Understanding Pupillary Distance and How to Measure It

Added: 04-23-2023, Views: 332

Pupillary Distance (PD) is the measurement of the distance from the center of one pupil to the other. It is a simple but crucial measurement when shopping for glasses online because it’s the method used to ensure that the lens’s optical center is properly positioned over the pupil.

There are instances where people’s eyes are not perfectly symmetrical. In such cases, people measure the distance from the bridge of the nose to the center of each eye. This method, referred to as dual pupillary distance (DPD), typically results in a better fitting lens because each eye has been measured accurately, despite the lack of symmetry.

There are several ways to measure this distance at home. Technology is available that can figure out the distance with a card with a magnetic strip and a webcam. You could also measure PD with your Smartphone or with a ruler. Still another way, if you’re in a pinch, is to use an old pair of glasses.

How to Measure Pupillary Distance Using Old Glasses

Put your glasses on and stand 8 to 10 inches away from a mirror.
While staring straight ahead, use a non-permanent marker to mark where the center of your pupils lines up with your glasses. Good potential choices for your non-permanent marker would be a washable or dry erase marker, or a highlighter. Keep those pesky sharpies away from your lenses so they can’t do any permanent damage.
At this point, you’re ready to measure the distance between the dots, at which point, you’ll have your PD measurement.
Just to repeat, this is the least accurate method of determining your PD measurement. A way to add a bit more accuracy is to have somebody else make the marks for you. Just make sure they have the right non-permanent marker in their hand.

FAQs

What if the PD Is Not Measured Correctly?

The PD for most adults is between 52-72mm. Most males end up on the higher end (56-72mm) while most women end up on the lower end (52-64mm). The average PD for men is 64mm, while the average PD for women is 62mm.

Does Your PD Measurement Ever Change?

Your PD does change as you grow from a child into an adult but it is extremely unlikely that there would be further changes after puberty. This can work in your favor, though, as once you get the correct measurement once, as an adult, you’ll never have to take the PD measurement again.

How Accurate Are PD Measurements?

When performed by an optometrist, PD measurements are almost always perfectly accurate. If you do your own, at home, you do not have to be 100 percent accurate. Though it can tolerate a small error range, it is recommended that you attempt several measurements to ensure accuracy.

What if Your PD Is Too Small for Your Frame?

Now that you know what is pupillary distance, you might ask about the frame of the glasses. Experts expect the pupils to sit slightly closer to the inside of the frame than the outside, but close to the center of the lens. If you have a PD of 40, you will need a frame with a smaller PD and if you were to try on frames with a PD of, say, 60, your vision would be affected as though you were cross-eyed.

PD measurements ensure that your vision remains clear and there are several ways to make sure that they’re done correctly, even if you’re at home, purchasing prescription safety glasses online. Visit the Marvel Optics website today and check out their current inventory of sunglasses so that your precious eyes will be protected tomorrow.