Patent ID: 6471647
Filing Date: 2002-10-29
Classification: A61B

Abstract:
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.