Short answer
There is no established THC dose for glaucoma relief. Research used smoked cannabis at 1 to 2 percent THC by weight. Those doses cut intraocular pressure (IOP) for about 2 to 4 hours. Glaucoma care needs pressure control across all 24 hours. That gap is the main problem.
glaucoma cannabis drops legal states
What the studies measured
Hepler and Frank reported in 1971 that smoked cannabis lowered IOP in healthy volunteers by about 25 percent. The peak came 60 to 90 minutes after smoking. Pressure returned to baseline by hour 3 or 4.
Dose ranges in the literature run from about 5 mg to 20 mg THC by mouth, or a few puffs of flower. No dose in those studies matched the duration or the steadiness of prescription drops.
cannabis and eye pressure research studies
Comparison with standard drops
- Latanoprost: cuts IOP 25 to 33 percent. One dose each night.
- Timolol: cuts IOP 20 to 25 percent. Two doses each day.
- Smoked cannabis: cuts IOP about 25 percent. Effect ends in 2 to 4 hours. That means 6 to 12 sessions a day to hold pressure down.
Side effects at repeated doses
Six to 12 doses a day means constant psychoactivity. Recorded effects include fast heart rate, blood pressure drops on standing, sedation, short-term memory loss, and poor coordination. Older adults with glaucoma face fall risk. The American Academy of Ophthalmology does not recommend cannabis or THC for glaucoma.
cannabis and eye pressure research studies
Where convenience fits
Patients ask about cannabis because drops demand a routine, refills, and cost. The data point the other way. One drop at night holds pressure for 24 hours. Cannabis holds it for 2 to 4 hours. Convenience favors the drop.
Questions to bring to an eye doctor
Ask about IOP readings before and after any cannabis use, the route (smoked, oral, sublingual), the dose in milligrams, and how long the effect lasted. Keep a log. Do not stop a prescribed drop on your own.