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

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