The device has a light source (12) for producing an illumination ray bundle for illuminating an eye that is to be observed, where the illumination ray bundle runs coaxial to an observation ray bundle. An illumination optic (11) is designed in accordance to a Koehler illumination principle. A reflex lens aperture (18) is provided in the illumination optic, where the reflex lens aperture covers reflex light that is radiated from the surface of a lens unit (19). The reflex lens aperture is arranged in an illumination ray path in front of a superimposition unit (20).
