pupil
(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
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
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
stiff pupil
tonic pupil
SEE: Adie pupil.