Mechanical ocular pulsatile-flow model to challenge the 'Ocular Blood Flow' (OBF)-device with known pulsatile-flow values

Background Ocular perfusion consists of steady-state and pulsatile componen ts of flow. The latter can be measured clinically by means of the 'Ocular B lood Flow' (OBF)-device (O.B.F. Ltd, Crowshearst, GB). Methods 1) Mechanical 'eye': To mechanically simulate the effect of pulsati le flow in the eye, a mechanical 'eye' model was built: A brass chamber (9 cm(3)) was machined and fitted with in- and outflow connections. The front opening was covered with a taughtly fixed rubber membrane (COSANO, no. 5203 .106, Migros AG, Zurich) which, as mechanical 'cornea', pulsated with chang es in pressure within the mechanical chamber. 2) Mechanical 'heart': To mec hanically simulate pulsatile flow (i.e. pulsations in pressure like those w ithin the human eye), two reservoirs were constructed of acrylic plastic an d mounted on an upright optical bench with a millimeter scale. The reservoi rs were constantly filled to overflowing with perfusate (tap water) and wer e connected by rubber tubing to the 'eye'-chamber. A computer-guided valve alternated between the 'systolic' and 'diastolic' columns of different, ind ependently adjustable elevation. Frequency and duration of each pressure ph ase could also be independently adjusted via dialog with the computer. Inpu t pressure levels were measured just outside the input using a transducer. The OBF-device measured the chamber pressure at the center of the rubber 'c ornea'. Results Even the slightest alterations in the parameters (frequency, amplit ude, and pressure) were precisely detected by the OBF-device, both graphica lly and numerically. Conclusions Challenged by the mechanical model, the OBF-device demonstrated high sensitivity and fidelity of reproduction of any and all pulsations in intra-"ocular"-pressure.