Base curve radius


Base curve radius, or simply base curve, abbreviated BCR or BC, is the measure of an important parameter of a lens in optometry.
On a spectacle lens, it is the flatter curvature of the front surface.
On a contact lens it is the curvature of the back surface and is sometimes referred to as the back central optic radius. Typical values for a contact lens are from 8.0 to 10.0 mm. The base curve is the radius of the sphere of the back of the lens that the prescription describes. This number is important in order to allow the contact lens to fit well to the wearer's cornea for comfort, to facilitate tear exchange, and to allow oxygen transmission.
The United States Food and Drug Administration states that, "Contact lenses can be used to correct a variety of vision disorders such as Myopia, Hyperopia, Astigmatism, and Presbyopia."