Base Curves & Safety Glasses

Safety glasses are available as prescription and non-prescription, also called "plano" lenses. All lenses have a curve, and the front lens surface is called the base curve. The base curve is convex, or pushes outward.

Significance

• The curve of a lens affects how you see through the glasses. Non-prescription and prescription safety lenses alike have curves. The greater the number in the base curve, the more curved the lens looks.

Types

• Safety glasses are made from three types of lens material: glass, plastic or polycarbonate. The curve on each material varies depending on the person's prescription, the size of the frame and other factors decided by the eye doctor during an eye examination.

Warning

• Be careful when reading an eyeglass prescription to determine base curve. The term "base" may be written on a glasses prescription in one of two ways. Base is used with "Base Curve" for the curvature of a lens, but also for "Base Up" or "Base Down," which pertains to prism and thickness of a lens, and is unrelated to curvature.