Acute Angle-Closure Glaucoma — Emergent IOP Reduction

Key Points

• Acute angle closure is vision-threatening and requires same-day emergency ophthalmology care.
• Measure IOP in a painful red eye with headache, nausea, or visual halos.
• Use medical therapy first to lower IOP and clear corneal edema.
• Aqueous suppressants and systemic acetazolamide are standard initial therapies when not contraindicated.
• Pilocarpine may be ineffective at very high IOP and is often given after pressure begins to fall.
• Laser peripheral iridotomy is definitive for pupillary-block angle closure.
• The fellow eye usually requires preventive evaluation and treatment.
• Secondary angle closure should be recognized because iridotomy alone may not solve the cause.

Algorithm

1. Check visual acuity, pupils, cornea, anterior chamber, and intraocular pressure immediately.
2. Call ophthalmology urgently and begin topical aqueous suppressants plus systemic acetazolamide when safe.
3. Reassess IOP after initial therapy and add pilocarpine when pressure has begun to decrease and pupillary block is the mechanism.
4. Use hyperosmotic therapy for severe refractory IOP according to cardiac and renal status.
5. Treat inflammation and nausea while avoiding mydriatic medications.
6. Perform laser peripheral iridotomy as soon as corneal clarity permits.
7. Evaluate and usually treat the fellow narrow-angle eye prophylactically.
8. Plan lens or plateau-iris management when anatomy requires additional definitive therapy.

Clinical Synopsis & Reasoning

Primary acute angle closure usually occurs in anatomically narrow anterior chambers when pupillary block causes the peripheral iris to obstruct the trabecular meshwork. Risk rises with age, hyperopia, female sex, Asian or Inuit ancestry, and medications that dilate the pupil or alter lens-iris relationships. Secondary angle closure can occur from uveitis, neovascular disease, lens disorders, medications, or posterior-segment pathology and may require a different definitive treatment.

Symptoms are typically unilateral severe eye pain, red eye, decreased vision, halos around lights, headache, nausea, and vomiting. Examination can show cloudy cornea, shallow anterior chamber, fixed or sluggish mid-dilated pupil, and markedly elevated IOP. Because nausea and headache can dominate, patients are sometimes misdiagnosed with migraine or gastroenteritis. Measure visual acuity and IOP promptly in any older patient with severe headache plus red eye or vision change.

Differential diagnoses include anterior uveitis, keratitis, scleritis, endophthalmitis, conjunctivitis, and headache disorders. Fluorescein staining helps identify corneal epithelial disease. Slit-lamp examination can assess chamber depth, cells/flare, and corneal edema. Gonioscopy confirms angle closure but is usually performed by ophthalmology once the acute state is controlled.

Treatment Strategy & Disposition

The 2025 AAO Preferred Practice Pattern recommends medical treatment or other immediate interventions to lower IOP and clear corneal edema, followed by laser peripheral iridotomy for pupillary-block disease. Start topical timolol unless contraindicated, an alpha-2 agonist such as brimonidine or apraclonidine, and a topical carbonic anhydrase inhibitor. Give acetazolamide systemically when renal function, sulfonamide reaction history, electrolytes, and other contraindications permit. Recheck IOP and symptoms frequently.

Pilocarpine is often delayed until IOP begins to fall because a severely ischemic iris sphincter may not respond when pressure is extremely high. Hyperosmotic therapy such as IV mannitol can be used for persistently severe IOP or visual threat, with caution in heart failure or renal disease. Topical corticosteroid can reduce inflammatory response under ophthalmology direction. Avoid mydriatic and anticholinergic drugs that may worsen pupillary block.

Definitive laser peripheral iridotomy relieves pupillary block and should be performed as soon as practical after the cornea clears. The fellow eye is at substantial risk and typically also needs prophylactic iridotomy when anatomically narrow. Lens extraction can provide definitive anatomic treatment in selected patients and may be recommended after acute stabilization. Persistent closure despite a patent iridotomy suggests plateau iris or another secondary mechanism requiring additional ophthalmic treatment.

Epidemiology / Risk Factors

• Primary angle-closure disease is more common in older adults and certain anatomic and ancestry groups.
• Hyperopia and shallow anterior chambers increase risk.
• Medication-triggered pupil dilation can precipitate an attack in anatomically susceptible eyes.
• The fellow eye is often anatomically narrow and at meaningful future risk.
• Early treatment prevents irreversible optic-nerve injury.

Investigations

Medication Sequence (Example)

Pharmacology

Prognosis / Complications

• Vision can recover well when IOP is lowered rapidly before significant optic-nerve injury occurs.
• Delayed treatment can produce permanent visual-field loss or blindness.
• Repeated attacks or chronic synechial closure can lead to chronic angle-closure glaucoma.
• Definitive iridotomy substantially reduces recurrent pupillary-block attacks.
• Some patients still need chronic pressure-lowering treatment or lens extraction after iridotomy.

Patient Education / Counseling

• Seek emergency care for recurrent severe eye pain, red eye, halos, sudden blurred vision, nausea, or headache.
• Use prescribed eye drops exactly as directed and do not stop them because pain improves.
• Tell clinicians and pharmacists about narrow-angle disease before receiving medications that can dilate the pupil.
• Attend ophthalmology follow-up for gonioscopy, optic-nerve assessment, and treatment of the fellow eye.
• Understand that laser iridotomy prevents pupillary block but may not eliminate all glaucoma risk.
• Report any sudden vision change in either eye immediately.

Notes

AAO 2025 guidance emphasizes medical IOP lowering first to relieve pain and clear corneal edema, followed by definitive laser peripheral iridotomy for pupillary-block disease.

The emergency clinician's role is rapid recognition, immediate pressure reduction, medication safety, and ophthalmology activation. Definitive anatomic treatment prevents recurrence and protects the fellow eye.

References

1. AAO Primary Angle-Closure Disease Preferred Practice Pattern 2025 — Link
2. AAO Glaucoma Summary Benchmarks 2025 — Link