Base curve radius, or simply base curve, abbreviated BCR or BC, is the measure of an important parameter of a
lens
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
in
optometry
Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities. Optometrists are health care professionals who typically provide comprehensive primary eye care.
In the Uni ...
.
On a
spectacle lens
A corrective lens is a lens (i.e. a transmissive optical device) that is typically worn in front of the eye to improve daily vision. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glass ...
, it is the flatter curvature of the front surface.
On a
contact lens
Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...
it is the curvature of the back surface and is sometimes referred to as the back central optic radius (abbreviated BCOR). 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 (the lower the number, the steeper the curve of the cornea and the lens, the higher the number, the flatter the curve of the cornea and the lens). This number is important in order to allow the contact lens to fit well to the wearer's
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
for comfort, to facilitate
tear exchange, and to allow oxygen transmission.
See also
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Lens shape
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Radius of curvature (optics)
References
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External links
Understanding contact lens prescriptions
Corrective lenses
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