The pupillary distance is the measured distance between the pupils of both your eyes. When glasses are made, they need to be created to correct for your eye separation. Some people have wide-set eyes and other have near-set eyes, so this can vary widely. This measurement is made by your optician after you pick a new glasses frame, and the measurement is used when your lenses are cut and fitted into the frame. Normally, your “PD” measurement is not measured by your optometrist/ophthalmologist during a clinic visit and so is not written on a glasses prescription (and thus is not part of your medical records). There is a good reason for this – glass “fitting measurements” need to be made by the same person who actually constructs your glasses and the proper fitting of glasses is somewhat dependent upon what frame and glasses style you are actually buying. Some people would like to obtain their PD measurement so they can order glasses online, as overseas spectacles can be found for surprisingly low cost. Local opticians don’t like to measure the pupillary distance and just “give out” this measurement for someone else to use. In fact, in some states, they aren’t allowed to as it would make them responsible for the glasses (no matter who made them). This reticence on the part of local opticians is not from “greed” or “obstinance,” but an attempt to avoid the inevitable backlash from angry online customers. Online glasses are often made to substandard standards in Indonesia/China with lower quality frames. These glasses can be uncomfortable or cause eye strain because of incorrectly cut PD correction and a poor-fitting frame. Also, foreign producers don’t measure your vertex distance (the distance from the eye to the back of the glass), bifocal segment height, or adjust your progressive lens placement. If a customer receives a pair of crummy glasses in the mail, there is no easy way to “fix” them online … so the only recourse is to return to the local optical shop to complain and try to get them adjusted or remade. This creates unnecessary contention between the customer and optical workers who end up spending inordinate amounts of time trying to fix crummy glasses for free that they didn’t even make (glasses that might even break during the adjustment process with no way to replace them). This situation is comparable to seeing a local tailor/dressmaker and getting measurements for a dress/tuxedo, ordering an outfit from China, and then complaining to your local tailor/dressmaker when it doesn’t fit well. Poorly fit mail-order glasses are more common if you have a “strong” glasses prescription or finicky bifocal requirements. Some people have great success with online sellers, but buyer beware. It is always safer to get your glasses locally … even if you have to shop around a little to find acceptable costs. This way you can try on the frame to get one that is comfortable, get your eyes measured by the shop that actually uses their own measurements, and have them adjusted afterwards (or even completely remade if necessary) without feeling guilty.