Grinding two separate curves on the front side of a lens is referred to as what?

The process of grinding two separate curves on the front side of a lens is known as plus cylinder grinding. This technique is typically employed to create a lens with a specific prescription that incorporates astigmatism correction. In plus cylinder grinding, one curve is often spherical while the other is cylindrical, allowing for different focusing abilities across the lens surface.

In contrast, concave grinding refers to creating a surface that is inwardly curved, while convex grinding pertains to producing an outwardly curved surface. Bifocal grinding is focused on creating lenses that offer two distinct optical powers, commonly for near and distance vision, but does not specifically address the grinding of two separate curves on the same side of a lens.

Thus, plus cylinder grinding accurately describes the process involved in shaping the lens to serve the corrective needs for astigmatism as required in various visual prescriptions.