LENS DESIGN

SAGITTAL DEPTH

Another important concept to 
understand with contact lens fitting 
is sagittal depth.  With a curved 
surface of a certain radius and chord 
diameter, it will have a given sagittal 
depth (see #1) which can be 
mathematically determined.  One can 
think of the sagittal depth of a 
contact lens as the distance from a 
flat surface the lens is resting on up 
to the back surface of the lens.

The steeper the radius, the greater 
the sagittal depth (S ) if the chord 
diameter is not changed (see #2).

If the radius of a curve is not changed 
but the chord is made larger, the 
sagittal depth (S ) will be greater 
(see #3).