What is Segment Height (SH)?
Segment Height, also known as Seg Height or SH, 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. Segment height does not apply to Single Vision lenses. The determined Segment Height is specific to each frame and wearer.
Our lab has over 50 years of optical experiencing with creating progressive lenses. We use a very accurate progressive lens formula that is precisely calculated to the frames you order. Our formula is accurate is most cases.
If you would like to measure your own segment height then you will need to have the frame in hand, because you can only measure it while the glasses are on your head. You can either purchase the frame without lenses first (click "Add Frame Only" on the product page) and then send them back to have lenses put in after the segment height has been measured. Or if you have already received your glasses and feel the segment height is not correct, you can use the frames you already have.
How do I measure my own Segment Height?
Follow the instructions below to measure your own Segment Height at home.
FREE SH RULER (Adobe Reader required.)
- Download the Segment Height Ruler above, or use a ruler that has millimeter measurements. You can also use a ruler with centimeter measurements and simply times the result by 10 to get your millimeter measurement.
- Put the glasses on your face and adjust them so that they sit comfortably.
- Stand about 8 inches (20 cm) away from a well lit mirror with your face parallel and square to the mirror.
- Align the ruler's zero (0) measurement to the lowest point at the bottom of your lens, keeping it exactly vertical. Make sure you are measuring from the bottom of the clear lens, not the bottom of the frame (see graphic above).
- Stare straight ahead and read the millimeter line that lines with the center of your pupil. This is your segment height measurement for these frames.
- Repeat these steps at least 3 to 5 times to get an accurate and consistent measurement. Make sure your head and the ruler do not move after lining up the zero (0) measurement with the bottom of your lens until you note your measurement. Ask a friend to help if you are having trouble.