The invention relates to an apparatus and a method for determining the applicability of a treatment pattern for manipulation of a cornea of an eye using a laser. The concept of the present invention is based on the determination of an actual volumetric profile based on a set of input data and a theoretical volumetric profile which is created independently based on only the basic optical parameters. On the basis of a comparison of the determined volumetric profiles it is determined whether the actual volumetric profile is within predetermined tolerances.