For buying new prescription glasses, you need to know your PD measurement which is the pupillary distance. It is the distance from the centre of the black circular area of the pupil to the centre of the other eye’s pupil.

This measurement allows lens technician to fit the lenses in the glasses in such a way so that when you wear your glasses, you are then automatically looking through the centre of the lens thus to achieve the correct vision.

In case if your optician does not provide you with a PD measurement, here are some tips to help you out to measure your PD.

Things that you need to measure PD:

A straight “mm” ruler, a pencil or pen

 

1. Take help from a friend or a partner to assist you
2. Focus at a fixed point at some distance like a centre in photo frame
3. While your eyes are fixed at a point, ask your friend to measure the distance between the centre of one pupil to the centre of the other pupil. The distance would be in millimeters. The average PD is normally between 57mm to 65mm. The most common PD reading is 63 mm.
4. If it is difficult to measure the distance from the centre of the pupil, the edge of the
    pupil (the black circular area) may be used as measuring point to the edge of the other pupil as an alternative method. Measurement can be read from the left side of one pupil to the left side of the other pupil.

 

You can use a normal scale to measure the distance. You can place the ruler on the bridge of your nose. Always ask your friend for measuring your PD distance as this would allow to take accurate readings. You can repeat the procedure three times to take accurate readings. Match the readings with the previous readings for better results.