US 6,471,647 B2Granted

Method of operating tonometer

AssigneeFFHK Development Company LLC

InventorsFrancis Y. Falck, Robert W. Falck

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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.

Claims22

Dependent claims

A method of automatically ensuring concentric engagement of a cornea or an eye with an applanation surface of a tonometer prism before proceeding with an intraocular pressure measurement, the method comprising:

a. illuminating the applanation surface with radiation incident on an internal face of the applanation surface and reflected from the internal face of the applanation surface to a detector in a spacial distribution of light intensity that varies radially from a center of the applanation surface to a periphery of the applanation surface;
b. directing to a microprocessor a signal from the detector representing total light reflected from the applanation surface and received by the detector;
c. programming the microprocessor to determine that the signal from the detector at a predetermined non-contact value represents the radially varied light intensity reflecting from the applanation surface to the detector when the applanation surface is not in contact with the eye being examined;
d. programming the microprocessor to determined that the signal from the detector at a predetermined concentric contact value less than the non-contact value represents the radially varied light intensity reflecting from the applanation surface to the detector when the applanation surface concentrically contacts the cornea of the eye being examined;
e. programming the microprocessor to determine that the signal from the detector at an eccentric contact value less than the non-contact value and differing from the concentric contact value represents the radially varied light intensity reflecting from the applanation surface to the detector when the applanation surface eccentrically contacts the cornea of the eye being examined;
and
f. programming the microprocessor to proceed with a measurement of intraocular pressure of the eye only upon determination by the microprocessor that the signal having the concentric contact value has been received from the detector.

4 more elements

A method of automatically operating a tonometer to distinguish between concentric contact of a tonometer prism with a cornea of an eye and eccentric contact of the tonometer prism with a cornea of an eye, the method illuminating an interior of the prism with light transmitted from an emitter to an applanation surface and from the applanation surface to a detector, a signal from the detector responsive to the total light received by the detector being transmitted to a programmed microprocessor and the method comprising:

a. configuring the illumination reflected from the applanation surface to vary in a spacial distribution of intensity radially from a center of the applanation surface to a periphery of the applanation surface so that the signal from the detector to the microprocessor representing an amount of light reaching the detector upon concentric contact of the applanation surface with a cornea differs distinguishably from the signal from the detector to the microprocessor representing an amount of light reaching the detector upon eccentric contact of the applanation surface with a cornea;
and
b. programming the microprocessor to proceed automatically with an intraocular pressure measurement only upon receiving the signal representing concentric contact of the applanation surface with a cornea.

A method of operating an applanation tonometer having a microprocessor and a replaceable prism with an applanation surface, the method comprising:

a. signaling the microprocessor when a previously unused prism is placed in the tonometer for use in measuring an intraocular pressure of an eye;
b. programming the microprocessor to perform a predetermined limited number of eye examinations with the previously unused prism;
c. programming the microprocessor to disable the tonometer from performing any intraocular pressure measurements after the predetermined limited number of intraocular pressure measurements has been fulfilled;
d. removing a prism used in making the predetermined limited number of intraocular pressure measurements;
e. replacing the removed prism with a previously unused prism;
and
signaling the microprocessor that a previously unsued prism has been mounted in the tonometer to enable the microprocessor to proceed with the predetermined limited number of intraocular pressure measurements.

4 more elements

Dependencies are inferred from the claim text.