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Base curve radius (BCR) or simply base curve (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 (BCOR). Typical values for a contact ...
Astigmatism causes difficulties in seeing fine detail. Astigmatism can be often corrected by glasses with a lens that has different radii of curvature in different planes (a cylindrical lens), contact lenses, or refractive surgery. [5] Astigmatism is quite common. Studies have shown that about one in three people suffers from it.
Base curve: BOZD Back optic zone diameter BOZR Back optic zone radius BVP Back vertex power CLAPC/CLIPC Contact-lens-associated/induced papillary conjunctivitis CLARE Contact-lens-associated red eye CLPU Contact-lens-associated peripheral ulcer Dk Unit of permeability DW Daily wear EW Extended wear FOZD Front optic zone diameter FVP
Aspherics are only [citation needed] used for corrective lenses when, in order to achieve a flatter lens for cosmetic reasons, the lens design deviates from the best-form sphere; this results in degradation of the visual correction, degradation which can, in some part, be compensated for by an aspheric design. The same is true for atoric and bi ...
Contact lenses made from these materials are called rigid gas permeable lenses (RGPs). A rigid lens is able to cover the natural shape of the cornea with a new refracting surface. This means that a spherical rigid contact lens can correct corneal astigmatism. Rigid lenses can also be made as a front-toric, back-toric, or bitoric.
Subjective Refraction is a technique to determine the combination of lenses that will provide the best corrected visual acuity (BCVA). [1] It is a clinical examination used by orthoptists, optometrists and ophthalmologists to determine a patient's need for refractive correction, in the form of glasses or contact lenses. The aim is to improve ...