asthenopic scotoma
   The term asthenopic scotoma comes from the Greek words a (not), sthenos (force), opsis (seeing), and skotos (darkness). In biomedicine the term asthenopia is used to denote ocular fatigue or discomfort due to strain. The introduction of the term is attributed to the Scottish ophthalmologist William Mackenzie (1791-1868). The term asthenopic scotoma is used to denote a " scotoma (i.e. an area of loss of vision) characterized by the disappearance of all or part of a visual stimulus, usually occurring after a latency period. Common examples of an asthenopic scotoma are the disappearance of letters while one is reading a book and the disappearance of visually perceived objects, leaving behind a grey mist. Such instances tend to have a duration of several seconds, after which time the objects at hand are suddenly perceived again in a normal manner. Etiologically, asthenopic scotoma is associated primarily with " migraine aura.
   Mackenzie, W. (1841). The physiology of vision. London: Longman, Orme, Brown, Green & Longmans.
   Willanger, R., Klee, A. (1966). Metamorphop-sia and other visual disturbances with latency occurring in patients with diffuse cerebral lesions. Acta Neurologica Scandinavica, 42, 118.
   Klee, A., Willanger, R. (1966). Disturbances of visual perception in migraine. Acta Neurolog-ica Scandinavica, 42, 400-414.

Dictionary of Hallucinations. . 2010.

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