C
- carrier
- central field
- centration distance CD
- centration error of the instrument
- centration point CP
- clear lens
- coated lens
- combination frame
- concave lens
- condensing lens
- continuously-indicating focimeter
- contrast
- converging lens
- convex lens
- corneal plane
- Corneal Refraction
- corrective lens
- curved-form lens
- curved-top bifocal
- curved-top segment
- cylinder
- cylinder axis
- cylindrical lens
- cylindrical power
- cylindrical surface
- cylindrical test lenses
corneal plane
Plane that is perpendicular to the optical axis of the instrument and that is tangential to the corneal surface closest to the instrument when in normal use.