PD stands for Pupil Distance can also be known as OC’s - Optical Centres. These are the distances between your pupils meaning that the lenses are set at the correct distance apart.

MEASURING YOUR PD (PUPIL DISTANCE)

Your PD is simply the distance between the approximate centres of the PUPILS of your eyes (the black circles in the centres of your eyes), measured in millimetres. Ideally your optician will measure this and supply you with the reading, but it is not a legal requirement for them to do so.

However it is easy for a friend to measure your PD for you. Just get them to stand directly facing you and with the ruler touching your nose, place the start of the millimetre scale in line with the pupil centre of the right eye. Then simply read off the measurement of where the centre of the pupil of the left eye lies along the scale (see diagram below which measures 62mm).