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).