Base curve radius (BCR) or simply base curve (BC) is the measure of an important parameter of a
lens
A lens is a transmissive optical device that 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 the healthcare practice concerned with examining the eyes for visual defects, prescribing corrective lenses, and detecting eye abnormalities.
In the United States and Canada, optometrists are those that hold a post-baccalaureate f ...
.
On a
spectacle lens
A corrective lens is a Lens, transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia. Glasses or "spectacles" are wor ...
, 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 (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 transparency (optics), transparent front part of the eyeball which covers the Iris (anatomy), iris, pupil, and Anterior chamber of eyeball, anterior chamber. Along with the anterior chamber and Lens (anatomy), lens, the cornea ...
for comfort, to facilitate
tear exchange, and to allow oxygen transmission.
See also
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Lens shape
*
Radius of curvature (optics)
References
*
External links
Understanding contact lens prescriptions
Corrective lenses
Radii
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