How to Measure Pupillary Distance

Pupillary distance is the length between the centers of the two pupils. 

The purpose of measuring pupillary distance is to ensure that eyeglasses fit comfortably and align with the center of the wearer’s eyes. A pair of glasses that does not take pupillary distance into account would potentially be uncomfortable or even harmful. 

Monocular vs. Binocular Pupillary Distance Measurement

There are two types of pupillary distance measurement, and each serves a unique function.

Monocular Pupillary Distance Measurement

Monocular pupillary distance measurement is sometimes referred to a single pupillary distance measurement. With this type of measurement, the distance between the center of one pupil and the other is measured. 

A monocular pupillary distance measurement provides a single number in millimeters.

Binocular Pupillary Distance Measurement.

Binocular pupillary distance measurement is sometimes referred to as a dual pupillary distance measurement. With this type of measurement, the distance between the center of each eye and the bridge of the nose is measured. 

Binocular pupillary distance measurement allows for enhanced customization, alignment, and comfort, as eyes tend to not be perfectly equidistant and symmetrical. The result of a binocular pupillary distance measurement is two numbers in millimeters, noting the distance of each eye from the bridge of the nose.

Looking for the Best LASIK Near You?

Find a LASIK Surgeon

How to Measure Pupillary Distance

Pupillary distance can be done professionally using specialized equipment, but you can obtain a reasonably accurate estimate of this distance with a simple ruler and mirror. This section contains a list of steps needed to measure pupillary distance at home. 

Steps for Taking a Monocular Pupillary Distance Measurement

Follow these steps to take a monocular pupillary distance measurement at home:

1. Position yourself in front of the mirror, close enough to where you can clearly make out the readings on a ruler. 
2. Line the ruler across the bridge of the nose and with the readings below the eyes, aligning the zero with the center of the pupil of one eye.
3. Document the number of millimeters displayed on the ruler below the center of the pupil of the other eye. For example, one person’s monocular distance reading may be 61mm.

Steps for Taking a Binocular Pupillary Distance Measurement 

1. Position yourself in front of a mirror as you would when performing a monocular pupillary distance measurement. 
2. Line up the ruler across the bridge of the nose with the 0 end of the ruler at the center of one pupil. 
3. Document the number of millimeters showing on the ruler at the center of the bridge of the nose.
4. Repeat these same steps for the other eye and record both, separated by a forward slash. For example, a binocular pupillary distance measurement may read 31/30 mm. 

Apps to Help Measure Pupillary Distance 

There are several apps for both iPhone and Android that can help measure pupillary distance. 

EyeMeasure is one app available that allows users to measure pupillary distance. GlassesOn is the highest-ranked app for measuring pupillary distance, and it also claims to be the only medical grade app available for this function. GlassifyMe also developed an app, available on both iOS and Android, for measuring pupillary distance. 

Each of these apps has different benefits and features. It is best to try them out and compare them for yourself to determine which is best for you. Some apps contain in-app purchases and allow for subscriptions that add to the benefits and functionality that users can access. 

Pupillary Distance FAQs

Is there an app that measures pupillary distance?
Yes, there are numerous apps that can measure pupillary distance. Examples include GlassesOn, EyeMeasure, and GlassifyMe.

Can I measure my pupillary distance at home?

Yes, you can measure pupillary distance at home. All you need is a mirror and a ruler.

References

1. How to Measure Pupillary Distance. (2022). LensCrafters.

2. Mobile Apps for Your Eyes. (2022). GlassifyMe.

3. EyeMeasure. Apple Store.

4. GlassesOn. Google Play.

5. Evaluation of Pupillary Distance (PD) Measurement Using Smartphone-Based Pupilometer. (June 2021). Journal of Physics.

6. The Reliability, Validity, and Normative Data of Interpupillary Distance and Pupil Diameter Using Eye-Tracking Technology. (July 2017). Translational Vision Science & Technology.

7. Measurement of Unique Pupillary Distance Using Modified Circle Algorithm. (January 2018). International Journal of Computer Applications.