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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.
A telescopic sight, commonly called a scope informally, is an optical sighting device based on a refracting telescope. [1] It is equipped with some form of a referencing pattern – known as a reticle – mounted in a focally appropriate position in its optical system to provide an accurate point of aim.
Chromostereopsis is a visual illusion whereby the impression of depth is conveyed in two-dimensional color images, usually of red–blue or red–green colors, but can also be perceived with red–grey or blue–grey images. [1] [2] Such illusions have been reported for over a century and have generally been attributed to some form of chromatic ...
Prism adaptation. Prism adaptation is a sensory-motor adaptation that occurs after the visual field has been artificially shifted laterally or vertically. It was first introduced by Hermann von Helmholtz in late 19th-century Germany as supportive evidence for his perceptual learning theory (Helmholtz, 1909/1962). [1]
Evil eye. A person from Cairo, reputed to possess the evil eye. The evil eye is a supernatural belief in a curse brought about by a malevolent glare, usually inspired by envy. [1] The belief in the evil eye among humans has existed since prehistory, [1] and amulets to protect against it have been found dating to about 5,000 years ago. [1]
Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing the power of the lens relative to ...
LCD projector. An LCD projector is a type of video projector for displaying video, images or computer data on a screen or other flat surface. It is a modern equivalent of the slide projector or overhead projector. To display images, LCD ( liquid-crystal display) projectors typically send light from a metal-halide lamp through a prism or series ...
A tribrach is an attachment plate used to attach a surveying instrument, for example a theodolite, total station, GNSS antenna or target to a tripod. A tribrach allows the survey instrument to be repeatedly placed in the same position over a surveying marker point with sub- millimetre precision, by loosening and re-tightening a lock to adjust ...