1. A cataract surgery microscopy system comprising: a microscopy optics including an objective lens and an ocular for generating an image of an object plane of said microscopy optics, wherein a semitransparent mirror is disposed in a beam path between said objective lens and said ocular; and a pattern generator for generating a pattern superimposed on said image, said pattern generator being configured to generate a ring pattern with at least one adjustable diameter, wherein said pattern generator includes a display to display said pattern and a projector to project said pattern displayed on said display towards said ocular via said semitransparent mirror.