[Comparative studies with various corneal topography measurement 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 not always satisfied.

MATERIALS AND

METHODS

Five different ring projectors were compared. Spherical and aspherical ball standards were used to measure the standard deviation of the refraction of the system. A patient 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 devices was determined.

RESULTS

The measurement accuracy for ball standards for the five devices was below 1/8 D. For the in vivo case in the control group it was below 1/4 D for four devices. Furthermore, the reproducibility of the results, the accuracy of angle determination and the influence of mechanical and optical design will be discussed. The study demonstrates applications and limits of this measurement method.