When I first started EM, I looked at my two pairs of expensive glasses from fancy optometry shops (where the PD number is of course as secret as the Nuclear Code), and neither of them had the PD number on them. So I did a quick measurement with a ruler and ordered my first normalized. I’ve now run through a whole bunch of glasses (since I have ordered multiple pairs for each diopter that I’ve gone through) and merrily used the PD measurement that I came up with that first time.
In the back of my mind, though, I’ve kept wondering if maybe I should have a more accurate less home-made measurement.
Today I learned about this dandy Android app (since I have a new Android phone after a series of eight iPhones—and, yes, I feel like a heretic after years of Apple orthodoxy in all my devices), and it tells me I’ve been WAY off: it gives me a PD of 68.5mm. I’ve been ordering glasses with 74mm PD!
My current normalized (two pairs) are pretty new. Is it important for me to ditch them and get ones with the 68.5 PD?