- Design
- Systematic review and random-effects meta-analysis, registered on PROSPERO
- Population
- Five studies, 99 patients, 69 given tetrahydrocannabinol
- Primary outcome
- Peak percentage reduction in intraocular pressure
- Effect
- 14.66% overall (95% CI 3.38% to 25.93%); versus control 6.88% (-9.56% to 23.33%)
A meta-analysis of five studies with 99 patients, 69 of whom received tetrahydrocannabinol, estimated the peak percentage reduction in intraocular pressure after administration. The pooled reduction was 14.66% (95% CI 3.38% to 25.93%).
By route, intravenous administration gave a 33.27% reduction (95% CI 20.36% to 46.17%), while oral (10.65%, -7.60% to 28.89%) and topical (9.36%, -8.89% to 27.6%) did not reach significance. In four studies with a control arm, the pooled reduction with tetrahydrocannabinol was 6.88% (-9.56% to 23.33%), not different from control.
The studies are few and small, and the intravenous route is not a practical treatment. The analysis does not address duration of effect, which has historically been short, or any visual field outcome. It gives no basis for recommending cannabis products for glaucoma.
- Pooled peak intraocular pressure reduction was 14.66% across five small studies.
- Intravenous dosing gave the largest effect; oral and topical were not significant.
- Against control arms the effect was not significantly different.
- No data on duration or visual field outcomes.
- Standard pressure-lowering therapy remains the basis of treatment.
Why it matters
Patients ask about cannabis for glaucoma, and the pooled data do not support it.
Don't overread it
Five small studies with different routes cannot show clinical usefulness or safety.
The statistics, in plain English
A pooled estimate whose interval runs from 3% to 26% is imprecise. When compared with controls, the interval includes zero, which suggests much of the fall could be what the eye pressure does anyway after any intervention.
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