How is segment height determined for progressive/bifocal lenses?

by Jason

Segment Height, also commonly referred to as Seg Height, is the vertical measurement in millimeters from the bottom of the lens in your frames, to the beginning of the progressive addition on a progressive lens, or the top line of a lined bifocal.

At Lensabl (and most online glasses/lenses retailers), we request your Seg Height measurements to ensure that your lenses are crafted exactly right for you.

Seg Height Measurements
Self Segment Height Measurement

All you need is a camera, standard wallet-sized card (ID, Drivers License, Grocery Store Member Card, etc), and the frames you need the measurement for.

  1. Make sure you’re wearing your glasses.
  2. Place the card horizontally under your nose, pressed against your mouth.
  3. Grab your camera and snap a selfie!
  4. Our Lab experts will work their magic to determine an accurate Segment Height measurement.

If you are unable to provide a segment height photo or you sent in your frames before taking the SH photo,  we can still get the measurement. We have our own proprietary formula for determining segment height based off the size of the frame and your PD.


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