ORBSCAN Accuracy in Measuring Corneal Surface Elevation

Abstract : The Surgeon General has recently authorized individuals who have had corneal refractive surgery entry, by waiver, into the services. Since Army aviators already operate under less than optimal visual conditions, the eyes are working at the limits of the visual and optical system. Changes to the optical system must be very accurately assessed to determine impact on vision, and measurement of the cornea is the primary means of verifying the optical characteristics of an eye after refractive surgery. A measurement error of less than +1.0 micrometers is difficult to attain, so an independent assessment of the instrument's accuracy and repeatability is a fundamental prerequisite to corneal topography analysis. This was the research objective in this study. Methods. Two types of corneal topography instruments were used in this study; they included: (1) a videokeratoscope, EyeSys Corneal Analysis System 2000, and (2) a corneal profile topographer, the ORBSCAN, manufactured by ORBTEK. A cornea was measured whose shape closely matched one of the EyeSys calibration objects. Using the living cornea as a calibration surface with known topography, we measured it with the ORBSCAN.