Intravenous epinephrine stimulates aqueous formation in the human eye

An experiment was done to determine if intravenously administered epinephrine would stimulate the rate of aqueous humor flow in sleeping human subjects. Twenty normal volunteers participated in a double-masked randomized placebo-controlled study. The rate of aqueous humor flow was measured by the rate of clearance of topically applied fluorescein. Measurements were made on two separate nights while the subjects slept, once during a placebo infusion and again during an intravenous infusion of epinephrine (rate, 1 microgram/hr; a rate calculated to be threefold the basal adrenal secretion in supine sedentary human subjects). Compared with placebo, epinephrine infusion had no effect on the blood pressure of sleeping subjects, increased the heart rate by 10%, and increased aqueous flow by 27%. Systolic blood pressure was 112 +/- 9 mmHg (mean +/- standard deviation) during placebo infusion and 114 +/- 13 during epinephrine infusion. The heart rate was 60 +/- 10 beats/min during placebo and 67 +/- 14 during epinephrine infusion (P = 0.011). Aqueous flow was 1.11 +/- 0.51 microliters/min during placebo and 1.42 +/- 0.52 during epinephrine infusion (P = 0.016). It was concluded that adrenal medullary secretion can stimulate aqueous formation and may explain in part the circadian rhythm of aqueous flow.