Abstract: A keratometer includes illuminating optics centered along a common measurement axis in alignment with a patient's cornea and with area detection means of the keratometer. A conical reflector is positioned with its apex facing a source of collimated light, such that light incident upon the conical reflector is divided into rays expanding radially outward from the measurement axis. A frusto-conical reflector surrounds the conical reflector to receive the radially expanding rays and redirect them along the measurement axis as an annulus of light large enough to pass around the area detector to a mire ring occluder and refractor which pass a refined converging annulus of light to the cornea.

Abstract: The disclosure relates to a joystick for positioning a test axis of an ophthalmic instrument relative to an eye of a patient. In a preferred embodiment, the joystick includes an actuator extending therefrom and arranged to alternately engage a pair of motor control switches incident to slight rotation of the joystick in opposite directions, thereby activating a motor drive to raise and lower the test axis.

Abstract: Apparatus and method for accurately quantifying the instantaneous radius curvature of a large plurality of points on the corneal surface is disclosed. A video image of the corneal surface accurately positioned at a predetermined point on the optic axis of measurement is obtained. The predetermined point is defined by intersecting low power laser beams. The video image is radially scanned from an original position at point defined by the intersection of the visual axis with corneal surface. Accurate measurements of the two-dimensional image radii of a plurality of illuminated mires reflective upon the corneal surface are made and corrected for camera distortions, quantization error and the different magnification occurring for different size corneas. The instrumentation is calibrated by using a plurality of mirror-like spheres of precisely known spherical radii.