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A corrective lens is a lens worn on or before the eye. They are used to treat myopia , hypermetropia , astigmatism , and presbyopia . The main article for this category is Corrective lens .
PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies ...
The prism is also less bulky than the double Porro design. The prism is sometimes simply called a "roof prism", although this is ambiguous, because other roof prisms exist, such as the Amici and Schmidt–Pechan designs. A variant of the Abbe–Koenig prism replaces the "roof" section of the prism with a single mirror-coated reflecting surface.
The strength of the prism is increased until the streak of the light passes through the centre of the prism, as the strength of the prism indicates the amount of deviation present. The Maddox rod is a handheld instrument composed of red parallel plano convex cylinder lens , which refracts light rays so that a point source of light is seen as a ...
These are low dispersion glass, most notably, glasses containing fluorite. These hybridized glasses have a very low level of optical dispersion; only two compiled lenses made of these substances can yield a high level of correction. [9] The use of achromats was an important step in the development of optical microscopes and telescopes.
An ideal trial frame have minimum 3 cells, one each for holding spherical lens, cylindrical lens and other tools like occluder or pinhole. [4] Angle for axis of astigmatism is marked on outermost visible cell There are knobes to adjust pupillary distance, side angle, height and cylindrical lens axis. [5]
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