Attachment module for a microscope, having an ophthalmoscopic lens (142; 242; 342) and an inverting device (140; 240; 340) for inverting an image of an object (143; 243; 343) that is to be observed generated by means of the ophthalmoscopic lens, wherein the inverter device comprises at least four deflection surfaces (146a, 146b, 146c; 246a, 246b, 246c; 346a, 346b, 346c, 346d) by means of which observation beam paths (102) which emanate from the object to be observed can be introduced into a main objective (110) of the microscope, at least two deflection surfaces being planar and at least two further deflection surfaces being non-planar, particularly spherical or in the shape of free-form surfaces.