Acute Angle Closure Glaucoma (Adult)

1. Clinical Overview

Summary

Acute Angle Closure Glaucoma (AACG) is a sight-threatening ophthalmic emergency characterized by a sudden, severe rise in intraocular pressure (IOP) due to the physical occlusion of the trabecular meshwork by the peripheral iris. This typically occurs in anatomically predisposed eyes (short axial length, shallow anterior chamber) when the pupil is in a mid-dilated position. [1,2]

The rapid IOP spike (often > 50-70 mmHg) leads to ischaemic damage to the optic nerve, retina, and corneal endothelium. Treatment is a time-critical hierarchy: immediate medical reduction of IOP followed by definitive laser or surgical intervention. The EAGLE trial (2016) has significantly shifted the definitive paradigm toward early clear lens extraction in primary angle closure. [3,4]

Key Facts

• The "Vagal" Trap: AACG can present with profound nausea, vomiting, and abdominal pain, leading to misdiagnosis as a GI emergency.
• Pupil Block: The most common mechanism; aqueous builds behind the iris, bowing it forward (iris bombé) into the drainage angle.
• Mid-Dilated Pupil: The "at-risk" position where iris-lens contact is maximal; often triggered by dim light (e.g., cinemas) or anticholinergic drugs.
• Pilocarpine Limitation: This miotic agent will not work when IOP is > 40 mmHg because the iris sphincter is ischaemic; pressure must be lowered with systemic agents first. [5]
• Fellow Eye Risk: Without prophylactic treatment, the fellow eye has a 50% risk of an attack within 5 years.

Clinical Pearls

The "Eclipse" Pearl: Use a penlight to shine light across the cornea from the temporal side. If the nasal iris is in shadow, the anterior chamber is shallow, indicating high risk for angle closure.

The "Vomiting" Pearl: In any elderly patient with sudden-onset headache and vomiting, look at the eyes. A red, hazy eye with a fixed pupil confirms the diagnosis and saves the patient from an unnecessary CT head or abdominal workup.

The "Supine" Pearl: While waiting for the ophthalmologist, place the patient supine. Gravity allows the lens to shift posteriorly, which can partially relieve the pupillary block.

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2. Epidemiology & Risk Factors

Incidence & Distribution

• Prevalence: 1 in 1,000 Caucasians; up to 1 in 100 in East Asian populations.
• Gender: 3:1 Female-to-Male ratio (females typically have shorter axial lengths).
• Age: Peak incidence > 60 years as the lens naturally thickens and moves forward.

Risk Factors

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3. Pathophysiology

1. The Anatomical Set-up

The primary prerequisite is a shallow anterior chamber and a narrow angle. This is usually seen in hypermetropic (short) eyes or those with a thick, anteriorly displaced crystalline lens.

2. Pupillary Block

When the pupil reaches a mid-dilated position (4–6 mm), there is maximal contact between the posterior iris and the anterior lens capsule. This creates a functional valve that traps aqueous humour in the posterior chamber.

3. Iris Bombé

As aqueous continues to be produced by the ciliary body, pressure rises in the posterior chamber. This pressure bows the peripheral iris forward (iris bombé) until it makes physical contact with the trabecular meshwork (the drainage angle).

4. Pressure Crisis

Once the angle is occluded, IOP rises rapidly.

• Corneal Oedema: IOP exceeds the endothelial pump capacity, causing fluid to enter the corneal stroma ("steamy" appearance).
• Ischaemia: High pressure compresses the iris sphincter (fixed pupil) and the optic nerve head (visual loss). [7,8]

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4. Clinical Presentation

Typical Symptoms

• Severe Ocular Pain: Often described as a "boring" pain radiating to the forehead or cheek.
• Visual Changes: Sudden blurring and the classic appearance of rainbow haloes around lights (due to corneal diffraction).
• Systemic Distress: Intense nausea and vomiting (vagal stimulation).

Physical Signs

1. Acuity: Significantly reduced (often CF or HM).
2. Conjunctiva: Marked ciliary flush (violaceous redness concentrated around the limbus).
3. Cornea: Hazy or "steamy" appearance.
4. Pupil: Mid-dilated (approx 5mm), fixed (non-reactive), and often vertically oval.
5. Globe: Feels "rock-hard" on gentle digital palpation compared to the fellow eye. [9]

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5. Investigations

1. Bedside/Primary Assessment

• Visual Acuity: Mandatory baseline documentation.
• IOP Measurement (Tonometry): Goldmann or iCare. IOP usually 40–80 mmHg.
• Slit Lamp/Penlight: Assess anterior chamber depth and pupil reactivity.

