Effect of chronic epinephrine on aqueous humor flow during the day and during sleep in normal healthy subjects.

Epinephrine 2% drops were administered to one eye and a placebo to the fellow eye twice a day for 2 weeks in 18 normal human volunteers. The circadian rhythm of aqueous humor flow was measured by fluorophotometry. Epinephrine (compared with placebo) had no measurable effect on the rate of aqueous flow or the circadian rhythm of aqueous humor flow. These results suggest either that topical application of epinephrine cannot achieve a sustained effect on the mechanism of aqueous formation compared with endogenous epinephrine or that circulating epinephrine is not the sole or principal hormonal messenger that mediates the circadian rhythm of aqueous flow in humans. An experiment in which epinephrine was administered systemically might clarify this ambiguity.