2.4K views · 28 reactions | Pupillary Distance (PD) is the distance, in millimeters, between the center of one pupil to the center of the other. The PD is needed to manufacture your eyeglasses because it determines the exact optical center of the lens, which is the point where you look through the lens. Note: the average PD is between 54 and 78mm. | Zeelool | Facebook

Some helpful tips and common mistakes made when new opticians use a millimeter ruler or PD stick to take measurements. | Laramy-K OpticianWorks