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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Acute angle closure = sudden obstruction of aqueous outflow with rapidly elevated IOP, often >40-60 mmHg
- Classic triad: severe painful red eye + halos/blurred vision + nausea/vomiting
- Exam: cloudy cornea, conjunctival injection, shallow anterior chamber, fixed mid-dilated pupil, hard globe
- Immediate management: urgent ophthalmology, IOP-lowering drops + acetazolamide, then laser peripheral iridotomy
- Avoid dilating agents and anticholinergic/sympathomimetic triggers in susceptible narrow-angle patients
Overview
Acute angle-closure glaucoma is an ophthalmic emergency caused by abrupt closure of the anterior chamber angle, most commonly through pupillary block. Aqueous humor cannot drain through the trabecular meshwork, causing rapid elevation of intraocular pressure and ischemic injury to the optic nerve and iris. It must be distinguished from conjunctivitis, uveitis, corneal abrasion, keratitis, and migraine because delayed treatment can cause irreversible vision loss within hours.
Epidemiology
Angle-closure disease is less common than open-angle glaucoma in the United States but carries a high risk of acute morbidity. Risk factors include older age, female sex, Asian or Inuit ancestry, hyperopia, shallow anterior chamber, short axial length, thick or anteriorly positioned lens, family history, and medications causing pupillary dilation. Attacks may occur in dim light, after pharmacologic dilation, or after anticholinergic/sympathomimetic exposure.
Clinical Features
Symptoms
Sudden severe unilateral eye pain and headache
Blurred vision with halos around lights from corneal edema
Nausea and vomiting — frequently mistaken for gastrointestinal or neurologic disease
Photophobia and tearing
Precipitating history: dark room, movie theater, anticholinergic medication, decongestant, or recent eye dilation
Signs
Markedly elevated IOP, often 40-80 mmHg
Conjunctival injection with ciliary flush
Cloudy or steamy cornea from corneal edema
Fixed mid-dilated pupil with sluggish or absent light response
Shallow anterior chamber and hard globe on gentle palpation
Reduced visual acuity
Investigations
First-line
TonometryShows markedly elevated IOP; do not delay treatment if classic presentation and ophthalmology is en route
Slit-lamp examinationCorneal edema, shallow anterior chamber, iris bombe, and conjunctival/ciliary injection
Visual acuity and pupillary examDocument baseline acuity and fixed mid-dilated pupil; assess for relative afferent pupillary defect if advanced damage
Second-line
GonioscopyConfirms angle closure but is often performed by ophthalmology after initial pressure reduction
Anterior segment OCT or ultrasound biomicroscopyMay define angle anatomy, plateau iris, lens vault, or secondary mechanisms
Specialist
Contralateral eye evaluationFellow eye commonly has anatomically narrow angle and usually requires prophylactic laser peripheral iridotomy
1
Immediate emergency treatment
- Urgent ophthalmology consultation — do not discharge with presumed conjunctivitis or migraine
- Topical beta-blocker: timolol unless contraindicated
- Topical alpha-2 agonist: apraclonidine or brimonidine
- Topical carbonic anhydrase inhibitor: dorzolamide or brinzolamide
- Systemic acetazolamide 500 mg PO/IV if no sulfonamide allergy, severe renal disease, or significant contraindication
- Analgesia and antiemetics; avoid mydriatic or anticholinergic medications
2
When IOP begins to fall
- Pilocarpine may be added once IOP is lower; it is often ineffective initially when the ischemic iris sphincter cannot constrict
- Hyperosmotic therapy such as IV mannitol or oral glycerol may be used for refractory severe IOP elevation
- Monitor systemic status carefully in patients with heart failure, renal disease, or diabetes when using hyperosmotics
3
Definitive treatment
- Laser peripheral iridotomy (LPI) creates an alternative pathway for aqueous flow and relieves pupillary block
- Treat the fellow eye prophylactically when anatomically narrow or at risk
- Lens extraction may be considered in selected patients with cataract or lens-driven angle closure
4
Prevention
- Identify narrow-angle patients before pharmacologic dilation when feasible
- Review medication triggers: antihistamines, tricyclic antidepressants, antipsychotics, topiramate, decongestants, and anticholinergics
- Educate patients to seek emergency care for painful red eye with halos, vomiting, or sudden visual blurring
Complications
- Permanent optic nerve damage: Irreversible vision loss can occur rapidly if IOP remains high
- Peripheral anterior synechiae: Chronic angle closure after an acute attack
- Corneal edema/decompensation: From sustained very high IOP
- Recurrent angle closure: Especially if LPI is delayed or the mechanism is non-pupillary block
- Fellow-eye attack: High risk without prophylactic evaluation and treatment
USMLE Step 2 CK Exam Tips
- 1Painful red eye + halos + vomiting + fixed mid-dilated pupil = acute angle-closure glaucoma
- 2Next best step: urgent ophthalmology and immediate IOP-lowering therapy, not outpatient follow-up
- 3Definitive treatment is laser peripheral iridotomy, but acute medications are given first to lower IOP
- 4Pilocarpine is not the first effective drug when IOP is extremely high because the iris sphincter is ischemic
- 5Differentiate from conjunctivitis: conjunctivitis causes discharge/itching but not severe pain, vomiting, cloudy cornea, or fixed pupil
- 6Anticholinergics and sympathomimetics can precipitate attacks in narrow-angle eyes
- 7Hyperopia and shallow anterior chamber are high-yield risk factors
- 8Open-angle glaucoma is painless and chronic; angle closure is painful and acute
practicetest your knowledge on acute angle-closure glaucomaApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ophthalmology and beyond.
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