Comparison of simulated K's as measured by computerized videokeratographers to keratometer measurements (English)

AbstractThe accuracy of the simulated K-readings as determined by computerized videokeratographers (CVK) is important with respect to calculating residual astigmatism with rigid contact lens fitting and should correlate well with standard keratometry measurements. In this study, a series of three rigid contact lens buttons with different toricities (1.19, 2.79, and 3.92 D as measured with the keratometer) were measured with a radiuscope and four different CVK systems (three brands). Each button was measured 10 times on each instrument. The results indicated that there were often statistically and clinically significant differences between some of the CVK-determined K-readings as compared to those found with the keratometer. The differences found were in some cases in the order of 25%; for example, in the case of the 3.92 D toric surface, the difference was 0.90 D less cylinder. There were no significant differences between the keratometer measured values and the radiuscope measured values.