last word

By Karlen McLean, ABOC, NCLC

High-Tech Lens Dictionary

Some lens definitions remain unchanged, but it never hurts to refresh old standbys. Plus with the advent of new fabrication and lens technologies, there are some new ones to learn as well.
Abbe value: The amount of chromatic aberration (distortion) inherent in the material. Low Abbe=higher chromatic abberation, high=lower.
Aspheric. Non-spherical. Aspheric lenses reduce peripheral astigmatism.
Atoric: Lenses with a spherical front surface with aspherized cylinder curves on the back surface.
Chromatic aberration. Peripheral color fringes or distortion of light at different rates (dispersion). Digital surfacing, direct-tosurface processing, and free-form. Lens production process combining patient Rx, optical measurement, and software calculation.
Refractive index. Measurement of how a lens material refracts or bends light.
Wavefront. A method of analyzing and measuring light waves to determine the geometry of the cornea and eye aberrations.

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