Measuring and fitting
Monocular PD
Optical glossaryMeasuring and fitting
Your PD measured separately for each eye, from the nose bridge. More accurate than a single figure, and required for individualized lenses.
Illustrative · the shape of the principle, not measured data
In more depth
Faces are rarely symmetrical: one pupil often sits a millimeter or two further from the center of the nose than the other. A monocular PD records each eye's distance from the bridge separately, so each lens is centered on its own eye rather than on half of a total.
For single vision lenses the difference is usually small. For progressives it decides whether each corridor runs straight down the line the eye actually travels when reading — a corridor set off to one side narrows the usable view on that eye.