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.
How to Measure Segment Height:
Step 1: Set the Stage
Position yourself in a well-lit room with your mirror and materials at the ready.
Step 2: Put on Your Glasses
Wear your pair of glasses. This will be your guide to getting the perfect fit.
Step 3: Find Your Pupils
Look straight ahead into the mirror and mark the center of each pupil with a small dot or sticky note. These marks are your starting points.
Step 4: Measure Down
Using your ruler or measuring tape, measure downward from each pupil mark to the bottom of the lens. This distance is your segment height. Attention: the measurement refers to the bottom of the lens, not the frame.
Step 5: Record and Repeat
Note down the segment height for each eye. For accuracy, repeat the process a couple of times to ensure consistency.
Step 6: Double-Check for Symmetry
Check that the segment heights for both eyes are symmetrical. If not, make slight adjustments until you achieve balance.
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