Purpose:
To compare the effects of different drugs on the orbital venous pressure in anesthetized 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. Laser Doppler flowmetry was used to measure choroidal blood flow invasively through the pars plana. Measurements were made continuously at baseline and after drug application.
Results:
Vasopressin has a dose dependend reducing effect on the orbital venous pressure and also the beta1 receptor antagonists Metoprolol and Nebivolol are able to reduce the orbital venous pressure. However, adenosine has an ambiguous effect, the low dose intravenous infusion (5mg/kg/h) has an increasing effect on the orbital venous pressure whereas the high dose application (10, 20, 30 mg/kg/h) decreases the orbital venous pressure.
Conclusions:
The orbital venous sinus is supplied by the big veins of the head, however, a certain portion of the blood comes from the eye and orbital venous pressure depends on ocular blood flow to a certain extent. If changes of orbital venous pressure are cause by local or systemic changes of hemodanymic parameters or both remains to be investigated.
Keywords: blood supply • drug toxicity/drug effects • intraocular pressure