Entopic

Entopic is an adjective with at least two meanings. First, it can mean "in the usual place" to refer to medical or anatomical objects. It is in distinction to ectopic, which means "not in the usual place" (such as an ectopic pregnancy). In an Ovid search of Index Medicus and PsychINFO conducted on 2005 April 20, there were 36 instances of entopic, of which 14 were in its medical sense.

Second, it can mean entoptic, that is "visible because of something within the eye" or "visible without an external stimulus". In the same Ovid search, there were 22 instances of this visual meaning of entopic, mainly from Psychology journals. In four cases, both entopic and entoptic were used in the same reference, suggesting that entopic is a typographical error that has taken on a life of its own. Manor (1990) supported this view. In a similar Ovid search, there were 281 instances of entoptic, all in its (correct) visual meaning. Google searches on the same date for "entoptic" (4680), "entoptic phenomenon" (3240), "entopic -ectopic -pregnancy -anatomy" (3630), and "entopic phenomenon" (455), support the view that entopic is a widespread typographical error.

Reference

Manor, R. S. (1990). Erratum: Entoptic [corrected] phenomena in pregeniculate and postgeniculate hemianopsia with splitting of macula by perimetry. American Journal of Ophthalmology, 109, 375.