What topics does this cannabis study cover?

This study covers research on: Pain.

THC lowers eye pressure but falls short compared to existing glaucoma drugs

Q: What did this research study find?

This systematic review and meta-analysis examined how *tetrahydrocannabinol* (**THC**) affects intraocular pressure (IOP), a key factor in glaucoma development. Researchers analyzed five clinical studies involving 99 patients to pool together evidence about THC's pressure-lowering effects. Their fin

Q: Where was this research published?

Published in Canadian journal of ophthalmology. Journal canadien d'ophtalmologie on May 1, 2026.

Intraocular pressure-lowering effects of tetrahydrocannabinol drugs: a systematic review and meta-analysis.

Canadian journal of ophthalmology. Journal canadien d'ophtalmologie • May 1, 2026 • Moderately Relevant

🤖

AI Summary

This systematic review and meta-analysis examined how tetrahydrocannabinol (THC) affects intraocular pressure (IOP), a key factor in glaucoma development. Researchers analyzed five clinical studies involving 99 patients to pool together evidence about THC's pressure-lowering effects. Their findings showed that THC reduced IOP by approximately 14.66% overall, with IV administration producing the most dramatic effect at 33.27% reduction. However, when comparing THC to control treatments, the differences were much less impressive—only a 6.88% reduction that wasn't statistically significant.

The route of administration made a substantial difference in effectiveness. Intravenous THC showed the strongest results, while oral and topical routes produced minimal, non-significant reductions of around 9-10%. This finding is particularly important for patients considering cannabis as a glaucoma treatment, since smoking or oral consumption may not provide the pressure-lowering benefits seen with IV administration in clinical settings. The study also highlights a crucial limitation: while THC does lower IOP, it performs comparatively poorly against conventional glaucoma medications when head-to-head comparisons were made.

These results suggest that THC may have only limited practical value as a standalone glaucoma therapy, especially through commonly accessible routes like smoking or oral ingestion. While the initial finding of IOP reduction might sound promising, the comparison to existing treatments and the modest effects through practical delivery methods indicate that THC is unlikely to replace current glaucoma medications. Future research would need to develop more effective delivery methods or combination approaches to make cannabis-based treatments genuinely competitive for this application.

📄 Original Abstract

Within the past few decades, several studies have reported intraocular pressure (IOP)-lowering effects associated with tetrahydrocannabinol (THC) compounds as an alternative or complementary agent to conventional glaucoma therapies. The purpose of this study is to generate pooled estimates on the IOP-lowering effects of THC. This systematic review and meta-analysis article was registered a priori on PROSPERO (CRD420251007916). MEDLINE, EMBASE, and Web of Science were searched for studies reporting IOP reduction following THC administration. Two reviewers independently performed screening, data extraction, and risk of bias assessments. A random-effects meta-analysis of mean differences was performed to estimate the overall pooled peak percentage reduction in IOP following THC administration, stratified by route of THC administration. Five studies were included, consisting of a total of 99 patients and 69 with THC exposure/intervention. Overall, the pooled peak percentage reduction in IOP after THC administration was 14.66% (95% CI: [3.38%, 25.93%]; p < 0.005). By route of THC delivery, the pooled peak percentage reduction in IOP was 33.27% (95% CI: [20.36%, 46.17%]; p < 0.0001) with the IV route. It was 10.65% (95% CI: [-7.60%, 28.89%]) with the oral route and 9.36% (95% CI: [-8.89%, 27.6%]) with the topical route. Four studies reported the peak percentage reduction in IOP after THC and control administration. From these studies, the pooled peak percentage reduction in IOP after THC was 6.88% (95% CI: [-9.56%, 23.33%]; p = 0.41) and nonsignificantly different from control. Our study generated literature-pooled estimates of the overall and route-stratified peak percentage reduction in IOP following THC administration. THC significantly reduced IOP, although comparatively less significant to the control group.

Paper Type

📄 Research

Publication

Journal: Canadian journal of ophthalmology. Journal canadien d'ophtalmologie
Published: May 1, 2026
PMID: 42069343
DOI: 10.1016/j.jcjo.2026.04.003

Authors (3)

Thanansayan Dhivagaran Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON.
Fahad Butt Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON.
David Mathew Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, ON; Donald K. Johnson Eye Institute, Krembil Research Institute, University Health Network, Toronto, ON. Electronic address: david.mathew@mail.utoronto.ca.