So, first thing’s first: what is papillary distance (PD)? Essentially, it’s the distance between the centers of your pupils (the black bits in the middle of the eyes). Your PD is an
important measurement when your glasses are being manufactured, to make sure you're
looking through the best spot in your lenses for clear vision.
If you don't have a copy of an accurate PD measurement from your optician, you could try to
measure this yourself, or have a friend help you out. We’ll talk you through how to do it here.