Improved method for calculation of corneal topography for any photokeratoscope geometry.

Accurate and efficient calculation of the anterior corneal surface topography by photokeratoscopy has become important for the management or surgical treatment of refractive errors. Methods have been published that describe such calculations. The algorithms described here eliminate an assumption made in some of the earlier computational methods without an excessive increase in the computation time or increased sensitivity to measurement errors. This results in an enhanced accuracy for reconstructing corneal topographies. Computer simulation results indicate an improved accuracy in measuring the topography for nonspherical corneas. The equations given here apply to any general photokeratoscope geometry and can easily be used in computer programs. In a notable previous publication concerning the more common flat faceplate keratoscope geometry, several of the equations were presented with errors. These errors are identified as an aid to anyone who had already attempted to use those equations in a computer program.