Effect of topical carteolol on tissue circulation in rabbit optic nerve head evaluated with the laser speckle microcirculation analyser

The effect of topical 2% carteolol on the tissue circulation in the albino rabbit optic nerve head (ONH) was studied using a laser speckle microcirculation analyser. In the first experiment, normalized blur (NB), the quantitative index of peripheral blood flow rate in the ONH, intraocular pressure (IOP), blood pressure (BP) and pulse rate (PR) were measured under general anesthesia before, and 30, 60, 90, and 120 minutes after a 20 microliters instillation of carteolol in one eye and a placebo in the other eye in a masked randomized manner. In the second experiment, one eye of another group of rabbits received carteolol twice daily for 20 days and the fellow eye a placebo in a randomized masked manner. The NB in the ONH and the IOP were measured before treatment and 2 hours after the last instillation on the 20th day. After a single instillation of carteolol, PR showed a maximum reduction of 14% and the IOP in the carteolol-treated eyes showed a maximum decrease of 22%, while NB in ONH and BP did not show any significant change during the experiment. After 20-day treatment, IOP showed a maximum decrease of 25% in the carteolol-treated eyes and 17% in the placebo-treated eyes. The NB showed a significant increase of 16% (p < 0.01) in the carteolol-treated eyes and 10% (p < 0.05) in the placebo-treated eyes. This indicates that long-term use of topical carteolol increases peripheral blood flow in ONH tissue in the living rabbit eye.