Soft Contact Lenses – Lens Selection, Paperwork, and Handling Practice Test

Sagittal height describes how much the lens vaults over the cornea, basically how tall the posterior surface is relative to the corneal apex. With a constant diameter, making the fit tighter means the lens must grip the eye more closely along the whole circumference. To maintain contact around the edge while the center is pressed more firmly onto the cornea, the posterior surface effectively needs to be steeper (more curved). That increased curvature raises the sagittal height. If the fit were looser, the back surface wouldn’t need to be as steep, so sagittal height would be smaller or unchanged. So the tighter fit leads to a larger sagittal height.