Base curve radius
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Base curve radius or simply base curve, abbreviated BCR or BC, is the measure of the general shape of a lens in optometry. On a spectacle lens, it is the flatter curvature of the front surface and on a contact lens it is the curvature of the back surface. Typical values 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. Lenses must fit well to the wearer's cornea in order to be comfortable and to facilitate tear exchange and oxygen transmission.
In everyday practice, if lenses feel "loose" and slide easily a smaller base curve may work better. A large base curve may be needed if they feel tight. Lenses with smaller base curves are referred to as "steep".
See also
External links
- OptiCampus.com
- Understanding contact lens prescriptions
- Contact Lens Prescriptions Explained (detailed article about contact lens prescriptions)