Purpose:
To investigate the effect of topical travoprost on ciliary blood flow regulation in rabbits.
Methods:
Mean arterial pressure (MAP), intraocular pressure (IOP) and orbital venous pressure (OVP) were measured by direct cannulation of the central ear artery, the vitreous, and the orbital venous sinus, respectively. Doppler flowmetry was used to measure ciliary blood flow (CilBF, n=6) while MAP was manipulated mechanically with occluders around the aorta and vena cava, thus changing ocular perfusion pressure (PP) over a wide range. Pressure–flow (PF) relationships were performed at control and in response to a single drop of topical travoprost (0.004%). As a control perturbation in the same experiment, brimonidine (0.15%) was applied to the cornea after CilBF has reached a plateau in response to topical application of travoprost (15 minutes after application).
Results:
Travoprost significantly increased ciliary blood flow by decreasing ciliary vascular resistance (CilR) (–10%). MAP, IOP, PP and HR did not change compared to baseline. Subsequent topical application of brimonidine lowered CilBF by increasing CilR by 170% and also lowered IOP, OVP and HR. Ciliary pressure flow relationships were shifted upwards by travoprost and shifted downwards by brimonidine. The results and percent changes from baseline are summarized in the table. Baseline effects of topical Travoprost (0.004%) and Brimonidine (0.15%)
Conclusions:
Travoprost is a mild short term vasodilator in the ciliary vascular bed whereas control application of brimonidine confirmed previously reported vasoconstrictor activity of the drug in the ciliary circulation.
Keywords: ciliary body • blood supply