A single progressive lens has many powers; hence it has many ideal base curves, increasing in diopters from top to bottom. The distance zone power calls for a flatter base curve, while the near zone power calls for a steeper base curve. When a free-form progressive lens is processed from a spherical lens blank, the various powers must share a single base curve, one that may not be ideal for the near zone.
The Camber lens blank features a variable base curve, a front surface innovation that provides the optically ideal base curve in all viewing zones.