mydriasis (redirected from Pupil dilation)

mydriasis /my·dri·a·sis/ (mĭ-dri´ah-sis) [Gr.] dilatation of the pupil.

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my·dri·a·sis (m-dr-ss)

n.

Prolonged abnormal dilation of the pupil of the eye induced by a drug or caused by disease.

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mydriasis

[midrī′əsis]

Etymology: Gk, mydros, hot mass

1 dilation of the pupil of the eye caused by contraction of the dilator muscle of the iris, a muscular sheath that radiates outward like the spokes of a wheel from the center of the iris around the pupil. With a decrease in light or the pharmacologic action of certain drugs, the dilator acts to pull the iris outward, enlarging the pupil.

2 an abnormal condition characterized by contraction of the dilator muscle, resulting in widely dilated pupils. See also alternating mydriasis. Compare miosis. mydriatic, adj.

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mydriasis [mĭ-dri´ah-sis]

great dilatation of the pupil.

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mydriasis

(midrī´sis),
n an abnormal condition of the eye characterized by contraction of the dilator muscle, resulting in widely dilated pupils.

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mydriasis

gross dilatation of the pupil. Common causes in animals are atropine poisoning, hypocalcemia and tiger snake envenomation. Permanent dilatation may be due to damage to the retina, as in toxoplasmosis, or to the optic nerve, as in avitaminosis A.

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mydriasis

1. Dilatation of the pupil. 2. The condition of an eye having an abnormally large pupil diameter (5 mm in daylight). The condition may be due to a paralysis of the sphincter pupillae muscle, to an irritation of the sympathetic pathway, to a drug (e.g. atropine, homatropine), or to adaptation to darkness. See miosis; dilator pupillae muscle; mydriatic; pupil.