Mydriasis

//mɪˈdɹaɪ ə sɪs// noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    The condition of having abnormally large and dilated pupils due to illness or narcotics, particularly stimulants such as methamphetamine, cocaine, etc. countable, uncountable
  2. 2
    reflex pupillary dilation as a muscle pulls the iris outward; occurs in response to a decrease in light or certain drugs wordnet

Antonyms

All antonyms

Example

More examples

"Technically, drugs that cause miosis can relieve the PNS effects of those causing mydriasis since sympathetic and parasympathetic stimulation tend to negate each others' effects."

Etymology

From Latin mydriasis, from Ancient Greek μυδρίᾱσις (mudríāsis, “undue enlargement of the pupil”), from μύδρος (múdros, “mass of red hot material in a forge”), possibly because the pupil is particularly bright or sparkling when dilated, or because of the red eye effect when exposed to a flash of light.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.