2. Specialist Investigations

• Gonioscopy: The Gold Standard. Inability to visualize the pigmented trabecular meshwork confirms angle closure. (Note: difficult to perform in acute haze).
• Anterior Segment OCT: Provides a non-contact cross-sectional view of the closed angle.
• Ultrasound Biomicroscopy (UBM): Used to identify "Plateau Iris" or lens-induced mechanisms. [10]

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6. Management: The Emergency Algorithm

Management Flowchart (ASCII)

       [SUSPECTED ACUTE ANGLE CLOSURE]
                   |
       +-----------v-----------+
       |   IMMEDIATE MEDICAL   | (Supine position)
       | - IV Acetazolamide    | (500mg Stat)
       | - Topical Timolol     | (Aqueous suppressant)
       | - Topical Alpha-2 Ag. | (Apraclonidine)
       +-----------+-----------+
                   |
       +-----------v-----------+
       |   RE-ASSESS IOP (1h)  |
       +-----------+-----------+
            |              |
     (IOP less than 40 mmHg)  (IOP remains > 40)
            |              |
     +------v------+   +---v--------------+
     | PILOCARPINE |   | IV MANNITOL      |
     | (2% drops)  |   | (1g/kg 20% Sol.) |
     +------+------+   +---+--------------+
            |              |
     +------v--------------v---+
     |   DEFINITIVE THERAPY    |
     | 1. YAG Iridotomy (PI)   |
     | 2. Lens Extraction (PE) |
     | 3. Fellow Eye Proph PI  |
     +-------------------------+

1. Immediate Medical Therapy

• Acetazolamide: 500mg IV (or PO if IV unavailable). Reduces aqueous production by 50%.
• Topical Beta-blockers: Timolol 0.5% (Check for asthma/bradycardia).
• Topical Alpha-2 Agonists: Apraclonidine or Brimonidine.
• Topical Steroids: Prednisolone 1% to reduce intraocular inflammation.

2. The Pilocarpine Window

Do not give pilocarpine initially if IOP is > 40 mmHg. Once pressure drops, the iris sphincter regains its blood supply; pilocarpine then acts to pull the peripheral iris away from the angle. [11]

3. Definitive Treatment

• YAG Peripheral Iridotomy (PI): Creates a "bypass" hole in the iris to equalize pressure. Must be performed in both eyes (affected and fellow eye).
• Clear Lens Extraction: The EAGLE Trial showed that removing the lens is superior to PI for long-term IOP control in primary angle closure. [3]

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7. Complications

• Permanent Optic Atrophy: Due to ischaemic optic neuropathy during the spike.
• Peripheral Anterior Synechiae (PAS): Permanent "zippering" of the iris to the angle, leading to chronic glaucoma.
• Glaukomflecken: Grey-white subcapsular lens opacities (the "scars" of a previous attack).
• Cataract: Accelerated development following the acute ischaemic insult.
• Central Retinal Artery Occlusion (CRAO): If IOP exceeds systolic blood pressure. [12]

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8. Evidence & Landmark Trials

1. EAGLE Trial (Lancet 2016): Multi-center RCT demonstrating that early clear lens extraction is more cost-effective and provides better quality of life and IOP control than laser PI for primary angle closure. [PMID: 27707497]
2. ZAP Trial (Lancet 2019): Showed that prophylactic PI in patients with narrow angles significantly reduces the risk of future attacks, although the absolute risk reduction in asymptomatic patients is low. [PMID: 30502256]
3. Azuara-Blanco et al.: Established the role of lens extraction as the primary surgical modality in the modern era of glaucoma management. [13]

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9. Single Best Answer (SBA) Questions

Question 1

A 68-year-old female presents with a 2-hour history of severe right eye pain, nausea, and blurred vision. Her right pupil is 5mm and non-reactive. IOP is 62 mmHg. What is the most appropriate first-line systemic medication?

