PD:pupillary distance 

What is a single PD or dual PD?

A single PD is the measurement, in millimeters, from the center of one pupil to the center of the other.
A dual PD is the measurement of the center of each pupil to the center of the bridge of your nose.

Pupillary distance is an important measure used to determine the proper lens shape and align your prescription corrections with your line of sight. If there is no accurate partial discharge measurement, vision correction may be difficult because the lenses need to be centered in the pupil to ensure clarity.

Dual PD is the measurement from the center of each pupil to the center of the bridge of your nose

For example:

A dual pd prescription
pd left : 32mm right:31.5mm  on your prescription

A single pd prescription
pd left : 31.5mm right:31.5mm  on your prescription
or
pd: 63mm

What is my pupillary distance (PD) and how do I get it?

Your pupillary distance (PD) is the measurement of the distance between your pupils.  This is needed for the manufacturer of the eyeglasses to know where to place the optical center on each lens, so you can see well with the glasses.

Measure PD Yourself:

1.   Place a millimeter ruler directly under the center of your right or left pupil so that the ruler is horizontal. Stand in front of a mirror, or ask someone else to measure for you.

2.   While looking straight ahead, measure the distance from the center of your left pupil to the center of your right pupil.

3.    Repeat a couple of times for accuracy and use an average for your final measurement.

* Note that the average PD is between 57 and 65mm. For bifocal and free-form progressive lenses, two PD values are needed.

Measure PD by myself

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