The Accuracy of Tower' Maps to Display Curvature Data in Corneal Topography Systems

Results. For the spherical surface, both curvature-based paraxial power approximations were uniform over the entire surface because curvature is constant. However, the corneal refractive power increased from center to periphery, demonstrating the known phenomenon of spherical aberration. For the ellipsoids, which have been shown to model the human cornea, curvature-based power approximations decreased from center to periphery because the curvature flattens peripherally. However, refractive power increased from center to periphery. The limits of the central paraxial region for these surfaces was shown to be approximately 2 mm in diameter for the paraxial power approximation used by videokeratographic devices to measure 8 mm in diameter.