Miosis vs mydriasis

Quick Pathways

• Miosis (Constriction): Parasympathetic $\to$ CN III $\to$ Ciliary ganglion $\to$ Sphincter pupillae.
• Mydriasis (Dilation): Sympathetic $\to$ Hypothalamus $\to$ C8–T2 $\to$ Superior cervical ganglion $\to$ Dilator pupillae.

Miosis (Pinpoint / Constricted)

• Opioid OD: Pinpoint pupils + $\downarrow$ RR ($\text{RR}<8$) + CNS depression $\to$ Tx: IV Naloxone.
• Cholinergic Tox (Organophosphates): Pinpoint + DUMBBELLS (Diarrhea, Urination, Miosis, Bradycardia/Bronchorrhea, Emesis, Lacrimation, Salivation) $\to$ Tx: Atropine + Pralidoxime (2-PAM).
• Pontine Hemorrhage: Pinpoint (reactive) + Coma + Hyperpyrexia + Quadriplegia.
• Horner Syndrome: Unilateral Miosis + Ptosis + Anhidrosis (Apical Pancoast tumor, Carotid dissection).
• Argyll Robertson: Small, irregular; accommodates but does NOT react to light (Neurosyphilis).

Mydriasis (Dilated)

• Sympathomimetics (Cocaine, Amphetamines): Dilated + Tachycardia + HTN + Diaphoretic/Wet skin $\to$ Tx: Benzodiazepines (avoid pure $\beta$-blockers).
• Anticholinergics (TCAs, Diphenhydramine, Atropine): Dilated + Delirium + Anhidrotic/Dry skin + Urinary retention + Ileus.
• Serotonin Syndrome: Dilated + Hyperthermia + Clonus / Hyperreflexia $\to$ Tx: Cyproheptadine.
• Opioid Withdrawal: Dilated + Piloerection + Yawning + Rhinorrhea + Diarrhea.
• Compressive CN III Palsy (PCom Aneurysm, Uncal Herniation): Fixed, blown pupil $\pm$ “Down-and-out” eye $\to$ Dx: Emergent CTA/MRA.
• Acute Angle-Closure Glaucoma: Mid-dilated fixed pupil + Hazy cornea + Severe ocular pain/Headache + $\uparrow$ IOP ($>30\text{ mmHg}$).