The segmentation height, often referred to as Seg Ht, is the vertical measurement from the bottom of the lens in your frames to the center of your pupil. This measurement is essential for progressive lenses as it indicates where the magnification zone will begin.
Unlike your Pupillary Distance measurement, which stays consistent from one pair of glasses to the next, the segmentation height is specific to each frame and its wearer. It’s important that you use the frames that you’ll be sending to us for lens replacement in order to take this measurement.
Measuring your Segmentation Height is pretty simple using our downloadable instructions and millimeter ruler below. However, we do recommend taking this measurement several times or enlisting the help of a friend to make sure the measurement remains consistent each time. Also, make sure you’re standing in your most neutral and natural posture. This will help accurately place the progressive in the most usable area for you.
We see segmentation height measurements most often between 15mm - 28mm. If the measurement is too high in the lenses, this can compromise your distance vision. If the measurement is too low, the magnification portion of the lenses will be inaccessible for your intermediate or reading use. If you’re having trouble feeling confident about the measurement you’ve taken, feel free to contact us and we would be happy to assist.
To find your segment height for progressive lenses, please use the instructions and downloadable ruler here: