Segment height

Segment Height (also referred to as Seg Height or SH), measures the distance from the bottom of the lens to the top of the bifocal line or the start of the progressive power of a multifocal lens. Thus, seg height measurement only applies for bifocals or progressive lenses and single vision lenses do not have a segment height glasses measurement. The seg height for bifocal or multifocal lenses is specific to each pair of glasses, meaning that the bifocal segment height of your lenses may not be the same between pairs of glasses.