Abstract

The evaluation of the topography of the anterior surface of human corneas has up till now relied hevily on the use of Placido's disk. This method has certainly helped physicians to diagnose some refractive diseases and be more confident about the outcome of refractive surgery. For many years the evaluation was only qualitative, but in recent years it has become quantitative. Today, powerful commercial systems are present in all the relevant institutions. Recently, the main limitations of systems based on Placido's disk have been recognized and there are serious efforts to improve or substitute it with systems based on different principles. Several proposals for new systems have been made ranging from interferometry^1,2, to the rasterstereographic imaging³. One main drawback of all of these methods, however, including that based on Placido's disk, is that they take one image of all the points at once. In most cases this is not a problem, but when the anterior corneal surface present severe deformations, it is difficult or impossible to compute its shape.

© 1996 Optical Society of America