Patent ID: 6179779
Filing Date: 2001-01-30
Classification: A61B

Abstract:
In a tonometer having an applanation prism with an applanation surface that engages a cornea of an eye being examined, an optical system including an emitter directing light into the prism to be incident on and at least partially reflected from the applanation surface and a detector detecting light reflected from the applanation surface and a microprocessor responsive to a signal from the detector representing total light reflected from the applanation surface and received by the detector, the improvement comprising:a. the emitter, detector, and prism being arranged relative to each other so that spacial distribution of light intensity reflected from the applanation surface varies radially from a center of the applanation surface to a periphery of the applanation surface;b. the microprocessor being programmed 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;c. the microprocessor being programmed to determine 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; andd. the microprocessor being programmed to determine that the signal from the detector at an eccentric contact value less than but 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.