A 58-year-old woman presents to the emergency department with acute onset of severe eye pain, blurred vision, and a fixed mid-dilated pupil. Anterior chamber is shallow, and intraocular pressure is 58 mmHg. Gonioscopy confirms angle closure. What is the drug of choice for immediate management to lower intraocular pressure?

Explanation

## Acute Angle-Closure Glaucoma: Immediate Medical Management ### Pathophysiology Acute angle closure results in sudden elevation of IOP due to pupillary block and angle obstruction. Immediate pressure reduction is critical to prevent irreversible optic nerve damage and corneal decompensation. ### Drug of Choice: Acetazolamide **Key Point:** Acetazolamide (a carbonic anhydrase inhibitor) is the drug of choice for acute angle-closure glaucoma because it: - Reduces aqueous humor production by 50% (most potent effect among all antiglaucoma drugs) - Works rapidly (oral effect in 15–30 minutes; IV in 2–5 minutes) - Lowers IOP by 30–50% acutely - Provides time for definitive therapy (laser peripheral iridotomy or surgical intervention) **High-Yield:** In acute angle closure, the goal is rapid IOP reduction to allow corneal clarity and prevent permanent vision loss. Acetazolamide is superior because it addresses the underlying mechanism (aqueous overproduction) rather than just improving outflow. ### Typical Acute Angle-Closure Treatment Protocol | Step | Intervention | Timing | |------|--------------|--------| | 1 | IV acetazolamide 500 mg or oral 500 mg | Immediate | | 2 | Topical beta-blocker (timolol) + prostaglandin analogue | Immediate (adjunctive) | | 3 | Topical apraclonidine or brimonidine | Adjunctive | | 4 | Laser peripheral iridotomy | Once IOP controlled & cornea clear | | 5 | Surgical intervention (if laser fails) | As needed | **Clinical Pearl:** Miotics (pilocarpine) are NO LONGER recommended in acute angle closure because they may worsen angle closure by causing lens-zonule relaxation and forward lens displacement in predisposed eyes. **Warning:** Acetazolamide is a sulfonamide — contraindicated in sulfa allergy. Systemic side effects (paresthesias, hypokalemia, metabolic acidosis) are acceptable in the acute setting given the vision-threatening nature of the condition. ### Why Acetazolamide Over Other Agents ```mermaid flowchart TD A[Acute Angle-Closure Glaucoma]:::outcome --> B{Mechanism of IOP elevation?}:::decision B -->|Pupillary block + angle obstruction| C[Need rapid aqueous suppression]:::action C --> D[Acetazolamide 500 mg IV/PO]:::action D --> E[IOP reduction 30-50%]:::outcome E --> F{Cornea clear?}:::decision F -->|Yes| G[Laser peripheral iridotomy]:::action F -->|No| H[Repeat acetazolamide + topical agents]:::action G --> I[Definitive treatment]:::outcome ``` **Mnemonic:** **CAI-RAPID** = Carbonic Anhydrase Inhibitor (acetazolamide) is the Rapid, Aggressive, Primary Initial Drug for acute angle closure.