Pupillary Distance (PD) Measurement
For those who have a prescription of more than + or - 2.50, we will need the distance in millimetres between the centre of your two eyes. It is easy to obtain this, just asks a friend to hold a millimetre rule just above the centre of your eyes and measure the distance between the outside edge of one pupil to the inside edge of the other pupil.
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)
For those who have a prescription of more than + or - 2.50, we will need the distance in millimetres between the centre of your two eyes. It is easy to obtain this, just asks a friend to hold a millimetre rule just above the centre of your eyes and measure the distance between the outside edge of one pupil to the inside edge of the other pupil.
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)
If you are taking the pd
RIGHT PD - Wink ( close ) the left eye - and have your friend look just under your right eye - measure from the centre of the nose to the centre of the pupil ( if you want to be really accurate this is the right pd )
LEFT PD - Wink ( close ) your right eye and ask your friend to look just under your left eye - keeping really still and your nose in line with thier nose read the measuring rule from the centre of the nose to the middle of the left pupil.
BINOCULAR PD - if your precription is low and there is fairly even head and eye symetry , the glasses are for distance only; then this meaurement will be fine . Use the diagram to measure that distance shown.
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
The national average is 64 mm for men and 62 for women.
If you can take the average 3 readings that would be even better.
