PD stands for Pupillary Distance. It is a kind of measurement about the distance of your pupil. You can ask your optician to check it. However, sometimes there is No PD for you from Opticians . To overcome your problem, you should visit Zenni: the #1 online eyeglasses store . In this site, you will get information about: What is PD? For further information, visit Zennioptical.com.