Does cannabis lower intraocular pressure in glaucoma?

Cannabis does lower intraocular pressure (IOP) — this is well-established. THC reduces IOP by 25–30% for 3–4 hours after smoking, comparable to some pharmaceutical agents. The mechanism involves CB1 receptors in the ciliary body reducing aqueous humor production, and vasodilation of ocular blood vessels. However, the American Academy of Ophthalmology does not recommend cannabis for glaucoma for several reasons: (1) Duration is too short — glaucoma requires 24-hour IOP control; cannabis would require dosing every 3–4 hours, including overnight. (2) Systemic side effects (cognitive impairment, cardiovascular effects) at the required frequency are unacceptable for a chronic condition. (3) Hypotension from cannabis may reduce ocular perfusion pressure, potentially worsening optic nerve damage despite lower IOP. (4) Tolerance develops rapidly. Topical cannabinoid formulations that avoid systemic effects are under investigation.