Effect of topical adrenergic agents on tissue circulation in human optic nerve head evaluated with a laser speckle microcirculation analyser

The effects of a single instillation of 2% carteolol or 0.1% dipivefrine on the tissue circulation in the human optic nerve head (ONH) was studied using a laser speckle tissue circulation analyser in 12 healthy volunteers. In the first experiment, normalized blur (NB), a quantitative index of peripheral blood velocity, was measured every 0.125 sec in an area located in the temporal site of ONH free of visible surface vessels and averaged over 5 pulses (mean NB) in both eyes before, 1.5, 3, and 4.5 hours after a 30 microliters instillation of placebo to serve as a control. Intraocular pressure (IOP), blood pressure (BP), and pulse rate (PR) were also measured. In the second experiment, a 30 microliters drop of 2% carteolol (n = 6) or 0.1% dipivefrine (n = 7) was instilled in one randomly chosen eye and the placebo for each drug in the other eye, and the above parameters were measured according to the same time schedule as in the first experiment in a double masked manner. After topical carteolol, carteolol concentration in the plasma (CC) was also measured. In the control experiments, none of the parameters showed any significant change. After topical carteolol, the IOP was significantly lower between 1.5 and 4.5 hrs in the carteolol-treated eyes and at 1.5 and 4.5 hrs in the fellow eyes as compared with that obtained in the control experiment. The mean NB was significantly higher at 3 hrs (23.1%) in carteolol-treated eyes, and at 3 hrs (17.2%) in the fellow eyes, as compared with that obtained in the control experiment (p < 0.05). BP and PR showed little change. The maximum CC at 3 hrs averaged 522 pg/ml. Thus a single instillation of carteolol may increase the tissue blood velocity in ONH in the human eye. After topical dipivefrine, the IOP was significantly lower at 4.5 hr in the dipivefrine-treated eyes than that obtained in the control experiment (p < 0.05). Mean NB, BP and PR showed no significant change.