The Pd or pupillary distance is the [distance] between the center of your pupils measured in millimeters.
This measurement ensures your prescription lenses are correctly centered in front of your eyes when purchasing new glasses
This measurement is especially important for people with higher prescriptions
Your pD is not always given as part of the prescription when you have an eye exam
You should ask your optician for the PD measurement
However the optician testing your eyes is under no obligation to provide it or there may be a small fee
Thankfully you can measure your pD yourself with the help of a friend or a family member
There are two types of PD Measurement. One for distance and one for reading
The distance PD measurement is used for distance
intermediate
bifocal or very focal glasses
The reading PD measurement will be used only for reading glasses
We will show you how to measure both types of PD measurement in this video
The selectspecs PD rule is designed to fit over the bridge of your nose with sections cut out for your eyes to look through
With the help of another person sit opposite each other about an arm's distance apart
your helper should hold the PD Ruler between their thumb and forefinger resting the ruler on the bridge of your nose and
Steadying their hand by placing the remaining fingers against your head
The person taking the measurement should close their right eye and look directly opposite into your right eye
Make sure you look directly into their open eye as you are being measured
Make a mental note of the measurement from the bridge of the nose to the center of the pupil in millimeters
Without moving the PD rule the person taking the measurement should close their left eye and use their open right eye
To look into your left eye directly opposite
Again make sure you look directly into their open eye as you are being measured
Make a mental note of the second measurement from the bridge of the nose to the center of the pupil in millimeters
Now add these two numbers together to get your PD measurement
Repeat the process several times until you are happy with the accuracy of your results
in general an adult Pd measurement or for somewhere between 55 and 72 millimeters
If you don't have a pd ruler you can use a standard Ruler with millimetre measurements
Taking the same positions with your helper as before the person taking the measurement should close their right eye
Using their open left eye
They look directly into your right eye opposite lining up the zero on the ruler with the center of your pupil
Make sure you are looking directly ahead into their open eye as you are being measured
The person taking the measurement should rest the ruler firmly against your forehead to keep it steady
Without moving the Ruler the person taking the measurement should close their left eye and use their open right eye to look into your left
eye directly opposite
Again make sure you look directly into their open eye as you are being measured
The measurement at the center of the second Pupil is your PD measurement
Repeat this process several times until you are happy with the accuracy of your results
Remember to keep your head perfectly still as you are being measured
If you are purchasing reading glasses, you'll need your reading or near PD measurement
The principle for measuring a reading PD is almost identical to measuring a normal distance PD
The person taking the measurement can simply follow the instructions already mentioned in this video
The only difference is that the person being measured should focus on an object closer to their face.
Hold a pen around 30 centimeters in front of your face and keep your focus here while your pd is being measured.
This will cause your eyes to converge slightly giving you a more accurate reading PD measurement
We advise
Against measuring your PD yourself using a mirror because the distance to the mirror surface and your reflection in the mirror can vary
dramatically while taking the measurement which may result in a less accurate PD measurement
If you are not comfortable or confident enough to measure your pD with some help
it is possible to take your measurement from an existing pair of glasses
When placing an order for new glasses you can choose to send your old glasses to us and we can take the measurement from those.
The glasses must include both prescription lenses for a measurement to be possible
Once a PD measurement has been taken from your old glasses
we can even return them or donate them to charity if you no longer need them
Once you know your PD measurement. You should write it down and keep it with your prescription in a safe place
Unlike your prescription the PD measurement won't change over time