A single progressive lens has many powers; hence it has many ideal base curves, increasing in lens curvatures from top to bottom. The distance power area calls for a flatter curve, while the near zone calls for a steeper curve.
When a free-form progressive lens is processed using a spherical lens blank, the various powers must share a single base curve, one that may not be ideal for the either zone.
GO CS+ lens blanks feature a variable base curve with front surface innovation that provide the ideal curve in all viewing zones. Leading to unequalled vision at all distances.