Abstract: A tonometer for measuring the intra-ocular pressure of an eye in which a pulse of fluid is projected towards the cornea of the eye to distort the corneal surface by the pressure of the pulse, the distortion in the corneal surface being detected by a change in the reflection of light directed onto the cornea. A constant volume chamber forms part of the fluid delivery system, with an inlet by which fluid under pressure can be supplied to the chamber when a fluid pulse is required. A lens assembly is fixed in the chamber wall for directing light toward an eye under test and a tube extends coaxially through the lens assembly to protrude internally into the chamber, where it is closed off at the end but includes a plurality of apertures in the internally protruding wall section to permit the controlled passage of fluid from the chamber into the tube.

Abstract: A tonometer is described for measuring the intra-ocular pressure of an eye in which a pulse of fluid is projected towards the cornea of the eye to distort the corneal surface by the pressure of the pulse, the distortion in the corneal surface being detected by a change in the reflection of light directed onto the cornea. A fluid delivery system (36, 44, 48) leads to an outlet through which the fluid pulse is applied to the cornea, and a branch (54) leads to a pressure measuring chamber (52), containing a transducer (170) which produces an electrical signal whose value depends on the pressure in the branch. A flow restrictor is removably fitted in the branch (54) and signal processing means (176, 178, 180) (the gain and rise time of which are adjustable by (182) or (186)), is supplied with the output from the transducer. Adjustment of 182, and 186 enable the electrical signal output of the processing means to be adjusted, for calibration.