The Ocular Blood Flow Tonograph: A New Instrument for the Measurement of Intraocular Pressure in Rabbits

The Ocular Blood Flow Tonograph (OBFT) and Digilab Pneumatonograph (PTG) were calibrated for use on New Zealand White rabbits using a pressure manometer and performing tonometry at varying known pressures. The calibration experiments showed that a good correlation exists between OBFT measurements and manometric readings of IOP. Moreover, no difference between open and closed stopcock measurements were observed. Corrective equations for conversion of OBFT readings to mm Hg are documented. The OBFT was compared with the PTG and the results showed there was no significant difference between the IOP measured by either instrument in a group of rabbits displaying a range of different IOPs. Regression analysis of the data gave a slope of 0.88 and a correlation co-efficient of 0.78. The OBFT proved easier to use than the PTG under restricted lighting conditions. The OBFT was also used to measure the circadian variation in IOP and to measure the IOP after the topical application of prostaglandin E2and various serotonergic agonists. The combined data demonstrated that the OBFT is an accurate and reliable tonometer for the measurement of IOP in rabbits.