[Mechanical model of ocular pulsatile flow for evaluating the ocular blood flow device with known pressure...

Ocular perfusion consists of steady-state and pulsatile components of flow. The latter can be measured clinically by means of the 'Ocular Blood Flow' (OBF)-device (O.B.F. Ltd, Crowshearst, GB).

1) Mechanical 'eye': To mechanically simulate the effect of pulsatile flow in the eye, a mechanical 'eye' model was built: A brass chamber (9 cm3) 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 changes in pressure within the mechanical chamber. 2) Mechanical 'heart': To mechanically simulate pulsatile flow (i.e. pulsations in pressure like those within the human eye), two reservoirs were constructed of acrylic plastic and mounted on an upright optical bench with a millimeter scale. The reservoirs were constantly filled to overflowing with perfusate (tap water) and were connected by rubber tubing to the 'eye'-chamber. A computer-guided valve alternated between the 'systolic' and 'diastolic' columns of different, independently adjustable elevation. Frequency and duration of each pressure phase could also be independently adjusted via dialog with the computer. Input pressure levels were measured just outside the input using a transducer. The OBF-device measured the chamber pressure at the center of the rubber 'cornea'.

Even the slightest alterations in the parameters (frequency, amplitude, and pressure) were precisely detected by the OBF-device, both graphically and numerically.

Challenged by the mechanical model, the OBF-device demonstrated high sensitivity and fidelity of reproduction of any and all pulsations in intra- "ocular" -pressure.