Ophthalmologic emergency — sudden IOP elevation from blocked aqueous outflow; vision loss if not treated within hours.
Also known as: acute angle-closure glaucoma, AACG, angle closure crisis, pupillary block glaucoma
Overview
Sudden, marked rise in intraocular pressure (IOP) caused by mechanical obstruction of aqueous humor outflow at the trabecular meshwork from apposition of the iris against the angle. Most often results from pupillary block in an anatomically predisposed eye with a shallow anterior chamber.
Epidemiology
Uncommon: annual incidence about 2-4 per 100,000 in European populations and about 12 per 100,000 adults aged 30 and older in Singapore. Higher prevalence in Asians (especially East Asians) and Inuit; female:male approximately 3:1; mean age 55-65. Hyperopes have shallower anterior chambers and higher risk.
Try two board-style Acute Angle-Closure Glaucoma questions
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Question 1NeurologyMedium
A 29-year-old woman with migraine without aura started topiramate for prophylaxis 11 days ago and increased the dose 3 days ago. She now has 1 day of bilateral eye pain, frontal headache, and blurred distance vision, although near print has become easier to read than before. Both eyes are diffusely injected with hazy corneas and mid-dilated, sluggish pupils. Visual acuity is 20/80 in each eye, and intraocular pressure is 44 mm Hg on the right and 41 mm Hg on the left. Refraction documents a new 3-diopter myopic shift in both eyes, and the anterior chambers are shallow bilaterally. Which of the following is the most appropriate next step in management?
AStop topiramate and recheck vision and intraocular pressure in 1 week
BStop topiramate and start pressure-lowering drops and cycloplegic atropine
CContinue topiramate and start hourly topical pilocarpine drops in both eyes
DReduce the topiramate dose and add a pressure-lowering beta-blocker drop
EStop topiramate and arrange urgent bilateral laser peripheral iridotomies
Reveal answer & full explanation
Correct answer: B — Stop topiramate and start pressure-lowering drops and cycloplegic atropine
AStop topiramate and recheck vision and intraocular pressure in 1 week
BStop topiramate and start pressure-lowering drops and cycloplegic atropine✓
CContinue topiramate and start hourly topical pilocarpine drops in both eyes
DReduce the topiramate dose and add a pressure-lowering beta-blocker drop
EStop topiramate and arrange urgent bilateral laser peripheral iridotomies
Why Stop topiramate and start pressure-lowering drops and cycloplegic atropine is correct
Topiramate, a sulfamate-substituted monosaccharide, triggers an idiosyncratic ciliochoroidal effusion within days to about 2 weeks of starting or escalating the drug; the swollen ciliary body rotates forward, slackens the zonules, and pushes the lens-iris diaphragm anteriorly so that both angles close at once
Forward movement and thickening of the lens also increase the eye's refractive power, producing the acute myopic shift that blurs distance vision while near print sharpens - the fingerprint that separates this reaction from primary angle closure
The reaction is idiosyncratic rather than dose-proportional, so it can follow a first dose or a dose increase, and it will not settle while the drug is on board; stopping topiramate is the definitive step but not a sufficient one, because the shut angle and the pressure still have to be treated today
A pressure in the 40s injures the optic nerve within hours, so the same visit lowers it with aqueous suppressants - a topical beta-blocker, a topical alpha-2 agonist, and a topical or systemic carbonic anhydrase inhibitor - reserving a hyperosmotic agent such as mannitol, which works by a different route and pulls water osmotically out of the vitreous, for a pressure that does not fall
Cycloplegia with atropine is the half aimed at the mechanism: it rotates the ciliary body back, tightens the zonules, and lets the lens-iris diaphragm fall back so the angle reopens
Bilateral simultaneous closure in a 29-year-old is the tell: primary angle closure is typically a unilateral event in older hyperopes, so a drug started 11 days ago owns this presentation until proven otherwise
Why the others are wrong
Stop topiramate and arrange urgent bilateral laser peripheral iridotomies - withdrawal is right and the urgency is right, but the laser is the wrong second half: an iridotomy helps only when aqueous is trapped behind the iris by pupillary block, and there is no pupillary block here - a swollen ciliary body has pushed the whole lens-iris diaphragm forward, so the angle stays shut after the openings are made (the trap is running the primary angle-closure algorithm on a secondary mechanism)
