Miosis

A pathologic or pharmacologic constriction of the pupillary aperture (diameter ≤ 2mm) due to increased sphincter pupillae tone or impaired dilator function. Possible causes are medications (opioids intoxication, cholinergic/miotic agents, nicotine, clonidine), brain injury (pontine lesion, brainstem injury, intracranial hemorrhage), Horner syndrome, eye disorder (iritis, uveitis), pesticides (organophosphate), neurosyphilis, and physiological constriction (bright light, close-up focusing, deep sleep, or normal aging).