1. A method for aligning a diagnostic iris image of a patient's eye having a dilated pupil with a treatment iris image of the eye having a constricted pupil, via an iris pattern recognition technique, wherein an iris recognition landmark in the dilated pupil diagnostic image is not directly identifiable with the corresponding iris recognition landmark in the constricted pupil treatment iris image, characterized by: visibly illuminating the patient's eye with a plurality of selected levels of visible illumination to effect a corresponding plurality of different pupil sizes ranging from a constricted pupil diameter to a dilated pupil diameter; respectively obtaining a sequential plurality of diagnostic iris images each of which has an indicia of the iris recognition landmark; correlating the indicia of the iris recognition landmark in each sequential diagnostic iris image such that the iris recognition landmark in the constricted pupil diagnostic iris image is identifiable with the iris recognition landmark in the dilated pupil diagnostic iris image; making a diagnostic measurement of the patient's eye and the associated diagnostic image when the pupil is dilated; obtaining a treatment iris image of the patient's eye having a constricted pupil; aligning the constricted diagnostic iris image with the constricted pupil treatment iris image.