Contact lens base curve

Base curve (BC) describes the curvature of the surface of the contact lens. This curve should correspond to the curvature of the cornea so the lens can fit correctly. The position of the lens on the cornea should be measured by an optometrist with a slit lamp.

Many contact lenses offer 2 or 3 options of curvature so they are suitable for most wearers. Some newer, more flexible models of lenses have only one option of curvature. The numerical value is measured in millimetres, and is most often 8.4mm or 8.6mm (less frequently 9.0mm or 9.1mm).