevated IOP is the major risk factor for glaucoma and lowering IOP is currently the only treatment. Doctors and scientists have wondered whether marijuana could be used as a therapy to
lower IOP and prevent the progression of glaucoma. Naturally, this would be of interest to glaucoma patients.

While marijuana does lower IOP, it has major drawbacks as a treatment for a chronic, long-term, disease like glaucoma. Conventional glaucoma eyedrops can be effective for up to 24 hours, whilst smoking cannabis reduces eye pressure for only 3-4 hours. To control IOP would require 8-10 doses of marijuana per day. This would not only cost more than conventional glaucoma treatment, but the physical and mental side-effects of frequent marijuana use would prevent functioning productively. For example, while users may enjoy its euphoric effects, marijuana also impairs judgment and coordination, increases paranoia, elevates heart rate, and irritates the eyes.

Long-term Safety Concerns

Concerns also exist regarding the long-term safety of marijuana use, due to its associations with permanent lung damage when smoked, and possible lasting 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. Finally, the lack of regulation and quality control makes efficacy and safety of marijuana unpredictable.

Research efforts to develop Tetrahydrocannabinol (THC) eyedrops that can effectively lower eye pressure while minimising side effects are underway but have not yet been successful. For these reasons, while marijuana does lower eye pressure, it is not recommended as a medical treatment for glaucoma. If you use cannabis, let your Eye Care Practitioner know since it may have an impact on your eye pressure readings. Also, it is very important to continue your current glaucoma therapy and regular monitoring as recommended by your ophthalmologist.

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