what is pupillary distance used for
Pupillary distance (PD) is the measurement (in millimeters) of the distance between the pupils of your eyes. Pupillary distance is an important measurement used to determine the proper lens shape and alignment of your prescription correction to your line of vision.Without an accurate PD measurement, correcting vision can be difficult since lenses need to be aligned over the center of your pupil for proper clarity.he other type of measurement is called monocular, which is a per-eye measurement from the pupil to the middle of the face, this type of measurement will be between 20-40 mm.