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HOW TO MEASURE
PUPILLARY
DISTANCE
(PD)

What is PD?

Your Pupillary Distance, or PD, is the distance in millimetres (mm) between the centre of one pupil to the centre of the other. A personalised fit starts with measuring your pupillary distance: it indicates which part of the lens you look through, ensuring optimal comfort and clarity.

Why is it important?

If your PD isn’t right, it can cause eye strain, fatigue or simply not being able to see properly. The higher your prescription, the bigger the effect an incorrect PD can have. So get measuring!

WHAT IS SINGLE VS DUAL PUPILLARY DISTANCE?

Single PD

SINGLE PD is the pupillary distance between the centre of one pupil to the other, which can be a distance PD or near PD. Distance PD can be used to order any type of prescription glasses except reading glasses. Read below to learn how to calculate near PD for reading glasses.

Dual PD

DUAL PD, or monocular PD, consists of two numbers and is the distance between the centres of each pupil to the bridge of the nose. Dual PD is usually written in the following notation: 32/30. The first number is always the right eye (OD) measurement, and the second number is the left eye (OS).

HOW TO GET YOURS?

You can ask your Optometrist to include your PD measurement on your prescription, or if you don’t have it, you can use one of the following methods to measure.

With the Opthy App

By yourself

With the help of a friend

Start using Opthy

With just a few clicks, Opthy measures your Pupillary Distance allowing you to find the most comfortable, personalised fit.

DISCOVER MORE

Meets industry guidelines for accuracy (ANSI Z80.1 and ISO21987 standards)

Opthy on iPhone X

Download the app

App available on iPhone X and above.

Opthy on iPhone X
Opthy on iPhone X

Scan the QR code and download the app.

App available on iPhone X and above.

Opthy on iPhone X

Problems with the QR code? See the app on the App Store.

By yourself

You will need a mirror, something to note information down and a ruler marked in millimetres
(Don’t have one? Download it here)

1

Position yourself

Position yourself approximately 30 cm away from a mirror. Look straight ahead into the mirror and place the ruler over the bridge of your nose.

Do you already own a pair of glasses?
Wear them during this step.

2

Measure

Close your left eye and align the 0 mm over the centre of your right pupil. Measure the distance from the centre of your right pupil to the centre of your nose. Repeat with your left eye.

If you are wearing your glasses you can use an erasable marker to draw the point directly on the lens.

3

Write it down

If the PD value is the same for both eyes, add them together to get a single PD. If the PD values are different, mark both values. This means you have a dual PD and you will need to enter them separately.

With the help of a friend

You will need a friend, pencil and paper and a ruler marked in millimetres
(Don’t have one? Download it here)

1

Face your friend

Make sure your friend is standing in front of you, at a 40 - 50 cm distance (it should be the length of your friend’s arm stretched out).

2

Centre your ruler

Have your friend align the ruler over the bridge of your nose. The 0 mm should be over the centre of your right pupil.

Do you already own a pair of glasses?
Wear them during this step.

3

Measure

Look straight ahead and have them measure from the centre of your right pupil to the centre of your nose. Repeat for your left eye.

If you are wearing your glasses you can use an erasable marker to draw the point directly on the lens.

4

Write it down

If the PD value is the same for both eyes, add them together to get a single PD. If the PD values are different, have your friend mark both values. This means you have a dual PD and you will need to enter them separately.

FREQUENTLY ASKED
QUESTIONS

Knowing your Pupillary Distance is a requirement when buying glasses. Opthy allows you to determine your PD or verify existing measurements to proceed smoothly with your online purchase. Don’t need glasses right now? No problem - you can still keep track of your PD value for future needs.
No, your PD value is not available directly on your current glasses.
If you ever had an eye exam, the value could be found on your prescription, but it is not always provided there.
Opthy operates within a specific range of PD values to give an optimal and personalised experience consistent with the best standards in the industry.
With the current version of the application, Opthy only measures your Far Pupillary Distance.
Stay tuned for further developments.
Opthy is intended for single vision lenses within a certain prescription strength range (+/- 5 diopters). It is not compatible with higher-powered prescriptions, bifocals, progressives or multifocal.
Not intended for use by people under the age of 18.
Eye test

HAVING TROUBLE MEASURING YOUR PD?

Book an eye test at your nearest OPSM store and let our optometrists help you

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