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).