Pupillary Distance and How to Measure It

Have you ever experienced trying on a pair of eyeglasses and you suddenly felt a sting on your eye? This is called an instant eye strain. The reason behind this is that your pupillary distance could have been measured inaccurately.

Pupillary Distance

What is Pupillary Distance (PD)?

Your pupillary distance (PD) is the distance between your pupils that determines the comfort and how well your glasses fit. An accurate measurement of PD is just as important as your eyeglasses prescription.

The average pupillary distance for an adult person is approximately 63 mm, but this does not mean you can guesstimate this number. Measurements vary widely between 51 mm and 74.5 mm for women and 53 mm and 77 mm for men.

There are two primary methods to measure PD.

  • Single PD (Binocular PD) is the distance from one pupil to another between each eye.
  • Dual PD (Monocular PD) is measured from your nose bridge to each eye

Dual PD is considered to be the most accurate since many people find their nose-to-pupil measurement not equidistant on both sides. PD is essential in fitting glasses with progressive lenses that require precise lens-to-pupil alignment to guarantee a comfortable vision at all distances.

Pupillary Distance

How to Measure Pupillary Distance

Your eye doctor usually measures PD as part of your routine eye exam through a pupillary distance ruler or a corneal reflex pupillometer. But the good news is that you can measure your own PD in a pinch using only a millimeter ruler and a mirror.

Stand around 8 inches away from a mirror while holding the ruler just above your eyes and flat against your eyebrow. Close your right eye, and align the ruler’s zero mark to the center of your left eye. Without moving the ruler, close the left eye and record the distance from your ruler’s zero to the right pupil. Voila! This distance is now your pupillary distance measurement to make it easier for you to order glasses online. Take note that if you are farsighted or are measuring for reading glasses, you have to subtract 3 mm.

You may want to repeat these steps a number of times to ensure the most accurate PD measurement. However, a do-it-yourself pupillary distance calculated with a ruler will not be as accurate as the PD measurement you will get from your eye doctor. For the best glasses to fit the distance between your eyes, schedule an eye exam.

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