Read the markings as frame dimensions
Numbers such as 52–18–140 usually describe lens width, bridge width and temple length in millimeters. Markings may be on an arm, on the bridge or split across locations. They help compare frames; they are not a measurement of the wearer’s pupils.
Keep fit and PD separate
Two people can wear the same frame model and need different PD values. A comfortable bridge is useful information when shopping, but it does not reveal where the optical centers should be placed for a particular wearer. Record frame dimensions in a different place from your optical measurements.
Use a useful comparison
Photograph the model name and dimensions of an existing comfortable pair. Compare those with the listed dimensions of a new frame. Also consider the bridge construction and overall front shape, since similar numbers do not guarantee identical fit. Ask for help when choosing a very different style.
Complete the order honestly
If the only numbers available are inside your frames, leave the PD question unresolved and ask your optician. Do not add the lens and bridge widths to invent a PD. Our helper can organize a measured value once you have it.
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PD formats
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Put this guide to work
Compare the relevant frames and ordering details before choosing your pair.