The invention concerns a method for operating a projection exposure apparatus to project the image of a structure of an object (5) arranged in an object plane (6) onto a substrate (10) arranged in an image plane (8). The object (5) is illuminated with light of an operating wavelength of the projection exposure apparatus according to one of several adjustable exposure modes. The light produces changes in at least one optical element (9) of the projection exposure apparatus, by which the optical properties of the projection exposure apparatus are influenced. The operation of the projection exposure apparatus makes allowance for the influencing of the optical properties of the projection exposure apparatus or a quantity dependent on the former, being calculated approximately on the basis of the exposure mode used and the structure of the object (5).