Effect of desmopressin on aqueous humor flow in humans

The rate of aqueous humor flow was studied in 17 human subjects with neurogenic diabetes insipidus. Flow was measured by fluorophotometry on two consecutive afternoons. The first day, subjects used desmopressin to control their diuresis; on the second day, subjects did not use desmopressin and had uncontrolled diuresis. On both days, one eye was treated with the beta-adrenergic antagonist, timolol. With desmopressin, the rate of aqueous humor flow in the untreated eye was 2.53 +/- 0.79 microliters/min (mean +/- standard deviation) and in the timolol-treated eye was 1.69 +/- 0.40 microliters/min. Without desmopressin, the rate of aqueous humor flow in the untreated eye was 2.34 +/- 0.69 microliters/min and in the timolol-treated eye was 1.53 +/- 0.43 microliters/min. Thus, the use of desmopressin was associated with a slightly higher rate of aqueous humor flow in both the normal and the beta-adrenergically inhibited eye (P = .05), and the suppression of aqueous humor flow associated with beta-adrenergic inhibition occurred with and without antidiuretic hormone (P < .001). The observed differences in aqueous humor flow on the two days could have been caused by a direct effect on the eye or to indirect effects, such as the change in plasma osmolality, which changed from 291 +/- 6 mOsm on the desmopressin day to 299 +/- 8 mOsm on the desmopressin-abstention day (P < .001).