• A) IV Mannitol
• B) IV Acetazolamide
• C) PO Glycerol
• D) IV Methylprednisolone
• E) PO Pilocarpine
• Answer: B. IV Acetazolamide is the first-line systemic agent to rapidly suppress aqueous production. Mannitol is reserved for refractory cases or extremely high pressures.

Question 2

Why is pilocarpine 2% typically withheld in the initial management of an AACG attack where the IOP is 65 mmHg?

• A) It causes paradoxical angle closure
• B) It increases aqueous production
• C) The iris sphincter is ischaemic and non-responsive
• D) It interferes with the action of Timolol
• E) It causes systemic hypotension
• Answer: C. At IOP > 40-50 mmHg, the iris sphincter muscle is ischaemic; pilocarpine will not work until the pressure is lowered.

Question 3

An elderly patient presents with sudden-onset vomiting and severe headache. On examination, the eye is red with a "steamy" cornea. Which anatomical feature is the primary prerequisite for this condition?

• A) High axial length (Myopia)
• B) Deep anterior chamber
• C) Short axial length (Hypermetropia)
• D) Large corneal diameter
• E) Posteriorly displaced lens
• Answer: C. Hypermetropic eyes are shorter and have crowded anterior segments, predisposing them to angle closure.

Question 4

According to the findings of the EAGLE trial (2016), which treatment is recommended for long-term management of primary angle closure?

• A) Lifelong Pilocarpine drops
• B) Trabeculectomy
• C) Laser Peripheral Iridotomy (PI)
• D) Clear Lens Extraction (Phacoemulsification)
• E) Argon Laser Trabeculoplasty
• Answer: D. The EAGLE trial showed clear lens extraction was superior to PI for IOP control and quality of life.

Question 5

What is the "Eclipse Sign" used for in clinical practice?

• A) To detect retinal detachment
• B) To identify a shallow anterior chamber
• C) To measure corneal thickness
• D) To screen for cataracts
• E) To assess optic nerve cupping
• Answer: B. Shining a light temporally and seeing a nasal shadow indicates a shallow chamber.

Question 6

A 70-year-old Asian female is diagnosed with AACG in her left eye. What is the most important management step for her right (asymptomatic) eye?

• A) Discharge with no follow-up
• B) Start prophylactic Timolol
• C) Perform prophylactic YAG Peripheral Iridotomy
• D) Immediate cataract surgery
• E) Apply Pilocarpine every 2 hours
• Answer: C. The fellow eye is at high risk (~50%) and must receive prophylactic laser PI.

Question 7

Which of the following describes "Iris Bombé"?

• A) Posterior synechiae causing iris retraction
• B) Forward bowing of the peripheral iris due to posterior pressure
• C) Inflammation of the iris stroma
• D) Neovascularization of the iris surface
• E) Sectoral atrophy of the iris
• Answer: B. Aqueous buildup in the posterior chamber bows the iris forward, closing the angle.

Question 8

Which medication should be avoided in patients with a history of narrow angles?

• A) Paracetamol
• B) Amitriptyline
• C) Metformin
• D) Amlodipine
• E) Warfarin
• Answer: B. Amitriptyline (a TCA) has anticholinergic effects that can trigger mydriasis and precipitate angle closure.

Question 9

What are "Glaukomflecken"?

• A) Small retinal haemorrhages
• B) Deposits on the corneal endothelium
• C) Subcapsular lens opacities from prior IOP spikes
• D) Pigment spots on the iris
• E) Drusen near the macula
• Answer: C. They are pathognomonic evidence of a previous severe pressure crisis.

Question 10

Which cranial nerve is primarily responsible for the nausea and vomiting seen in AACG?

• A) CN II (Optic)
• B) CN III (Oculomotor)
• C) CN V (Trigeminal)
• D) CN X (Vagus)
• E) CN VII (Facial)
• Answer: D. Vagal stimulation (oculovagal reflex) is responsible for the systemic symptoms.

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12. Aqueous Mastery: The Physics of Outflow Resistance

To understand glaucoma, one must understand the "plumbing" of the eye.

A. The Poiseuille Logic

• The Flow: Aqueous humor is produced by the ciliary body, flows through the pupil, and exits via the trabecular meshwork (the drain).
• The Trap: In narrow-angle eyes, the lens is pushed forward (often due to a cataract), making the pupil a high-resistance valve. This creates a pressure difference between the back and front chambers of the eye (iris bombé), which physically pushes the iris against the drain, sealing it shut.

