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Specialty. Neurology, ophthalmology. Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. [1] Also called double vision, it is a loss of visual focus under regular conditions, and is often voluntary.
Prism dioptres. 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]
Eye care professionals use prisms, as well as lenses off axis, to treat various orthoptics problems: Diplopia (double vision) Positive and negative fusion problems [ambiguous] [citation needed] Prism spectacles with a single prism perform a relative displacement of the two eyes, thereby correcting eso-, exo, hyper- or hypotropia.
Convergence insufficiency. Convergence Insufficiency. Other names. Convergence disorder. Specialty. Ophthalmology, optometry. Convergence insufficiency is a sensory and neuromuscular anomaly of the binocular vision system, characterized by a reduced ability of the eyes to turn towards each other, or sustain convergence .
Peli Lens. The Peli Lens is a mobility aid for people with homonymous hemianopia. It is also known as “EP” or Expansion Prism concept and was developed by Dr. Eli Peli of Schepens Eye Research Institute in 1999. It expands the visual field by 20 degrees. He tested this concept on several patients in his private practice with great success ...
Amblyopia. Anisometropia is a condition in which a person's eyes have substantially differing refractive power. [1] Generally, a difference in power of one diopter (1D) is the threshold for diagnosis of the condition . [2] [3] Patients may have up to 3D of anisometropia before the condition becomes clinically significant due to headache, eye ...
In optics, chromatic aberration ( CA ), also called chromatic distortion and spherochromatism, is a failure of a lens to focus all colors to the same point. [1] It is caused by dispersion: the refractive index of the lens elements varies with the wavelength of light. The refractive index of most transparent materials decreases with increasing ...
Porro prisms are most often used in pairs, forming a double Porro prism. A second prism rotated 90° with respect to the first, is placed such that light will traverse both prisms. The net effect of the prism system is a beam parallel to but displaced from its original direction, with the image rotated 180°. A double Porro system provides four ...
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