What term refers to an approximation of lens surface curvature marked on the lens box?

The term that refers to an approximation of lens surface curvature marked on the lens box is known as the nominal curve. This term is commonly used in the optical industry to describe a standard or reference curvature that is applied to lenses. The nominal curve provides important information regarding the curvature of a lens surface, which is essential for proper fitting and prescription accuracy.

Understanding the nominal curve is crucial for opticians and lens manufacturers, as it allows them to estimate how the lens will perform optically when placed in front of the eye. This approximation helps in the selection of lenses that best match the visual needs of the wearer. The nominal curve serves as a baseline that can be referenced when designing or ordering lenses, ensuring consistency and quality in lens production.