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S. R. Uhlmann, E. Buehner, U.-C. Pietsch, A. Bringmann, P. Wiedemann, C. Foja; Regulatory Mechanisms of Intraocular Pressure and Aqueous Fluid Dynamics - Analysis in a Pig Model. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3821.
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The aim of this study was to investigate the regulatory mechanisms of intraocular pressure (IOP) in the porcine eye in situ. The influences of two topically acting anti-glaucoma agents and two different anaesthetic techniques were analyzed.
Experiments were conducted in 40 healthy domestic white pigs. The following groups were examined: (A) without any topical medication, either isoflurane inhalation anaesthesia (A1) or total intravenous propofol anaesthesia (A2); (B) beta-adrenoceptor antagonist timolol (isoflurane anaesthesia); (C) prostaglandin analogue bimatoprost (isoflurane anaesthesia). IOP was measured by the Schioetz tonometer (indentation method). To evaluate the aqueous humor production and the outflow facility the oculopression-tonography (OPT) was used. The IOP dependence of the pulsation of the ophthalmic artery was registered by the ocular-oscillo-dynamography (OODG).
A significant decrease in IOP of 13.4 % under intravenous injection of propofol (A2) and of 9.9 % under inhalation of isoflurane (A1) was measured in comparison to baseline IOP before general anaesthesia. During the pressure release in the OODG, the first pulsation of the ophthalmic artery appeared earlier in the isoflurane group than in the propofol group. A single eye drop application of timolol or bimatoprost two hours before the baseline IOP measurement prior to general anaesthesia led to an IOP decrease of 12.7 % and 9.4 %, respectively. OPT demonstrated a significantly increased outflow facility in group C and a decreased aqueous humor production in group B compared to A.
The significant IOP-lowering effect of inhalation and total intravenous anaesthesia has to be considered in animal models. The improvement of the outflow facility by bimatoprost and the reduction of aquous humor production by timolol could be sufficiently demonstrated using the OPT in this pig model.
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