Pupillary Distance, PD for short, is simply the distance between the centers of the eye pupils measured in millimeters. This measurement is used to position the lens in the frame. Most kid’s PDs range between 40mm and 54mm. In order to successfully measure your child’s PD you need two things: a camera and a personal card (ID, credit card, bank card, driver’s license etc.). Any of those cards are usually 3 3/8″ (86mm) wide and it is used to compare it with your kid’s PD.
Here are 6 steps to take this measurement: