Why is PD required when ordering prescription glasses online?

[Dayton]

I was ordering prescription glasses online and it required me to fill the PD. I can not find PD information from my prescription that provided by my doctor.

[Billy]

PD is the distance between the centers of your pupils in millimeters (mm). The optical stores will determine your visual center according to your PD. So your PD is required when you order prescription glasses online, otherwise the glasses won't fit you properly.

[Jonathon]

Yes. PD is very important to make the correct glasses. It is used to determine the central vision in your glasses lenses so that your eyes can see through the central vision exactly.