Miniature Passive Pressure Transensor for Implanting in the Eye

A newly developed method for measurement of intraocular and other physiological pressures consists of a novel displacement transducer contained in a distensible pillbox small enough (3 to 60 ¿l) to be implanted in the eye of a small laboratory animal. Nothing pierces or even touches the globe. This passive resonant transensor absorbs energy from an oscillating detector coil outside of the animal at a frequency dependent upon the pressure in the eye. Passive operation provides extended life, but limits useful range to less than 10 transducer diameters, which has proved sufficient for intraocular pressure measurement.