Overview
Acute Angle-Closure Glaucoma
1. Clinical Overview
Summary
Acute angle-closure glaucoma (AACG) is an ophthalmic emergency caused by sudden obstruction of aqueous outflow due to iridotrabecular apposition. This causes rapid rise in intraocular pressure (IOP), typically over 40 mmHg. Classic presentation is severe eye pain, red eye, fixed mid-dilated pupil, reduced vision, and haloes around lights. Nausea and vomiting are common. Untreated, it causes irreversible optic nerve damage within hours. Treatment is urgent IOP reduction and definitive laser peripheral iridotomy.
Key Facts
- Mechanism: Iris blocks trabecular meshwork → aqueous can't drain → IOP rises rapidly
- IOP: Often over 40 mmHg (normal 10-21)
- Presentation: Severe eye pain, red eye, mid-dilated fixed pupil, reduced vision, haloes
- Emergency: Can cause permanent blindness within hours
- Treatment: Medical IOP reduction → laser peripheral iridotomy (definitive)
Clinical Pearls
Mid-dilated FIXED pupil = AACG until proven otherwise
Patient may present to A&E with "headache and vomiting" — always check the eyes
Precipitants: Dim lighting, mydriatic drugs, anticholinergics
Why This Matters Clinically
AACG is a true ophthalmic emergency. Delayed treatment leads to permanent vision loss. Non-ophthalmologists must recognise it to ensure urgent referral.
2. Epidemiology
Incidence
- 0.1-0.2% lifetime risk
- More common in Asians (shallower anterior chamber)
- Peak age: 55-70 years
Demographics
- Female predominance (3:1)
- Hyperopia (long-sighted) — shallow anterior chamber
- Asian ethnicity
Risk Factors
| Factor | Notes |
|---|---|
| Hyperopia | Shallow anterior chamber |
| Asian ethnicity | Anatomical predisposition |
| Female sex | |
| Family history | |
| Increasing age | Lens thickens |
| Dim lighting | Pupil dilates |
| Mydriatic drugs | Tropicamide, atropine |
| Anticholinergics | Many medications |
3. Pathophysiology
Mechanism
- Anatomically narrow angle (shallow anterior chamber)
- Pupil dilates (dim light, drugs)
- Iris bows forward (pupil block)
- Iris occludes trabecular meshwork
- Aqueous humour cannot drain
- Rapid IOP rise
Why Damage Occurs
- High IOP compresses optic nerve fibres
- Ischaemia to optic nerve
- Permanent ganglion cell death within hours
Pupil Block
- Most common mechanism
- Aqueous trapped behind iris → iris bows forward
- Relieved by iridotomy
4. Clinical Presentation
Symptoms
Signs
Red Flags
| Finding | Significance |
|---|---|
| Fixed mid-dilated pupil | Classic AACG |
| Rock-hard eye | Very high IOP |
| Cloudy cornea | Corneal oedema from high IOP |
| Profound vision loss | Emergency |
Severe eye pain — unilateral
Common presentation.
Reduced vision — often profound
Common presentation.
Haloes around lights — corneal oedema
Common presentation.
Headache — may be frontal or periorbital
Common presentation.
Nausea and vomiting — vagal response to pain
Common presentation.