Continue topiramate and start hourly topical pilocarpine drops in both eyes - both halves are wrong: the effusion will not settle while the drug is on board, and pilocarpine is the reflex miotic from primary angle closure that contracts the ciliary muscle, slackens the zonules, and lets the lens sit still further forward, which can deepen this closure. Cycloplegia, not miosis, reverses the mechanism (the trap is reaching for the drug that works when the problem is pupillary block)
Reduce the topiramate dose and add a pressure-lowering beta-blocker drop - a beta-blocker is a legitimate part of pressure lowering, but the reaction is idiosyncratic rather than dose-proportional, so a lower dose keeps the effusion going, and aqueous suppression without cycloplegia leaves the angle mechanically shut (the trap is treating an idiosyncratic reaction as though it were a dose-related side effect)
Stop topiramate and recheck vision and intraocular pressure in 1 week - withdrawal is the definitive step and most cases do settle within 1 to 2 weeks of stopping, which is why watchful waiting baits, but a pressure in the 40s with corneal edema and 20/80 acuity can injure the optic nerve within hours, so the pressure and the shut angle are treated today with aqueous suppressants and cycloplegia rather than left to the drug washout (the trap is treating withdrawal as sufficient on its own)
Additional high-yield points
Reassurance is the other tempting error: paresthesias, taste change, cognitive slowing, and painless blurring are the benign self-limited effects of topiramate, but acuity of 20/80 with corneal edema and a pressure above 40 mm Hg is a sight-threatening emergency that cannot be watched for a day
The same ciliochoroidal effusion syndrome is reported with other sulfonamide-derived drugs - hydrochlorothiazide, sulfamethoxazole, and zonisamide - so ask about every new prescription in any bilateral acute angle closure
Anticholinergic and sympathomimetic mydriasis can also precipitate angle closure, but that mechanism IS pupillary block in an anatomically narrow eye, and those eyes do respond to laser peripheral iridotomy
In primary acute angle closure the sequence is medical pressure lowering first, then definitive laser peripheral iridotomy of the affected eye plus a prophylactic iridotomy of the fellow eye
Most drug-induced cases settle within 1 to 2 weeks of stopping the drug; do not rechallenge, and switch prophylaxis to another class such as propranolol, candesartan, or a CGRP monoclonal antibody - zonisamide is a sulfonamide like topiramate, and amitriptyline is a poor choice after an angle-closure episode because its anticholinergic effect is itself a recognized precipitant
Topiramate's other counseling points for a young woman: nephrolithiasis, metabolic acidosis, weight loss, oligohidrosis with hyperthermia, and teratogenicity (oral clefts), so pregnancy status and contraception are addressed before it is started
Question 2EENTMedium
A 63-year-old hyperopic woman presents to the emergency department with 3 hours of severe right eye pain, blurred vision with halos around lights, and nausea with vomiting that began while she was watching a movie. On exam the right conjunctiva is injected, the cornea appears cloudy and steamy, and the pupil is mid-dilated at 5 mm and poorly reactive. The globe feels firm to palpation. Which of the following is the most appropriate next diagnostic test?
ATonometry to measure IOP
BFluorescein corneal stain
CGonioscopy of the angle
DDilated funduscopic exam
ENoncontrast CT of the head
Reveal answer & full explanation
Correct answer: A — Tonometry to measure IOP
ATonometry to measure IOP✓
BFluorescein corneal stain
CGonioscopy of the angle
DDilated funduscopic exam
ENoncontrast CT of the head
Why Tonometry to measure IOP is correct
The vignette is classic acute angle-closure glaucoma: a hyperopic older woman with sudden unilateral pain, halos, nausea/vomiting, a steamy cornea, a mid-dilated fixed pupil, and a rock-hard globe after dim-light (movie theater) exposure.
Measuring intraocular pressure with a Goldmann applanation tonometer or Tono-Pen is the primary objective diagnostic step; pressures are typically 40-80 mmHg (normal 10-21) and confirm the diagnosis while treatment is initiated.
Why the others are wrong
Gonioscopy of the angle — directly visualizes the closed angle and is the eventual confirmatory test, but it is deferred until IOP is medically controlled and the cloudy, edematous cornea clears, so it is not the next step.
Fluorescein corneal stain — detects corneal abrasion or keratitis (foreign-body sensation, fluorescein uptake); it would be negative here and does not assess the elevated pressure driving this presentation.
Dilated funduscopic exam — pharmacologic mydriasis is contraindicated in suspected angle closure because dilating the pupil can precipitate or worsen pupillary block.
