dysmetropsia

dysmetropsia
   The term dysmetropsia comes from the Greek words dus (bad), metron (yardstick), and opsis (seeing). It is used to denote a distorted perception of image size. The term dysmetropsia was introduced in or shortly before 1916 by the British neurologist Samuel Alexander Kinnier Wilson (1878-1937) to replace the older term "dysmegalopsia. Wilson defines dysmetrop-sia as a defect in the visual appreciation of the measure or size of objects, whether by over-estimation or by under-estimation. On phenomenological grounds, dysmetropsia is commonly divided into four categories, comprising "macropsia, "micropsia, "pelopsia, and " teleopsia. However, combinations and intermediate forms (such as "porropsia, "microtelepsia, and " macroproxiopia) have been described as well. Using the alleged locus of origin as a guiding principle, Wilson divides dysmetropsia into a peripheral and a central form, and the latter into a cortical and a transcortical (or psychical) form. As noted by Wilson, dysmetropsia may occur physiologically (i.e. in the case of objects appearing larger through a fog, and in the case of the "Moon illusion), but also in the context of disease (notably tabes dorsalis, syphilitic basal meningitis, epilepsy, hysteria, tic disorder, alcoholism, and retinal conditions such as retinitis, and sarcoma of the choroid). Dysmetropsia is generally classified as a "sensory distortion, more specifically, as a variant of "metamorphopsia. However, in some hierarchical models it constitutes a class of its own, ranking at the same level as the metamorphopsias. Wilson himself motivates this arrangement by pointing out that metamorphopsias are characterized by a distortion of the visual image, whereas dysmetropsia involves a change in estimated size, without any kind of distortion of the interrelationships between the image's constituent parts.
   References
   Frassinetti, F., Nichelli, P., di Pellegrino, G. (1999). Selective horizontal dysmetropsia following prestriate lesion. Brain, 122, 339-350.
   Wilson, S.A.K. (1916). Dysmetropsia and its pathogenesis. Transactions ofthe Ophthalmological Society UK, 36, 412-444.

Dictionary of Hallucinations. . 2010.

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  • dysmetropsia — dys·met·rop·sia (dis″mə tropґse ə) [dys + Gr. metron measure + opsia] defect in the visual appreciation of the measure or size of objects …   Medical dictionary

  • Micropsia — An illustration depicting the symptoms of micropsia from Lewis Carroll s 1865 novel Alice s Adventures in Wonderland. ICD 10 H …   Wikipedia

  • dysmegalopsia —    The term dysmegalopsia comes from the Greek words dus (bad), megas (big), and opsis (seeing). It translates roughly as the diminished ability to appreciate the size of objects. Dysmega lopsia is generally classified as a sensory distortion or …   Dictionary of Hallucinations

  • teleopsia —    Also known as teliopsia and telopsia. All three terms stem from the Greek words tèle (far), and opsis (seeing). The term teleopsia was introduced in or shortly before 1949 by the British neurologist Macdonald Critchley (1900 1997) to denote a… …   Dictionary of Hallucinations

  • macroproxiopia —    The term macroproxiopia comes from the Greek adjective makros (large), the Latin adjective prox imus (near, nearby), and the Greek noun opsis (seeing). It refers to a visual distortion in which the perceived size and distance of objects is… …   Dictionary of Hallucinations

  • macropsia —    Also known as macropsy, macroptic vision, megalopsia, and megalopia. The term macropsia comes from the Greek words makros (large) and opsis (seeing). It refers to a visual distortion in which objects and stimuli are perceived as… …   Dictionary of Hallucinations

  • metamorphopsia —    The term metamorphopsia comes from the Greek words metamorphoun (to change the form) and opsis (seeing). It translates roughly as seeing an altered form . It is not clear who introduced the term, but it appears in a medical lexicon as early as …   Dictionary of Hallucinations

  • micropsia —    Also known as micropsy, microptic vision, Lilliput sight, Lilliput vision, and lilliputianism, after the fictitious country featuring in the novel Gulliver s Travels by the Irish poet and author Jonathan Swift (1667 1745). The term micropsia… …   Dictionary of Hallucinations

  • microtelepsia —    The term microtelepsia comes from the Greek words mikros (small), tèlè (far), and opsis (seeing). It refers to a variant of *dysmetropsia in which the perceived size and distance of objects is altered, in the sense that objects are perceived… …   Dictionary of Hallucinations

  • pelopsia —    The term pelopsia comes from the Greek words pelorios (peculiarly large) and opsis (seeing). It is used to denote a visual distortion in which stationary objects appear to be closer than they are. Pelopsia is classified either as a… …   Dictionary of Hallucinations

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