corona phenomenon

corona phenomenon
   The term corona phenomenon is indebted to the Latin noun corona, which means crown. It was introduced in or shortly before 1966 by the Danish neuroscientists Axel Klee (1933-1982?) and Rolf Willanger to denote a *visual illusion consisting of an extra edge perceived around objects. The phenomenon itself has been described before, however, andreferredtobysuchtermsas* halo, border, and shiny ring. The German ophthalmologist Christian Georg Theodor Ruete (18101867) has been credited with providing the first written account of a corona phenomenon avant la lettre in 1845. Corona phenomena typically present in the form of a single or a double contour. They can surround objects in whole or in part, can be executed in any type of colour, including black and white, and may take on a shining, silvery, or shimmering quality. They may occur in isolation, or in association with an incomplete loss of vision (i.e. a *scotoma), a * scintillating scotoma, or a complete * hemianopia. In addition, they may be accompanied by * geometric hallucinations. Atypical corona phenomena have been described as well, presenting in the form of multiple coloured edges, multiple waves and zigzag lines, coronas surrounding illusory images, or combinations of corona phenomena and other illusory or hallucinatory phenomena such as *mosaic vision, *autoscopy, *polyopia, *teleopsia, and *micropsia. Etiologically, corona phenomena are associated primarily with * migraine aura and with * sensory deprivation. Their pathophysiology is basically unknown, but it has been suggested that they may be mediated by CNS structures involved in visual contrast perception. The corona phenomenon should not be confused with the corona of light associated with * Buddha's halo, with * heiligenschein, with the * visual halo (also known as corona), and with the * aura featuring in the paranormal literature.
   References
   Klee, A., Willanger, R. (1966). Disturbances of visual perception in migraine. Acta Neurolog-ica Scandinavica, 42, 400-414.
   Podoll, K., Robinson, D. (2001). Corona phenomenon as visual aura symptom in migraine. Cephalalgia, 21, 712-717.
   Ruete, C.G.T. (1845). Lehrbuch der Ophthalmologie für Aerzte und Studirende. Braunschweig: F. Vieweg und Sohn.

Dictionary of Hallucinations. . 2010.

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