Noncontrast CT of the head — severe pain with nausea and vomiting can suggest an intracranial process such as subarachnoid hemorrhage, a classic reason angle closure is missed, but the injected eye, steamy cornea, mid-dilated poorly reactive pupil, and firm globe localize the problem to the eye; head imaging only delays the bedside pressure measurement that confirms the diagnosis.
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Hyperopia with a shallow anterior chamber and narrow angle — the anatomic prerequisite and strongest risk factor (dim light and mydriatic drugs are only triggers)
Pharmacologic mydriasis (anticholinergics, sympathomimetics, antihistamines, tricyclics); separately, topiramate and other sulfonamide drugs close the angle by ciliary body swelling, not pupillary block
Dim light (movie theater, evening) — pupil mid-dilated, maximizes iris-lens contact and iris bunching at angle
Pathophysiology
Pupillary block: in eyes with shallow anterior chamber and crowded angle, the iris contacts the anterior lens surface, blocking aqueous flow from posterior to anterior chamber. Aqueous accumulates posteriorly, bowing the iris forward (iris bombe) and pressing the peripheral iris against the trabecular meshwork. IOP rapidly rises (often >40-60 mmHg), causing optic nerve ischemia, corneal edema, and pain. Plateau iris (less common): anterior insertion of the ciliary body causes peripheral iris to crowd the angle without pupillary block.
Clinical presentation
Symptoms
Sudden severe unilateral eye pain and headache
Blurred vision and halos around lights (corneal edema)
Nausea and vomiting (vagal response) — often misdiagnosed as abdominal/GI process
Photophobia
Symptoms may follow dim-light exposure, anticholinergic use, or emotional stress
Signs / physical exam
Markedly elevated IOP — typically 40-80 mmHg (normal 10-21)
Systemic carbonic anhydrase inhibitor — acetazolamide 500 mg IV or PO (avoid in sulfa allergy with caution, sickle cell)
Topical pilocarpine 1-2% (may repeat every 15 min × 2) as part of the initial combined regimen in primary angle closure — often ineffective until IOP falls below ~40-50 mmHg because the iris sphincter is ischemic, so never rely on it alone; avoid in topiramate/sulfonamide-induced angle closure
Hyperosmotic agent — oral glycerol 1-2 g/kg or IV mannitol 1-2 g/kg — if IOP not responding (avoid in heart failure)
Topical corticosteroid (prednisolone acetate 1%) every 15-30 min to reduce inflammation
Second-line / adjunct
DEFINITIVE — laser peripheral iridotomy (LPI) by ophthalmology once cornea clears, usually within 24-48 hours; LPI also performed on fellow eye prophylactically (high risk)
Cataract extraction (lens-induced) increasingly favored as definitive therapy in many cases
Surgical iridectomy if LPI not feasible
Trabeculectomy or tube shunt if chronic angle closure with persistent IOP elevation
Argon laser peripheral iridoplasty in plateau iris configuration
Complications
Permanent optic nerve damage and visual field loss within hours
Central retinal artery or vein occlusion from sustained high IOP
Glaukomflecken (anterior subcapsular lens opacities from ischemia)
Iris atrophy with sphincter paralysis (fixed dilated pupil)
Chronic angle-closure glaucoma with peripheral anterior synechiae
Bilateral disease — fellow eye is at high risk; prophylactic LPI is standard
PANCE pearls
Acute angle-closure glaucoma can present with nausea and headache and be misdiagnosed as GI illness or migraine — always check the eye and the pupil.
Pilocarpine does not work when IOP is very high because the ischemic iris sphincter cannot constrict — give it together with aqueous suppressants (± hyperosmotics) and repeat it as the pressure falls; never rely on it alone.
Topiramate and other sulfonamide drugs can cause idiosyncratic bilateral angle closure from ciliochoroidal effusion (ciliary body swelling), usually within 2 weeks of starting or raising the dose and with an acute myopic shift — stop the drug, lower IOP with aqueous suppressants, and give a cycloplegic (atropine) to rotate the ciliary body back; avoid pilocarpine, and iridotomy is NOT effective.
After medical control, definitive treatment is laser peripheral iridotomy (or lens extraction) — and the fellow eye almost always needs prophylactic iridotomy.
References
AAO 2020 — American Academy of Ophthalmology. Primary Angle Closure Disease Preferred Practice Pattern. Ophthalmology 2021;128(1):P30-P70
EAGLE Trial — Azuara-Blanco A et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomised controlled trial. Lancet 2016;388(10052):1389-1397
ZAP Trial — He M et al. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet 2019;393(10181):1609-1618
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