PD is the measure of the Distance between the pupil in one eye to the center of the pupil in the other eye. It should be part of your prescription details, and therefore we highly recommended you request this PD value from your optician. *NY and MA residents must have their PD measured by a doctor or licensed optician. To Measure your Pupillary Distance (PD): Place the simple mm ruler on the top of this page over the bridge of your nose so that the starting point of the ruler is exactly at your left or right eye pupil. Keep the scale straight. Stand in front of a mirror of ask a friend to measure the distance between the pupils while you look straight ahead. Repeat this three times for accuracy. In most cases, PD value ranges between 57 mm to 65 mm with most common being 63 mm. You may find your PD presented as 63/61. This means the Distance PD is 63 and the near PD is 61. When ordering single vision lenses only the distance PD is required. For bifocals and progressives, please also provide the near PD.