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M. Shahidullah, C.S. Law, M.K. Yap, C.–H.H. To; Relationship Between Ciliary Body Perfusion Rate and Aqueous Humour Inflow . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2412.
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Purpose: Simultaneous measurement of ciliary blood flow, intraocular pressure, aqueous humour flow and arterial pressure in order to determine their relationship in an isolated whole eye preparation. Methods: Pig eyes collected from the abattoir were cannulated through the ophthalmic artery and perfused with oxygenated Krebs’ solution at 37 °C. Arterial flow rate was varied adjusting the rpm of the peristaltic pump used. Aqueous humour formation was estimated by the "fluorescein dilution technique". Intraocular pressure was measured by direct cannulation of the anterior chamber and vascular pressure was recorded using digital pressure transducer. Results: Arterial perfusion pressure and intraocular pressure were significantly changed due to changes in arterial flow rate. Aqueous humour flow rate remained unchanged until the flow rate was lowered to 25% of the control, when it was decreased by 40%. The arterial perfusion pressures were changed from a control value of 83.9±2.2 mmHg (n=7) to 56.6±1.0 mmHg (P<0.001; n=7); 60.8±0.7 mmHg (P<0.001; n=7) and 74±0.7 mmHg (P<0.001, n=7) in response to arterial flow rates of 2 ml/min (control), 0.75 ml/min, 1.5 ml/min and 3.0 ml/min, respectively. Similarly, the intraocular pressure were changed significantly from 13.4±0.2 mmHg (control; n=7) to 10.5±0.2 mmHg (P>0.001; n=7), 11.7±0.24 mmHg (P<0.001; n=7) and 14.5±0.2 mmHg (P<0.01; n=7) at flow rates of 2 ml/min, 0.75 ml/min, 1.5 ml/min and 3.0 ml/min respectively. Conclusions: Although both intraocular and arterial pressures change with the arterial flow rates, aqueous humour inflow is independent of arterial/ciliary perfusion rate until it is reduced to 25% of control. Therefore it indicates that aqueous humour inflow remains constant in in vivo situation where arterial pressure is maintained adequately.
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