Comparison between corneal elevation maps using different reference surfaces with Scheimpflug-Placido topographer.

The purpose of this study was to compare the anterior and posterior elevation measurements using different reference surfaces (spheric, aspheric, and aspherotoric) with Scheimpflug-Placido topography in simple myopic and keratoconus patients. 600 eyes of 600 patients undergoing screening for keratorefractive surgery (500 simple myopic, 100 keratoconus stage 1 and 2) in Sohag refractive center, Egypt, were examined by Scheimpflug-Placido topography (Sirius, CSO, Italy) for both the anterior and posterior corneal elevation maps using the spheric, aspheric, and aspherotoric reference surfaces. 100 keratoconic eyes showed higher discriminating power using the aspherotoric reference surface in both the anterior and posterior elevation maps. The use of aspherotoric reference surface gives more data for eyes with keratoconus and its use is more informative in screening.