Using Computer Based Topography Programs For Initial Fit Of RGP Lenses.

Background: Computerized corneal topography manufacturers argue that videokeratoscopy instruments can hypothesize a more accurate initial contact lens fit in comparison to empirical fits because the instrument gives more information about the surface of the cornea. Three rigid gas permeable contact lens' fitting software programs were analyzed in an effort to determine how the initial fit of the lenses designed by the programs compared to those of an empirical lens fit. Methods: A total of 40 eyes were included in the study. Topographies were obtained on both the Humphrey and Medmont topographer, and the Humphrey Masterfit software, Medmont Studio software, and Focal Points software were used to analyze the topographies. Four different contact lenses were order for each eye based on the three topographies and empirical data. The lenses' initial fits were then compared based on vertical centration, horizontal centration, base curve, edge lift, and over-refraction.
Results: Of all initial fits, 25.0% were optimal in all categories analyzed. Refraction showed the most variance between the groups with the Medmont studio and the Humphrey Masterfit proving to be optimal more often than the empirical fit within this category. Conclusions: Based on the results of this study, computerized corneal topographic software programs have shown to have comparable results to empirical fitting method as a starting point for rigid gas permeable fitting.