What is a PD measurement?

 

What is a PD measurement?

A common question is related to a "PD" or "Pupilary Distance" measurement.

It's one of the numbers asked for when filling out your prescription. Problem is, not all prescriptions have it written down. It's the distance between the centers of your pupils (the black part of your eyes), in millimeters (mm).

Normally, when you buy glasses in a local store, this is something they measure. Therefore, optometrists tend to leave it out when writing your prescription.

So what do you do about the PD if you want to buy glasses online and you don't have the PD?

There are a few options:

• Ask your optometrist - they often have it in their records (even though it's not on your prescription). In many places, they're required by law to give it to you if you ask. Better yet, ask them to write it down when you go for your check-up.
• Take it yourself - it's possible to take it yourself using a ruler and a mirror. Stand close to the mirror, line up the ruler, and look straight ahead. Close one eye, and look at the mm measurement with the open one. Switch eyes and do it again. The difference is your PD measurement. Do this a few times to make sure you get accurate results. There are often better instructions with pictures on retailer sites, but this should give you an idea.
  
• Have a friend take it - this is almost identical to the method above, but with a friend taking the measurements while you look straight ahead.
• Use the default - this is not usually recommended, but it may be close enough to work for most people using single-vision lenses. Retailers often list a default of "63mm" which is the average PD for most people. Some retailers suggest that using the default one is fine, which it may be - but note that if yours varies significantly from the default, you may have issues.

Further details about taking our own measurement can be found half-way down the Glasses ABC's page. Once you've got your PD measurement, check out EyeglassRetailerReviews.com for a list of glasses retailers as well as reviews!