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Corrective lens. A corrective lens is a 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 worn on the face a short distance in front of the eye.
Abbe number. In optics and lens design, the Abbe number, also known as the V-number or constringence of a transparent material, is an approximate measure of the material's dispersion (change of refractive index versus wavelength), with high values of V indicating low dispersion. It is named after Ernst Abbe (1840–1905), the German physicist ...
In optics, chromatic aberration ( CA ), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. [ 1][ 2] It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent ...
An optical instrument is said to be diffraction-limited if it has reached this limit of resolution performance. Other factors may affect an optical system's performance, such as lens imperfections or aberrations, but these are caused by errors in the manufacture or calculation of a lens, whereas the diffraction limit is the maximum resolution ...
1: Imaging by a lens with chromatic aberration. 2: A lens with less chromatic aberration. In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. [ 1] Aberrations cause the image formed by a lens to be blurred or distorted, with the ...
The small improvement in depth of focus with the conventional IOLs enhances uncorrected near vision and contribute to reading ability. Wavefront customized lenses can be used in eyeglasses. Based on Wavefront map of the eye and with the use of laser a lens is shaped to compensate for the aberrations of the eye and then put in the eyeglasses.
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.
Wavefront-guided LASIK is a variation of LASIK surgery in which, rather than applying a simple correction of only long/short-sightedness and astigmatism (only lower order aberrations as in traditional LASIK), an ophthalmologist applies a spatially varying correction, guiding the computer-controlled excimer laser with measurements from a ...
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