For your new spectacles to be made accurately, we will need the distance in millimetres between the centre of your two eyes. For those who have a combined prescription of more than + or – 2.00 we insist on having your P.D measurement as it is in your best interest. We want you to be happy with the spectacles you purchase from us and an incorrect P.D measurement, especially in higher prescriptions, could make them uncomfortable to wear.
All is not lost however. It is easy to obtain this, just ask a friend to hold a millimetre rule just above the centre of your eyes and measure the distance between your pupil centres. This can sometimes be tricky with large pupils or dark coloured eyes, an easier method it to measure the outside edge of one pupil to the inside edge of the other pupil, as shown in the picture below. Working in good light will also make measuring easier as the pupils will be less dilated.
Both of you should be at the same height approximately, sat opposite each other. The measurer holds the ruler in their left hand across the bridge of your nose and closes their LEFT eye to avoid any parallax error. With their RIGHT eye open, they then first line up the ruler with outside edge of your left pupil. Then without moving the ruler they close their RIGHT eye and with their LEFT eye read off the measurement to the inside edge of RIGHT pupil. (See diagram)
You should fix on an object. E.g. the open eye of the measurer. This should ideally be about 40 centimetres, 16 inch (400mm) away.
This measurement will ensure the accuracy of your spectacle lenses when supplied.
A typical measurement will usually be somewhere between 55mm and 72mm
Print off this guide and keep it to hand, just in case you need to refer back to it. Take the measurement two or three times to get an average and to ensure accuracy.