Effect of topical timolol on optic nerve head circulation in the cynomolgus monkey.

Objective: To evaluate the effect of topical timolol on the optic nerve head (ONH) circulation in the cynomolgus monkey.

Methods: Eight cynomolgus monkeys were used. Timolol (0.5%, 30 microL) was instilled twice daily into 1 eye and physiological saline into the other eye for 7 consecutive days. The ONH tissue blood velocity (NB(ONH)) was determined using the laser speckle method. The determinations of NB(ONH) were carried out before the first instillation and 4 hours after the first, the seventh and the last instillation. The IOP was measured periodically. All measurements were performed in a masked manner.

Results: Twice daily 7-day instillation of 0.5% timolol showed no significant effect on the NB(ONH) in either eye, while the IOP was significantly decreased in both eyes.

Conclusions: In the cynomolgus monkey, the ONH circulation was not affected by 7-day twice daily topical timolol treatment.