Accuracy Of Videokeatographers For Measuring Corneal Toricity.

The use of simulated keratometer readings, as measured by computerized videokeratographers has become an increasingly popular trend in the fitting of contact
lenses. Computerized videokeratographers are able to provide corneal curvature values
(simulated K-readings) that are reported as being equivalent to those found with standard keratometry. Past studies have indicated that there are significant differences between keratometer readings and simulated K-readings. One study, for example, found that there could be as much as a 25% difference between measurements taken by a keratometer and those taken by a computerized videokeratographer. This difference has forced computerized videokeratographer manufactures to create new programs and software in an attempt to make simulated K-readings more equivalent to standard keratometry measurements. The purpose of our study was to determine the accuracy of the new EyeSys Corneal Analysis System (version 3.1) for measuring corneal toricity. The accuracy was determined by making a comparison between measurements taken from a Baush and Lomb keratometer to those taken by the EyeSys. The results of this study revealed that on average, the EyeSys topographer measured .23 D (15%) less corneal toricity than the keratometer. The data for this study was obtained from measurements of 16 eyes, each of which contained at least 1.00 D of corneal toricity (measured by a keratometer). All eyes were examined and determined to be free of corneal degenerations, diseases and contact lens related problems. Care was taken to obtain good corneal maps and repeatable readings were obtained for both the EyeSys topographer and the keratometer. All measurements for this study were collected by one examiner and with the same keratometer and topographer to help reduce measurement error. The measurements were made using an Bausch and Lomb keratometer and the EyeSys Corneal Analysis System version 3.1. The information from this study was then given to a separate examiner to perform the data analysis.