COMPARATIVE-EVALUATION OF DIFFERENT CORNE AL TOPOGRAPHICAL DEVICES

Purpose: It is difficult to measure the topography of the cornea with high resolution and visualize it on a map displaying refraction. This is demonstrated by the ongoing improvement and further development of different methods and by the fact that users of these techniques are n ot always satisfied. Materials and methods: Five different ring projec tors were compared. Spherical and aspherical ball standards were used to measure the standard deviation of the refraction of the system. A p atient group of eight people with healthy eyes was used to compare the measurement accuracy and operational errors. Some patients were also measured after cataract surgery. The lateral and axial range of the de vices was determined. Results: The measurement accuracy for bail stand ards for the five devices was below 1/8 D. For the in vivo case in th e control group it was below 1/4 D for four devices. Furthermore, the reproducibility of the results, the accuracy of angle determination an d the influence of mechanical and optical design will be discussed. Th e study demonstrates applications and limits of this measurement metho d.