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 the opposite of ectopic, which means "not in the usual place" (such as an ectopic pregnancy). In an Ovid search of Index Medicus and PsycINFO conducted on April 20 2005 , there were thirty six instances of entopic, of which fourteen were in its medical sense.

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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 twenty two 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 become more prevalent. 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.

This view can be supported etymologically: the words entopic and entoptic both have Greek roots; en means "in"; topos means "place", ento or ent- means "within" and optic refers to "sight" or "eye".

Entopic graphomania is a surrealist method in which dots are made at the sites of impurities in a blank sheet of paper, and lines are then made between the dots.

References

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.