ASPHERIC LENSES


Most contact lenses are made with 
spherical base curves, the radius 
of curvature is the same over the 
whole base curve area.

Some lenses are made with 
aspheric curves.  In this case the 
radius of curvature gradually 
changes from the center of the 
lens towards the periphery.  The 
radius usually becomes longer away 
from the center.

The radius at the very center of an aspheric lens is called the apical radius.