what is pupillary distance

What Is Pupillary Distance and How to Measure PD

When purchasing a pair of prescription eyeglass online, you need to know some professional terms first, such as Sphere, Cylinder, Axis, Pupillary Distance, and so on. Hence, this post will focus on the professional term – Pupillary Distance(PD).

What Is Pupillary Distance?

Pupillary distance, also referred to as pupil distance or PD, is the distance between the center of each pupil and the bridge of your nose measured in millimeters. Pupillary distance is very important for making prescription glasses because it is used to determine where you look through the lens of your glasses, so it should be as accurate as possible. If the pupillary distance is not accurate, the prescription power of your lenses will be off-center from your eyes and you won’t be able to see out of your glasses.

In addition, the average adult’s pupillary distance is between 54-74mm, and the average kid’s pupillary distance is between 43-58mm.

After knowing what the pupillary distance is, do you know how to measure pupillary distance? So, in the following part, we will show you the methods.

How to Measure Pupillary Distance?

In general, after an eye exam, you will get the pupillary distance. An optician will measure your pupillary distance with a high-precision measuring device called pupillometer.

However, you can also measure the pupillary distance by yourself. So, here, we will show you how to do that. Before doing that, you need to prepare a millimeter and a mirror. 

Now, here is the tutorial.

  1. Stand about 8 inches away from the mirror.
  2. Hold a ruler against your brow.
  3. Close your right eye and then align the 0mm on the rule with the center of your left pupil.
  4. Then look straight, close your left eye and open your right eye.
  5. Check the millimeter which is aligned with your right pupil. The total distance is your pupillary distance.

After all steps are finished, you have measured your pupillary distance by yourself. But for ensuring its accuracy and precision, you had better measure 3-4 times.


Single PD vs Dual PD

From the above part, you have known what the pupillary distance is. But, there are some differences between single PD and dual PD.

Single PD: single PD is the pupillary distance between the center of one pupil to the other. It can be a distance PD or near PD. It can be used to order prescription glasses except for reading glasses.

Dual PD: dual PD, also called monocular PD, consists of two numbers and is the distance between the centers of each pupil to the bridge of the nose. The dual PD is usually written as follows: 32/30. The first number is usually the PD of the right eye and the latter one is the PD of the left eye.

To sum up, after reading this post, you have known what the pupillary distance is and how to measure pupillary distance. If you just need a pair of glasses, try Koalaeye Optical. If you have any different idea of the pupillary distance, leave a message in the comment zone. If you have any problems with glasses, feel free to contact us via the email service@koalaeye.com.

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