What Is PD And Why Is It Important?

  • BY Matthew Surrence

importance of pulpilary distance

This question comes from a recent chat we did on our Facebook page.

Janean Nichole Beri asks, “what is PD and is it important?”

Well Janean, thanks for the great question! PD means “pupillary distance,” which is the distance between the center of each pupil. This is needed to make a pair of Rx glasses, because it tells the manufacturer of the glasses where to put the optical center on each lens. If the PD is wrong, or as we say in the optical world, “out of tolerance,” you won’t be able to focus your eyes together properly.

Often, eye doctors won’t provide the PD to the customer. They always have to provide it to the optician who is going to make the glasses.

However, some eye doctors know that if a customer asks for the PD, they are ordering their glasses online, and savings hundreds of dollars from the huge markups from local optical retailers. If the eye dr. has a relationship with a local optical retailer, they may be reluctant to give their customer the PD, which would take business away from the local optician.

I must stress, Janean, that guessing at the PD number is not the way to go. If the PD isn’t accurate, you wouldn’t be able to see well with the glasses, and you may feel one eye being “pulled” away from the optical center on the lens.

A PD must be measured accurately for the glasses to be accurate. Because we know that many eye doctors decline to provide the PD to their customers, we have the solution!

On our website’s homepage, on the right-hand side of the page, you’ll see WATCH OUR HOW TO VIDEOS. The second video on the list is Measure your PD (Pupillary Distance). I’ve posted it below for convenience though:

This video tells you what you need to know. We also have a link to a downloadable PD ruler on the right-hand side of our website’s home page under QUICKLINKS.

And in the column at the bottom of the right-hand side of the homepage, under the heading INFOGRAPHICS, we have an infographic that explains How to Measure Your PD (in fact, that’s what this infographic is called).

Janean, if you can’t see well with your glasses when you get them, please call Zenni Optical’s customer service line, 800-211-2105, and we’ll be more than happy to assist you in sending these glasses back, and when we get them back, issuing you store credit to purchase another pair of glasses with your accurate PD – which you can get by calling your eye dr. or having a friend or family member (or yourself, if you’re brave!) measure your PD.

Good luck!