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(en-top′ik) [en- + topo- + -ic] In its normal place; normally situated. SEE: ectopic.


(ĕn-tŏp′tĭk) [Gr. entos, within, + optikos, seeing] Pert. to the interior of the eye.

entoptic phenomenon

A visual phenomenon arising from within the eye, marked by the perception of floating bodies, circles of light, black spots, and transient flashes of light. It may be due to the individual's own blood cells moving through the retinal vessels, or to floaters, which are small specks of tissue floating in the vitreous fluid. SEE: Moore lightning streaks; muscae volitantes; photopsia.

Individuals may see imperfections of their own cornea, lens, and vitreous by looking at a white background through a pinhole held about 17 mm (4.3 in) from the eye. The person sees a patch of light the size of which varies with the diameter of the pupil. The abnormalities are seen as shadows or bright areas. This method can be used also to see early discrete lens opacities.

entourage effect

(on″too-rozh′) An outcome that is observed only when one agent acts in combination with several others, as when one medication is given with others.


(ĕn″tō-zō′ŏn) pl. entozoa [″ + zoon, animal] Any animal parasite living within the body of another animal.


(ĕn′trālz) The intestines of an animal.


(en-trān′) To alter the biological rhythm of an organism so that it assumes a cycle different from a 24-hr one.


(ĕn-trān′mĕnt) 1. Gaining control of a heart rhythm (esp. a tachycardic rhythm) with an external stimulus such as a cardiac pacemaker. 2. The drawing of a second fluid into a stream of gas or fluid by the Bernoulli effect.

entrance skin exposure

SEE: under exposure.


(en-trap′mĕnt) In medicine, compression, as of a peripheral nerve or vessel.


(ĕn-trō′pē-ŏn) [Gr. en, in, + trepein, to turn] An inversion or turning inward of an edge, esp. the margin of the lower eyelid. SYN: enstrophe.

cicatricial e. An inversion resulting from scar tissue on the inner surface of the lid.

spastic e. An inversion resulting from a spasm of the orbicularis oculi muscles.


(ĕn′trŏ-pē) [Gr. en, in, + trope, a turning] 1. The portion of energy within a system that cannot be used for mechanical work but is available for internal use. 2. The quantity or degree of randomness, disorder, or chaos in a system.

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