Your interpupillary distance is a basic optical measurement that basically calculates the distance between your pupils. This measurement is usually necessary when purchasing ophthalmic lenses to ensure that the lenses will position themselves 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 about an arm's length away by positioning the “0” on the ruler in the center of your left pupil.
  • Your friend should measure the distance from that point to the center of the right pupil.