5. Clinical Examination
Visual Acuity
- Often severely reduced (counting fingers or worse)
Pupil
- Mid-dilated (4-6 mm)
- Fixed (poorly reactive or non-reactive)
- Oval shape
Anterior Segment
- Ciliary injection (red eye)
- Corneal oedema (hazy)
- Shallow anterior chamber
Palpation
- Affected eye feels hard compared to other eye
IOP Measurement
- Tonometry: Often over 40 mmHg (can be 60-80+)
Gonioscopy
- Closed angle (no trabecular meshwork visible)
6. Investigations
Clinical Diagnosis
- Primarily clinical — classic features
Tonometry
- IOP measurement essential
- Often over 40 mmHg
Slit Lamp
- Corneal oedema
- Shallow anterior chamber
- Cells/flare
Gonioscopy
- Confirms closed angle
Imaging
- Anterior segment OCT (if available)
Classification & Staging
By Mechanism
| Type | Mechanism |
|---|---|
| Pupil block | Most common; aqueous trapped behind iris |
| Plateau iris | Ciliary body pushes iris forward |
| Phacomorphic | Swollen cataractous lens |
| Neovascular | New vessels in angle |
By Duration
- Acute (sudden onset)
- Subacute (recurrent, self-limiting attacks)
- Chronic (gradual angle closure)
7. Management
Immediate — Reduce IOP
Position:
- Supine (allows lens to fall back)
Topical Medications:
| Agent | Class | Effect |
|---|---|---|
| Pilocarpine 2-4% | Miotic | Constricts pupil, opens angle |
| Timolol 0.5% | Beta-blocker | Reduces aqueous production |
| Apraclonidine 1% | Alpha-agonist | Reduces aqueous production |
| Latanoprost | Prostaglandin | Increases uveoscleral outflow |
Systemic Medications:
| Agent | Effect |
|---|---|
| IV acetazolamide 500mg | Carbonic anhydrase inhibitor; reduces aqueous |
| IV mannitol 20% | Osmotic diuretic; reduces vitreous volume |
Note: Pilocarpine may not work if IOP very high (iris sphincter ischaemic)
Definitive Treatment — Laser Peripheral Iridotomy (LPI)
- Creates hole in peripheral iris
- Relieves pupil block
- Allows aqueous to drain
- Both eyes treated (fellow eye prophylaxis)
If Laser Not Possible
- Surgical peripheral iridectomy
- Lens extraction (if lens contributing)
Analgesia and Antiemetics
- IV morphine, ondansetron as needed
Refer Urgently to Ophthalmology
- Same-day assessment essential
8. Complications
Of AACG
- Permanent vision loss
- Optic nerve damage
- Corneal decompensation
- Cataract
- Synechiae (iris adhesions)
Of Treatment
- LPI: Glare, blurred vision (usually minor)
- Systemic medications: Electrolyte disturbance, paraesthesia
9. Prognosis & Outcomes
Prognosis
- Good if treated within hours
- Permanent damage if delayed over 24-48 hours
Vision Outcome
- Depends on duration and peak IOP
- Some recovery possible with prompt treatment
Fellow Eye
- High risk — prophylactic LPI indicated
10. Evidence & Guidelines
Key Guidelines
- Royal College of Ophthalmologists Guidelines
- AAO Preferred Practice Pattern: Primary Angle Closure
Key Evidence
- Laser peripheral iridotomy is definitive treatment
- Prophylactic iridotomy prevents attacks in fellow eye
11. Patient/Layperson Explanation
What is Acute Glaucoma?
Acute glaucoma happens when the fluid in your eye can't drain properly, causing the pressure inside the eye to rise suddenly. This is an emergency.
Symptoms
- Severe pain in one eye
- Red eye
- Blurred vision
- Seeing haloes around lights
- Feeling sick or vomiting
What Should I Do?
- Go to A&E immediately
- This needs urgent treatment to save your sight
Treatment
- Eye drops and tablets to lower the pressure
- Laser treatment to make a small hole in the iris to help fluid drain
Resources
12. References
Primary Guidelines
- AAO. Primary Angle Closure Disease Preferred Practice Pattern. 2020.
- Royal College of Ophthalmologists. Guidelines for the Management of Angle Closure. 2018.
Key Reviews
- Wright C, et al. Primary angle closure glaucoma: an update. Acta Ophthalmol. 2016;94(3):217-225. PMID: 26303815
- Prum BE Jr, et al. Primary Angle Closure Preferred Practice Pattern Guidelines. Ophthalmology. 2016;123(1):P1-P40. PMID: 26581557