Effects of topical carteolol and timolol on tissue circulation in the iris and choroid.

PURPOSE

To evaluate the effects of topical carteolol or timolol on tissue circulation in the iris and posterior choroid.

METHODS

After a topical instillation of 20 microl of 2% carteolol, 0.5% timolol, or physiological saline (for control) into one eye, and physiological saline into the other eye of pentobarbital-anesthetized Dutch pigmented rabbits, normalized blur value; a quantitative index of tissue blood velocity in the iris (NB(iris)) and posterior choroid (NB(cho)) was obtained using the laser-speckle method. Intraocular pressure (IOP), blood pressure and pulse rate were serially monitored for 2 hours after instillation. Using separate groups of rabbits, NB(iris) and IOP were measured before and after 20-day twice-daily unilateral treatment of carteolol or timolol.

RESULTS

After a single instillation of carteolol, NB(iris) was significantly greater only in the treated eyes than control eyes (P = 0.0050, repeated measures two-way ANOVA), while NB(cho) showed no significant change. IOP in the treated eyes significantly reduced (P = 0.0005). Bilateral reductions of tissue vascular resistance in the iris were found after carteolol instillation (P = 0.0183 approximately 0.0322). After timolol instillation, serial changes in NB(iris) and NB(cho) in the treated eyes were significantly different from those in control eyes (P = 0.0129, 0.0031), while there were no significant differences at any of time points (Mann-Whitney test); IOP in both eyes was significantly reduced (P = 0.0096 approximately 0.0005); tissue vascular resistance in the iris and posterior choroid showed no significant changes. After 20-day treatment, NB(iris) in the both eyes of carteolol-treated rabbits significantly increased from the baseline (P = 0.0280, 0.0425, Wilcoxon signed rank test) and NB(iris) in timolol-treated eyes significantly decreased (P = 0.0280).

CONCLUSIONS

A single instillation of topical carteolol significantly increased the iris tissue blood velocity in the treated eye and reduced the tissue vascular resistance in both eyes. Topical timolol tended to decrease tissue blood velocity in the iris and choroid of the treated eye, but showed no significant effects on tissue vascular resistance in the both tissues.