Radio telemetry of intraocular pressure in vitro

A guard ring pressure transensor, using the principles of surface applanation, was used to transmit intraocular pressure (IOP) from a cadaver canine eye. The transensor consisted of a passive resonant coil/capacitor combination, made pressure sensitive by the movement of a small ferrite plate which acted as its applanating surface. Oscillation induced in the transensor by a remote grid dip oscillator (GDO) was monitored by a digital frequency counter (DFC). The resonant frequency of oscillation in the transensor bore a linear relationship to the in vitro IOP in three separate experiments (coefficient of determination for linear regression, r2 equals 0.90). These data indicate that radio telemetry is feasible, using a miniature applanating passive radio telemetric device for continual monitoring of IOP.