The Effects of a Fixed Combination of 0.5% Timolol and 1% Dorzolamide on Optic Nerve Head Blood Circulation

Abstract

The purpose of the present study is to evaluate the effects of a fixed combination of 0.5% timolol maleate (TM) and 1% dorzolamide hydrochloride (DZ) (FCTD(1%)) on optic nerve head (ONH) blood circulation. A drop of 0.5% TM, 1% DZ, or FCTD(1%) was topically administered to the right eyes of 15 healthy Japanese subjects, and a drop of saline was likewise administrated to their left eyes. Systemic blood pressure, heart rates (HRs), intraocular pressures (IOPs), ocular perfusion pressures, and blood circulation by a laser speckle flowgraphy at the ONH were measured before administration, and again at 1.5 and 6 h afterward. FCTD(1%) caused a significant increase in ONH blood circulation 6 h after the administration, while 0.5% TM and 1% DZ had no significant effect. The IOPs were significantly decreased in 0.5% TM (P<0.01) and FCTD(1%) (P<0.05) when compared with the saline-treated eyes at 1.5 and 6 h after administration, while 1% DZ did not show a statistically significant decrease. There were no significant changes in other systemic parameters except for a significant transient decrease in the HRs observed in 0.5% TM (P<0.01) when compared with the baseline at 1.5 h after the administration. Our current results suggest that FCTD(1%) caused a significant increase in ocular blood circulation on the ONH in healthy Japanese subjects, presumably by a synergistic effect of 0.5% TM and 1% DZ, although neither 0.5% TM nor 1% DZ on their own had a significant effect.