Your Pupillary Distance
What is a PD and why is it needed to make prescription lenses?
Your pupillary distance (PD) is the distance between the centers (pupils) of your eyes, measured in millimeters. This measurement is used to make prescription lenses. Your PD measurement is used when we take a lens with your prescription and customize it to both fit your frame and you. To be effective, a lens must be cut so the center is directly in front of your pupil. Without your PD we have no idea where that point is for you and as the picture shows everybody is different. You have two different PD\u2019s, distance and reading. Distance is where your pupils are when focusing on an object 20 feet away. Reading is when you are focusing on something about 12-18 inches in front of you this number is slightly lower than the distance as one\u2019s eyes converge or \u201ccross\u201d when looking at something up close. |  |
Ways that PD measurements are read
 | There are two ways to measure a PD, from pupil to pupil which is called bi-nocular or from one pupil to the center of your nose and the other to the same point or mon-ocular. The Bi-nocular is usually within 10mm of 64mm and the monocular is within about 5mm of 31mm per eye. Your doctor or optician may provide it either way, there is no industry standard although mon-ocular is more precise. |
How to measure your own pupillary distance
our Pupillary Distance (PD) is something you can measure yourself with the help of a friend. Your eye care professional can also provide you with this information.
Ask your friend to do the following:
Hold the ruler up to the bridge of your nose.
Have your friend close one eye.
hey should align the ruler's zero on the left, in the center of your pupil. The pupil is the black spot in the middle of the eye.
Without moving the ruler, have them move their head to the right and read the millimeter line corresponding to your other pupil.
Repeat the process two or three times for accuracy.
Record your results.