Autonomic Pharmacology USMLE Step 1 Practice Question
A 65-year-old woman with narrow-angle glaucoma presents to ophthalmology for routine examination. She is accidentally instilled with tropicamide 1% eye drops. Within 30 minutes, she develops severe eye pain, blurred vision, and photophobia. Vital signs: BP 158/92 mmHg, HR 102/min, RR 18/min. Intraocular pressure is measured at 55 mmHg in the affected eye. Slit-lamp examination reveals a mid-dilated, fixed pupil at approximately 6 mm. Gonioscopy confirms angle closure. She denies nausea or vomiting. Her baseline intraocular pressure was 18 mmHg at her last visit. Which mechanism explains this acute crisis?
Answer choices
- ANicotinic agonism causing pupillary constriction paradoxically
- BDirect inhibition of carbonic anhydrase in the ciliary body
- CMuscarinic antagonism causing mydriasis and angle closureCorrect answer
- DBeta-1 blockade reducing aqueous humor outflow
- EAlpha-adrenergic stimulation causing iris ischemia
- FInhibition of prostaglandin F receptor signaling leading to decreased uveoscleral outflow
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