Accuracy and Precision of the Corneal Analysis System and the Topographic Modeling System

Abstract

Two computer-assisted topographic analysis systems were evaluated with calibrated spherical surfaces and normal human corneas. The Topographic Modeling System-1 (TMS-1) was found to be statistically more accurate in determing the power of calibrated spheres near the apex and at 1 mm from the apex than the Corneal Analysis System(CAS).The CAS, however, was statistically more accurate at 3 mm from the apex with each calibrated sphere. The small differences in accuracy between the two instruments, however, are unlikely to be of clinical significance. The topographic patterns on color-coded maps from 22 normal corneas of 11 subjects were similar with the two instruments. Simulated keratometry values with the CAS more accurately identified the keratometerdetermined major cylinder axis compared with the TMS- 1. Conversely, the TMS-1 was more accurate than the CAS at determining the level of corneal astigmatism.