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HA Reitsamer, JW Kiel; A Rabbit Model To Study Orbital Venous Pressure, Intraocular Pressure And Ocular Hemodynamics Simultaneously . Invest. Ophthalmol. Vis. Sci. 2002;43(13):839.
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Purpose: To measure orbital venous pressure (OVP) and determine the effects of changes in mean arterial pressure (MAP) on OVP, intraocular pressure (IOP), episcleral venous pressure (EVP) and ciliary and choroidal blood flows. Methods: The experiments were performed in anesthetized rabbits. In all animals, MAP, IOP and 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 in one group, and ciliary blood flow in a second group. A servonull micropressure system was used to measure EVP in a third group. The protocol for all 3 groups entailed varying MAP mechanically with occluders on the abdominal aorta and the vena cava inferior. View OriginalDownload SlideView OriginalDownload Slide Results: The OVP and IOP relationship was linearly correlated (r = 0.996) during mechanical manipulation of MAP. EVP also correlated well with OVP and IOP (r ≷ 0.8). Resistance calculations based on choroidal and ciliary blood flows and the pressure gradients indicate active adjustment of arterial resistance and passive changes of venous resistance in response to changing MAP. Conclusion: The rabbit orbital venous sinus permits continuous measurements of OVP. The present findings show the importance of OVP in IOP homeostasis and its involvement in ocular hemodynamics.
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