to measure, its easy if u have a pupilometer.. but if u have a pd stick, a small ruler with mm scale, u cna measure the center or one pupil to the other.. as for seg height.. if its bifocal, measure up to the lower eye lid.. as for single vision such as near sighted or far sighted, just measure directly the center of the pupil.. progressives are the same but you have need to make sure the frame is big enough to accomadate it