An evaluating unit which is adapted to determine a degree of an instantaneous overlap between an optical zone of the eye and the structure, or at least a part of the structure effecting refractive correction, based on a recorded image. By determining the degree of overlap between the instantaneous optical zone and the structure to be introduced, it is possible to control the superposition of the optical zone with the tissue volume which is specifically altered by means of the laser cutting and, accordingly, to enable a maximum coverage.
