A method and system for measuring an optical property of a multi-focal lens are disclosed. One embodiment of the method comprises: filtering out light transmitted by all but one of a plurality of diffraction orders of the lens to provide an unfiltered light from a single diffraction order; receiving the unfiltered light at a wavefront detector; and analyzing the unfiltered light at the wavefront detector to measure the optical property. The multi-focal lens can be a multi-focal diffractive intra-ocular lens. The measured optical property can be a discontinuity in the lens surface. Filtering can comprise blocking all but the unfiltered light using an aperture operable to let through the unfiltered light from the single diffraction order, and/or blocking all but the unfiltered light using an opaque obstruction operable to let through only a selected amount of light corresponding to the light transmitted by the single diffraction order. The method can further comprise generating an image quality parameter, such as a modulation transfer function, based on the measured optical property.