PUPILLARY DISTANCE (PD) measures the distance between the centers of your pupils. This is known as an "Optical Center". This measurement is used to determine where you look through the lens of your glasses and should be as accurate as possible.
Your prescription may tell you your PD. But if the PD is not available, use a buddy or a mirror to help you figure it out.
STEP ONE
Stand about 8” away from a mirror. Grab your small ruler in one hand. Have your a place ready to write down the information. Look straight ahead into the mirror and position the ruler over the bridge of your nose.
STEP TWO
Starting with the right eye, line up the zero end of the ruler at your pupil; measure the distance from your right to your left pupil. The millimeter number that lines up with your left pupil is the measurement you want. That number is your PD. Write this down. Just to be sure, measure a few more times to make sure you get the same number. You want it to be accurate. (This Is Very Important!)
STEP ONE
Grab friend, a small ruler marked in millimeters, a pencil & paper.
STEP TWO
Have that friend hold the ruler up to your right so the zero end lines up with your pupil. Measure the distance from your right to your left pupil. The number that lines up with your left pupil is your PD. Write it down. Try it a couple times to make sure your measurement is accurate.
STEP THREE
Repeat And High Five You Are Done!
References