B. Uveoscleral Outflow

• While the trabecular meshwork is the main drain (80-90%), a small amount of fluid escapes through the eye's wall (uveoscleral route). Prostaglandin drops work by opening this "backdoor," but they are less effective in the acute phase of angle closure.

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13. Molecular Diagnostics: Genetic Risk & Trabecular Meshwork

Is glaucoma written in your DNA?

A. The PACG Genetic Map

• Recent genome-wide association studies (GWAS) have identified specific loci (e.g., EPDR1, CHCHAT, GLIS3) that are highly associated with Primary Angle Closure Glaucoma. Patients of East Asian descent have a significantly higher genetic predisposition due to shallower anterior chambers.

B. The Extracellular Matrix

• Research is focused on the trabecular meshwork's stiffness. In glaucoma, the collagen and elastic fibers in the drain become "stiffened," making it harder for fluid to pass through. New "Rho-kinase inhibitors" target this molecular stiffness to restore natural drainage.

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14. Surgical Nuances: Laser Iridotomy vs. Clear Lens Extraction

The "EAGLE" Trial has changed the standard of care.

A. Laser Peripheral Iridotomy (LPI)

• The Classic: Using a YAG laser to "punch a hole" in the iris. This acts as a pressure-relief valve, instantly equalizing pressure between the back and front chambers and allowing the iris to fall away from the drain.

B. The EAGLE Revolution

• The Change: The EAGLE trial (Lancet 2016) showed that Clear Lens Extraction (essentially doing a cataract operation early) is superior to laser for patients with angle closure and high pressure.
• The Logic: By removing the "bulky" human lens and replacing it with a thin artificial one, you permanently widen the drainage angle and often eliminate the need for eye drops entirely.

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15. Future Trends: Micro-invasive Glaucoma Surgery (MIGS)

We are moving away from "major" eye surgery toward "micro-stents."

A. The iStent and Hydrus

• The Tech: These are tiny titanium stents (smaller than a grain of rice) that are placed directly into the eye's drain during a lens operation.
• Benefit: They bypass the blocked trabecular meshwork without the complications of traditional "Tube" or "Trabeculectomy" surgery.

B. AI Imaging

• New AI-enhanced Optical Coherence Tomography (OCT) can now predict which patients are at high risk of a "pressure spike" by measuring the angle closure to within a fraction of a millimeter, allowing for preventative laser treatment before an emergency occurs.

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16. Patient Explanation

"Acute glaucoma is an eye emergency where the pressure inside your eye rises very quickly. Think of the eye like a sink: the tap is still running, but the drain is suddenly blocked. Because the fluid can't get out, the pressure builds up and starts to squeeze the 'camera wire' (optic nerve) at the back of your eye. This is why you have severe pain and blurred vision. We will use a combination of strong injections and drops to unblock the drain and lower the pressure. Once it's safe, we will use a laser to make a tiny 'safety valve' in the eye to make sure this never happens again. We will also treat your other eye as a precaution."

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17. Examination Focus: Viva & OSCE Points

The "Ocular" Viva

• The "Fixed Dilated" Pupil: Explain that the high pressure causes ischemic paralysis of the iris sphincter muscle.
• The "Cloudy" Cornea: It’s due to corneal oedema when the high pressure overcomes the corneal pump mechanism (the endothelium).
• The "Shallow" Anterior Chamber: Always check this in both eyes; it is the physical hallmark of a high-risk patient.

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18. References

1. Azuara-Blanco A, et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE). Lancet. 2016. [PMID: 27707497]
2. Prum BE, et al. Primary Angle Closure Preferred Practice Pattern. Ophthalmology. 2016. [PMID: 26581559]
3. He M, et al. Laser peripheral iridotomy for the prevention of angle closure (ZAP trial). Lancet. 2019. [PMID: 30502256]
4. Wright WV, et al. Acute angle-closure glaucoma: An update on management. Postgrad Med J. 2015.
5. AAO. Glaucoma (Basic and Clinical Science Course). 2023.

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Last Updated: 2026-01-05 | MedVellum Editorial Team