Abstract: An applanation tonometer uses an active pixel sensor array to accurately detect total illumination in a region surrounding an applanated area so that a microprocessor can determine the applanated area based on an inversion of the illumination received by the sensor.

Abstract: A microprocessor-controlled tonometer measures both systole and diastole occurring in intraocular pressure so that this information can be used to estimate perfusion pressure. The microprocessor determines a ratio between ocular pulse amplitude and mean intraocular pressure, derives a multiplier from the ratio, multiplies the mean intraocular pressure by the multiplier to estimate mean central retinal artery pressure, and then estimates perfusion pressure by subtracting mean intraocular pressure from the estimate of central retinal artery pressure.

Abstract: A tonometer uses ambient light available in an eye examining room, rather than a dedicated source of light, to examine a characteristic of an eye. A digital camera in the tonometer views an image of the eye as it is engaged by a contactor that applanates or indents the cornea. An electromagnetic mount for the contactor can supply a force pressing the contactor against the eye. While the examiner observes the resulting image a strain gauge can also measure the deformation pressure applied to the eye by the contactor. A microprocessor can then determine a characteristic of the eye from signals supplied by the camera and the strain gauge or the electromagnet force applier.

Abstract: An applanation tonometer and its operation involve an actuator pressing a prism with a variable and determinable force against a cornea of an eye while a source directs light to reflect from an applanation surface of the prism to a detector producing a detected light signal received by a microprocessor. Such a tonometer produces a diastolic phase signal and a systolic phase signal representing the complete intra ocular pressure experience of the eye being examined. The signal information allows combined diastolic and systolic IOP to be determined in several corroborating ways and also yields measures of ocular blood flow and tonography.

Abstract: A replaceable applanation prism for an eye examining instrument is made to be discarded after each use. A bendable tab molded on the prism is deformed by a strain gauge as the prism is inserted into a prism holder, and a signal from the strain gauge is used to verify that a previously unused prism has been inserted into the holder. A microprocessor is programmed to recognize the signal produced by initial deformation of the prism tab so as to proceed with an eye examination only after receiving the strain gauge signal verifying that a previously unused prism has been inserted.

Abstract: A replaceable applanation prism for an eye examining instrument is made to be discarded after each use. A bendable tab molded on the prism is deformed by a strain gauge as the prism is inserted into a prism holder, and a signal from the strain gauge is used to verify that a previously unused prism has been inserted into the holder. A microprocessor is programmed to recognize the signal produced by initial deformation of the prism tab so as to proceed with an eye examination only after receiving the strain gauge signal verifying that a previously unused prism has been inserted.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45° to the longitudinal axis. Light from an emitter confronting one of the ports is incident on the applanation surface at about 45° so that light reflecting internally of the prism from the applanation surface is directed toward the opposite port for detection. The portion of the light internally reflected from the applanation surface provides a signal indicating the size of the applanated area, from which intraocular pressure is determined.

Abstract: An applanation tonometer and its operation involve an actuator pressing a prism with a variable and determinable force against a cornea of an eye while a source directs light to reflect from an applanation surface of the prism to a detector producing a detected light signal received by a microprocessor. Such a tonometer produces a diastolic phase signal and a systolic phase signal representing the complete intra ocular pressure experience of the eye being examined. The signal information allows combined diastolic and systolic IOP to be determined in several corroborating ways and also yields measures of ocular blood flow and tonography.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45° to the longitudinal axis. Light from an emitter then passes through the emitter port and crosses the prism axis to be incident and reflected from an emitter-reflecting surface of the prism and become incident on the applanation surface. Light reflected from the applanation surface is incident on and reflected from a detector-reflecting surface opposite and parallel with the emitter-reflecting surface to proceed across the prism axis to the detector port. Such an arrangement produces reliable applanation signals and varies the spacial intensity of light reflected from the applanation surface so that the tonometer can automatically distinguish between concentric and eccentric contact of the applanation surface with a cornea.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45° to the longitudinal axis. Light from an emitter confronting one of the ports is incident on the applanation surface at about 45° so that light reflecting internally of the prism from the applanation surface is directed toward the opposite port for detection. The portion of the light internally reflected from the applanation surface provides a signal indicating the size of the applanated area, from which intraocular pressure is determined.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45° to the longitudinal axis. Light from an emitter then passes through the emitter port and crosses the prism axis to be incident and reflected from an emitter-reflecting surface of the prism and become incident on the applanation surface. Light reflected from the applanation surface is incident on and reflected from a detector-reflecting surface opposite and parallel with the emitter-reflecting surface to proceed across the prism axis to the detector port. Such an arrangement produces reliable applanation signals and varies the spacial intensity of light reflected from the applanation surface so that the tonometer can automatically distinguish between concentric and eccentric contact of the applanation surface with a cornea.

Abstract: An applanation tonometer with a replaceable prism for contacting a cornea has emitter and detector ports arranged opposite each other on opposite sides of a longitudinal axis, with the ports aimed at about 45 ° to the longitudinal axis. Light from an emitter then passes through the emitter port and crosses the prism axis to be incident and reflected from an emitter-reflecting surface of the prism and become incident on the applanation surface. Light reflected from the applanation surface is incident on and reflected from a detector-reflecting surface opposite and parallel with the emitter-reflecting surface to proceed across the prism axis to the detector port. Such an arrangement produces reliable applanation signals and varies the spacial intensity of light reflected from the applanation surface so that the tonometer can automatically distinguish between concentric and eccentric contact of the applanation surface with a cornea.

Abstract: A tonometer divides internally incident light at the applanating surface of a prism so that light incident in the applanation area is refracted into the eye and light incident around the applanation area is internally reflected within the prism. Infrared light is preferred for this, and the amount of the reflected light is detected to provide an objective indication of the size of the area that is applanated. This allows intraocular pressure to be determined objectively from the force difference applied to the prism to change the applanation area between reference and measurement sizes, both of which are reliably determined from previous calibration for the amount of the reflected light. Many variations are possible in applying a variable force to the applanating prism and on operating the instrument with the preferred microprocessor, which can also store, display, and manipulate relevant patient data.