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The Four Prism Dioptre Reflex Test (also known as the 4 PRT, or 4 Prism Dioptre Base-out Test) is an objective, non-dissociative test used to prove the alignment of both eyes (i.e. the presence of binocular single vision) by assessing motor fusion. [1]
Hutton's definitions in 1795 [4]. The ancient Greek mathematician Euclid defined five types of quadrilateral, of which four had two sets of parallel sides (known in English as square, rectangle, rhombus and rhomboid) and the last did not have two sets of parallel sides – a τραπέζια (trapezia [5] literally 'table', itself from τετράς (tetrás) 'four' + πέζα (péza) 'foot ...
Prism correction is commonly specified in prism dioptres, a unit of angular measurement that is loosely related to the dioptre. Prism dioptres are represented by the Greek symbol delta (Δ) in superscript. A prism of power 1 Δ would produce 1 unit of displacement for an object held 100 units from the prism. [2]
The definitions and results in this section are taken from the 1913 text Plane and Solid Geometry by George A. Wentworth and David Eugene Smith (Wentworth & Smith 1913).. A cylindrical surface is a surface consisting of all the points on all the lines which are parallel to a given line and which pass through a fixed plane curve in a plane not parallel to the given line.
The glasses are placed in the trial frames with the striations vertical, giving rise to two horizontal line images when viewing a spotlight. If the patient has a vertical deviation, the lines will be seen one above the other. If there is little or no vertical separation, vertical prism can be used to separate the lines.
Surveying prism pole with instrument attached. In surveying, a pole is bar made of wood or metal and normally held vertical, upon which different instruments can be mounted: a prism, a GPS device, etc. [1] It may be manufactured with a predetermined length (e.g., 2 meters) or may be graduated for different heights or stages.
As a result, the vertical axis is a 2n-fold rotoreflection axis. D nh is the symmetry group for a regular n-sided prism and also for a regular n-sided bipyramid. D nd is the symmetry group for a regular n-sided antiprism, and also for a regular n-sided trapezohedron. D n is the symmetry group of a partially rotated prism.
The prism paralleloscope entered service with the British Army in the late 1950s. It was permanently fitted in a fibre-glass case with a lid. This case was mounted on two short metal vertical poles so that it was about 2 ft (0.6 m) above the ground, these vertical poles were held together by two horizontal rods slightly shorter than the paralleloscope case.