Let me confess that I don’t know my PD (Pupillary Distance) - the distance between the pupils of the eyes, center to center, in Millimeters (1 inch = 25.4mm) – though I am using prescription eyeglasses for some time now. No one ever told me that till the time I explored Zenni: the #1 online eyeglasses store and found out what is PD and why professional eye care providers must provide you this vital information to get the right eye glasses. I suggest that you don’t take No PD for you from Opticians in future. And when you have all the information, go to Zenni and they will make perfect prescription eye glasses that are just right for you and your eyes.