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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 ...
Optical aberration. 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]
In order to see a clear image, the eye must focus rays of light on to the light-sensing part of the eye - the retina, which is located in the back of the eye.This focusing - called refraction - is performed mainly by the cornea and the lens, which are located at the front of the eye, the anterior segment.
Condenser (optics) A condenser is an optical lens that renders a divergent light beam from a point light source into a parallel or converging beam to illuminate an object to be imaged. Condensers are an essential part of any imaging device, such as microscopes, enlargers, slide projectors, and telescopes. The concept is applicable to all kinds ...
In visual perception, the near point is the closest point at which an object can be placed and still form a focused image on the retina, within the eye 's accommodation range. The other limit to the eye's accommodation range is the far point . A normal eye is considered to have a near point at about 11 cm (4.3 in) for a thirty year old. [1]
Subjective refraction. 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.
In people with Cushing syndrome, “too much cortisol leads to a more rounded face, pinkish red cheeks, thinner skin with easy bruises, a puffy neck, and a worsening upper back hump,” Dr. Ghalib ...