Pupillary Distance alias PD is the distance from the centre of the pupil of one eye to the other. PD is necessary for getting eyeglasses, to correct your vision. The measurement plays a vital part in determining correct positioning of your lenses within the frame. Especially, when you are looking for bifocal or multifocal lenses, PD is mandatory.

Steps:

• Stand in front of the mirror, around 8 inches away
• Keep your head straight and hold a millimetre ruler horizontally on the bridge of your nose
• The 0 mm point of the ruler should be in line with the centre of the left pupil (the black dot which you can see inside your eyeball)
• Measure across, from the centre of left pupil to the centre of right pupil. Make sure you hold the ruler steadily. The measurement which you get is your pupillary distance
• Repeat the above step 3, 4 times constantly, so that you get the accurate measurement

That’s it, your PD is ready.

Monocular PD is mostly recommended for more accurate PD. Since both our eyes are generally asymmetrical. Not both the eyes will be at an equal distance from the nose of the bridge. For eg: If the total binocular distance is 58 mm, it is not necessary that it will be equidistant on both sides. From one eye to the nose bridge it might be 31 mm while other it might be 27 mm. This can get the PD wrong. Monocular PD helps to get accurate measurement, especially for crafting progressive lenses.