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Measure your Pupillary Distance

Here at Bailey Nelson we care about your peepers, after all you need them to see all the awesome things you do everyday. To ensure we get your prescription sitting perfectly in your lenses we need something called a Pupillary Distance Measurement (or PD for short). We know it’s a mouthful but keep reading and you will get your head around it in no time. We also have a nifty online tool to measure this for you in case you don’t live near a Bailey Nelson store, or are too busy to pop in.

So what is a Pupillary Distance Measurement?

Your PD is the distance between the centre or your right and left pupils. We use this measurement to ensure that your prescription is sitting exactly where your eye needs it in your frames and not off to the side or below your line of sight. Your eyes should view the world through the best part of your lenses and since your pupils are in the middle of your eye, we make your lenses with that central point in mind. That’s why we can’t make up your unique prescription lenses until we have this measurement.

Why is a PD important?

Well apart from the fact that you might not have that 20/20 sight you are after if your PD isn’t right, it can cause eye strain, fatigue, or even double vision with higher prescriptions. All glasses are produced for optimal performance. We do this by fitting lenses to the frame so that the lens centres match your PD. Also the higher your prescription, the bigger the effect an incorrect PD can have.
So now that you are a PD pro, get measuring! And don’t forget: if something doesn’t feel right, you can always contact us at with your questions or for corrections and we will be more than happy to help you out.

How to measure your PD

Use our tool when you're entering your prescription during the checkout process for the quickest way to figure out your PD. Get your laptop or phone camera ready and follow these instructions:

  1. Rest your phone or computer on a steady surface in a well-lit room.
  2. Turn up the volume, so you can listen to to the instructions.
  3. Look directly into the camera, not at yourself.
  4. If you wear glasses, take them off.
  5. Grab your bank card (or any card with a magnetic strip). Light coloured cards work best
  6. Click start scan - making sure you've allowed access to your camera
  7. Hold the card by its top corner and hold it flat on your forehead. We might ask you to make small adjustments.
  8. Once you have done this, you'll have your PD. Make sure to write it down to enter it with you prescription details at the checkout

Tips to keep in mind:

Whilst the distance between your pupils is one length, you'll have to halve it to work out the PD for each eye, e.g. if your PD is 60mm, your left and right eyes will be 30mm each.

If you can't halve your PD to a round number, no problem -split them to the closest 0.5mm, e.g. if your PD is 60.5mm, fill in: right = 30mm, left = 30.5mm. We see this quite a bit so, don't worry, we know how to deal with it.

The average PD is somewhere between 59-68mm. If yours falls outside this, or you have a prescription over +/-6SPH, get in touch with us and we'll give you a helping hand.