With high minus lenses the edges become too thick and uncomfortable. In this case a
second curve is cut in the
periphery on the front surface
of the lens to thin the edge.
This is called a minus lenticular
lens.
For hydrogel lenses, due to their large diameter, this is necessary for low minus lenses. For RGP lenses over about -5.00 D to -6.00 D a lenticular cut is needed.