[Combined effect of topical latanoprost and timolol on retinal blood flow and tissue circulation in the optic nerve head in cynomolgus monkeys].

PURPOSE

To evaluate the combined effect of topical latanoprost and timolol on the retinal blood flow and the tissue circulation of the optic nerve head (ONH) in cynomolgus monkeys.

MATERIALS AND METHODS

30 microliters of latanoprost (0.005%) was instilled once daily and timolol (0.5%) twice daily into one eye, and physiological saline as a control into the other eye of 8 cynomolgus monkeys for 6 days. Blood velocity through the retinal veins was measured using a KOWA Laser Speckle Blood Flow Meter. The ONH tissue blood velocity normalized blur (NBONH) was measured using a Laser Speckle Tissue Circulation analyzer. Retinal blood flow, NBONH, intraocular pressure (IOP), blood pressure, and pulse rate were measured before the first instillation, 4 hours after the first instillation on the 2nd experimental day, and 4 hours after the last instillation.

RESULTS

After the first instillation on the 2nd experimental day, the retinal blood flow was decreased to below the baseline, but 6-day instillation caused no significant change from the baseline. Six-day instillation increased the NBONH in the treated eyes by 10% from the baseline and by 7% from that in the fellow control eye. After 6-day instillation, the IOP was lowered by 7.8 +/- 2.7 (mean +/- standard deviation) mmHg and 3.6 +/- 4.3 mmHg in the treated and control eyes, respectively.

CONCLUSION

The results suggest that 6-day instillation of latanoprost once daily and timolol twice daily has no significant effect on the retinal blood flow, and significantly increases the ONH tissue blood velocity in monkey eyes.