[Possibilities and limits of marking the visual axis of the cornea using the surgical microscope]

In procedures involving refractive corneal surgery, as in the fitting of conventional optical devices for visual correction, the question of correct centering arises, i.e., the surgeon has to determine and mark the point of intersection of the visual axis on the cornea. The operating microscope, which is in any case used for the surgical procedure, provides the simple means of performing this task. The practical application of this procedure, the theory behind it, and suggestions as to possible instrumentation are the subject of this paper.