Pupillary Distance or PD is the distance between pupil centers of your eyes in millimeters.  Also known as Binocular PD. Monocular PD is needed if your eyes are not equal distance from your nose. Right eye (OD PD) and left eye (OS PD) are measured from the center of your nose to each pupil.  

PD is needed to accurately center the lens in the frame you select

For bifocals or progressive lenses, some people will need a Distant Vision PD (DV PD) and a Near Vision PD (NV PD).  This is because some peoples eyes converge when looking at near objects.   PD measurements are essential for all spectacle dispensings, monocular PDs being essential in progressive lenses and for those with high prescription. PDs can be measured using a pupilometer or by using a ruler. 

- Normal PD for adults range from 58 to 70mm.

Frame Sizing:

Measurements For Glasses ( eye, bridge, temple, vertical )

• Width or Eye Size- refers to the horizontal width in millimeters of one of the frame's lenses.

• Bridge Size- measurement is the distance in millimeters between the two lenses. It is measured between the two closest points of the two lenses.

• Temple or Arm Size- is measured along the length of the temple, from one end to the other.  This includes any curvature.

• Vertical Height (B)- refers to the vertical height of an eyeglasses lens, and is measured from the tip to the bottom of the lens aperture of the frame. The measurements are taken from a horizontal line intersecting with the top of the lens, to the horizontal line intersecting with the bottom edge of the lens. The B measurement is only important when ordering multifocal lenses.

(Often the measurements do not include Vertical height)

Using your existing glasses to get your current sizing: 

Most name brand glasses have sizing information printed on the inside of the frame or bridge.  Sometimes this is the first part to wear away.