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Nikolaos Karyotakis, Harilaos S. Ginis, Anna I. Dastiridou, Miltiadis K. Tsilimbaris, Ioannis G. Pallikaris; Manometric Investigation Of The Relationship Between Pulsatile Ocular Blood Flow And Intraocular Pressure In Living Human Eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6862.
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The hemodynamic impact of elevated intraocular pressure has been implicated in ischemic or hypoxic models of ocular disease. The purpose of this study was to employ a manometric method that involves cannulation of the anterior chamber to investigate the relationship between intraocular pressure (IOP), ocular pulse amplitude (OPA) and pulsatile ocular blood flow (POBF).
Nine patients (3 men and 6 women, aged 64 years, sd 14) were measured during cataract surgery. The study was approved by the Institutional Review Board. The anterior chamber of each eye was cannulated and connected to a device featuring a pressure sensor and a dosimetric pump. The transducer output can be continuously recorded while the dosimetric pump can be used to control IOP. The anterior chamber of each eye was infused in steps of known volume of saline until the IOP was increased to 40 mmHg. At 40 mmHg the infusion stopped and the sensor recorded the IOP decay curve over time for 3 minutes. The POBF was estimated based on the ocular volume and pressure changes. A purposely developed Matlab (The Mathworks, Inc, MA, USA) script was applied in order to identify, filter and average series of ocular pulses. The POBF was estimated in range of pressures from 40 mmHg to 20 mmHg depending on the IOP decay curve over time of each subject. Ocular rigidity of each eye was calculated during the infusion process and the rigidity coefficient was used to convert the measured pressure changes to corresponding volume changes.
The average POBF at maximum IOP 40 mmHg was 707.5 (sd 249.1) μL/min, and the POBF at minimum IOPs was 1019.5 (sd 297) μL/min. The POBF was increasing inversely with IOP for all subjects, with mean difference between the maximum and minimum values at 304.5 (sd 102.8) μL/min.
The POBF is decreased at elevated IOP levels suggesting that the pulsatile component of blood flow is determined by the value of IOP. Also other parameters like ocular rigidity systemic and baseline IOP are correlated to POBF.
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