Mydriasis

Definition

Mydriasis is pupillary dilation (greater than 5 mm). Unilateral fixed mydriasis is an ominous neurologic sign; bilateral mydriasis may indicate drugs, brain death, or deep hypoxia.

Causes

• Anticholinergics (atropine, antihistamines, TCAs)
• Sympathomimetics (cocaine, methamphetamine)
• Head injury/increased ICP (unilateral suggests herniation)
• Brain death
• Mydriatic eye drops for exam
• Traumatic iritis

Nursing Interventions

Unilateral fixed dilated pupil = neurosurgical emergency (herniation). Assess GCS, vital signs (Cushing's triad: hypertension, bradycardia, irregular respirations), prepare for mannitol, hypertonic saline, or surgical intervention. Photophobia common during pharmacologic mydriasis (give sunglasses).

NCLEX Relevance

Unilateral blown pupil = uncal herniation (emergency).