The present invention is directed to an arrangement by which the image field of the illumination components and irradiation components of ophthalmic instruments for diagnosis and therapy is improved. In the arrangement according to the invention, one or more diffractive optical elements is/are arranged additionally in the illumination beam path for deliberate shaping of the image plane in the eye to be irradiated. These diffractive optical elements can be located on the surface of other optical elements, swiveled into the illumination beam path, and their wavelength changed by filters. The image plane can be adapted to the spherical contour of the eye so that the projected characters and structures have a uniformly high image quality in the center and in the edge area of the eye. The present invention is applicable for variable illumination for diagnosis and treatment of the eye, in particular for irradiation of the eye lens and other parts of the eye such as the cornea or retina. The arrangement can be used in a great variety of ophthalmic instruments such as fundus cameras, slit lamps, laser scanners, OPMI instruments or surgical microscopes.