Caffeine has no clinically significant effect on aqueous humor flow in the normal human eye

The effect of orally administered caffeine (400 mg) on aqueous humor flow was studied in 20 normal human subjects. The rate of aqueous flow was measured by fluorophotometry. There was no statistically significant difference in aqueous flow measured hourly from 1 to 4 hours after the administration of caffeine. There also was no statistically significant difference in intraocular pressure (IOP) measured 4 hours after caffeine ingestion. The sample size was large enough to have detected a 15% change in flow, had it occurred.