(pū′pĭl )

[L. pupilla, little doll (the reflection in the pupil)]
The contractile opening at the center of the iris of the eye. It is constricted when exposed to strong light and when the focus is on a near object; is dilated in the dark and when the focus is on a distant object. Average diameter is 4 to 5 mm. The pupils should be equal. SEE: pupilla;


PUPIL DILATION AND CONSTRICTION The upper image shows constriction; the lower, dilation.

DIFFERENTIAL DIAGNOSIS
Constriction of the pupil occurs, for example, in bright light and after exposure to drugs such as morphine, pilocarpine, physostigmine, eserine, and other miotics.

Dilation of the pupil is most often observed after treatment with mydriatic drugs (such as atropine, scopolamine, or homatropine), but may also be caused by paralysis of cranial nerve III, intracranial masses or trauma, sympathetic nervous system stimulation, and other pupillary stimuli.

Adie pupil

SEE: Adie, William John

Argyll Robertson pupil

SEE: Argyll Robertson pupil

artificial pupil

A pupil made by iridectomy when the normal pupil is occluded.

bounding pupil

Rapid dilatation of a pupil, alternating with contraction.

Bumke pupil

Dilatation of the pupil owing to psychic stimulus.

cat's-eye pupil

A pupil that is narrow and slitlike.

cornpicker's pupils

Dilated pupils found in agricultural workers who are exposed to dust from jimsonweed. The dust contains stramonium, a mydriatic.

fixed pupil

A pupil that does not react to stimuli.

Gunn pupil

SEE: Gunn, Robert Marcus

keyhole pupil

A pupil with an artificial coloboma at the pupillary margin.

luetic pupil

SEE: Argyll Robertson pupil.

Marcus Gunn pupil

SEE: Gunn, Robert Marcus

pinhole pupil

A pupil of minute size; one excessively constricted; seen after use of miotics, in opium poisoning, and in certain brain disorders.

Robertson pupil

SEE: Argyll Robertson pupil

stiff pupil

SEE: Argyll Robertson pupil.

tonic pupil

SEE: Adie pupil.

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