A method of determining an ophthalmic prescription (Rx) for a patient's eye, includes obtaining a wavefront measurement of the patient's eye; determining a first Rx for the patient's eye from the wavefront measurement, the first Rx corresponding to a maximum value of a merit function calculated from the wavefront measurement of the patient's eye for a first size of the pupil of the patient's eye; determining one or more additional Rx's of the patient's eye for one or more additional pupil sizes different from the first pupil size, wherein each additional Rx is determined for a corresponding size by calculating a value of the merit function for the previously-calculated Rx at the corresponding size and searching for an Rx at the corresponding size that provides a larger value of the merit function than the previously-calculated Rx at the corresponding size; determining a final Rx based on the first Rx and the additional Rx's; and outputting the final Rx.