How to take your pupillary distance

How to take your pupillary distance
Your interpupillary distance is a basic optical measurement that basically calculates the distance between your pupils. This measurement is generally necessary when purchasing ophthalmic lenses to ensure that the lenses will be positioned properly in front of your pupils. Correct positioning is necessary to receive the best vision correction. To measure it, you can do it yourself or with the help of a friend.

All you need is this:

Position a ruler (in millimeters) to the bridge of your nose.
Have your friend stand in front of you at about an arm's length away, positioning the "0" of the ruler in the center of your left pupil.
Your friend should measure the distance from that point to the center of your right pupil.