Tonometer

Claim 1

A DEVICE FOR MEASURING THE INTRAOCULAR PRESSURE OF AN EYEBALL COMPRISING: A PROBE HAVING A WALL FOR ENGAGING THE SURFACE OF SAID EYEBALL, A CHAMBER WITHIN SAID PROBE, AN AXIALY MOVABLE PLUNGER CARRIED WITHIN SAID CHAMBER AND HAVING ONE END EXTENDING THROUGH AN APERTURE IN SAID WALL TO THE EXTERIOR, SAID PLUNGER BEING MOVABLE BETWEEN PROTRUDENT AND RETRACTED POSITIONS A SOURCE OF AIR UNDER PRESSURE AT A LOW SUPPLY RATE, A FLUID CONDUIT MEANS COUPLING SAID SOURCE WITH THE INTERIOR OF SAID CHAMBER FOR INTRODUCING SAID AIR INTO SAID CHAMBER FOR ACTING AGAINST SAID PLUNGER TO URGE SAID PLUNGER INTO SAID PROTRUDENT POSITION WITH SAID ONE END PROTRUDING EXTERNALLY FROM SAID WALL WHEN THE PROBE IS OUT OF CONTACT WITH SAID EYEBALL, AT LEAST ONE PORT IN A WALL OF SAID CHAMBER OTHER THAN SAID FIRST MENTIONED WALL FOR VENTING SAID CHAMBER WHEN SAID PLUNGER IS IN SAID PROTRUDENT POSITION FOR MAINTAINING THE PRESSURE OF SAID AIR, AT LEAST WITHIN SAID CHAMBER, AT A LEVEL INADEQUATE TO PREVENT DEPRESSION OF SAID PLUNGER INTO SAID RESTRICTED POSITION WHEN THE WALL OF THE PROBE IS URGED INTO CONTACT WITH SAID EYEBALL, VALVE MEANS CARRIED BY SAID PLUNGER AND OPERABLE UPON SAID DEPRESSION OF SAID PLUNGER TO A PREDETERMINED POSITION FOR ISOLATING SAID PORT FROM SAID FLUID CONDUIT MEANS WHEREBY THE AIR PRESSURE WITHIN SAID CHAMBER AND ACTING UPON SAID PLUNGER IS CAUSED TO RISE CONTINUALLY UNTIL THE RESISTANCE DUE TO SAID INTRAOCCULAR PRESSURE IS OVERCOME AND THE PLUNGER IS AGAIN URGED TOWARD SAID PROTRUDENT POSITION, THE SAID ONE END OF SAID PLUNGER BEING FLUSH WITH THE EXTERIOR SURFACE OF SAID FIRST MENTIONED WALL WHEN SAID PLUNGER OCCUPIES SAID PREDETERMINED POSITION, MEANS FOR LIMITING SAID DEPRESSION OF SAID PLUNGER AT SAID PREDETERMINED POSITION, AND PRESSURE GAUGING MEANS COUPLED TO SAID CONDUIT MEANS ADJACENT SAID CHAMBER FOR INDICATING THE MAGNITUDE OF SAID INTRAOCULAR PRESSURE.