1. A cataract surgery microscopy system comprising a microscopy optics ( 5 ) for generating an image ( 58 ) of an object plane ( 9 ) of said microscopy optics ( 5 ) and a pattern generator ( 63 ) for generating a pattern ( 71, 65, 77, 54 ) superimposed on said image ( 58 ), said pattern generator ( 63 ) being configured to generate a ring pattern ( 71 ) with at least one adjustable diameter.