Pupillary Distance, or PD, is the distance between the centres of your pupils. The PD is vital as it helps us customise your lenses to align precisely in front of your pupils, enhancing comfort and clarity of vision. It's usually measured in millimetres.
If you don't have this measurement, you can usually get it from your optician or from a previous prescription.
Alternatively, the following apps will usually provide an accurate "self-service" measurement: