1. The arrangement for carrying out a surgical treatment of an eye, comprising: a diagnostic instrument adapted to register eye-structure data, a data processing unit adapted to generate, on the basis of the eye-structure data registered by the diagnostic instrument, a structural image that contains at least one mapping of a characteristic eye structure and also at least one positional marking arranged relative to the mapping of the characteristic eye structure, the structural image comprising, as the mapping of the characteristic eye structure, a mapping of at least one of a blood vessel, an iris structure, an iris margin, and a limbic geometry against a transparent background, and an image-data fade-in device which is adapted to fade the structural image generated by the data processing unit into an image generated by a surgical microscope during the implementation of a surgical treatment of the eye.