Single Vision lenses only require your PD (pupil distance). Multi-Focal lenses like Progressives, Bifocals and Trifocals require you to have your Distance MONO PD measured, and dot the pupil center on each lens with a permanent marker on the frames being used for new lenses. Following is detailed instructions for obtaining this information.
Pupillary Distance, Pupil Distance or PD
If you're ordering lenses for a new frame, you will need to provide your Distance MONO PD (monocular pupil distance). Have your doctor include this on your prescription or have a local eye care professional measure this for you. A MONO PD measurement only takes a minute and there is usually no charge for this service.
If the frames you're sending us for replacement lenses have your existing prescription lenses, they have been working well and they are the same lens type as the lenses you're ordering (progressive, bifocal, trifocal or single vision) then dotting your pupil center is not necessary. (We will fit the new lenses with the same fitting information as your old lenses).
Fitting Height or Segment Height
Dot the pupil center on each lens with a permanent marker. This can be done in front of a mirror or by having another person do it for you. Be sure to keep your head still while passing the pen from one eye to the other and keep the dot small. Dotting the lenses is used for the vertical placement of a progressive, bifocal, trifocal and some single vision lenses and is not considered an accurate PD measurement.
If your frames do not have any lenses in them at all (prescription lenses, demonstration or dummy lenses) you can place clear tape over the right and left lens opening of the frame as a surface to draw the dots.