Key Facts

AACG causes rapid, irreversible optic nerve damage if not treated promptly. It should be considered in any patient presenting with a painful red eye and reduced vision.

Epidemiology

• Incidence: 12-15 per 100,000 per year (UK)
• Female:male ratio 3:1
• Peak age: >60
• East Asian ethnicity: significantly higher risk (smaller eyes, shallower anterior chambers)
• Hypermetropic (long-sighted) patients at higher risk

Aetiology

• Anatomically predisposed eye (short axial length, shallow anterior chamber, thick lens, narrow angle)
• Pupillary block: mid-dilated pupil causes iris to bow forward → blocks trabecular meshwork
• Precipitants: dim lighting, mydriatic drugs (tropicamide), anticholinergics (oxybutynin, TCAs, ipratropium), sympathomimetics

Pathophysiology

• Pupillary block → iris bows forward → peripheral iris occludes trabecular meshwork → sudden cessation of aqueous outflow → rapid IOP rise (40-80mmHg) → corneal oedema (haze) → optic nerve ischaemia → retinal ganglion cell death

Symptoms

• Severe unilateral eye pain (often frontal/periorbital)
• Reduced/blurred vision
• Haloes around lights (corneal oedema causes light diffraction)
• Nausea and vomiting (vagal response to pain; can mimic acute abdomen)
• Headache (can mimic migraine or stroke)
• Profuse lacrimation

Signs

• Red eye (mixed conjunctival and ciliary injection)
• Hazy/oedematous cornea (steamy)
• Semi-dilated, fixed (non-reactive) pupil — oval shaped
• Rock-hard eye (elevated IOP palpable through closed lids)
• Shallow anterior chamber (by slit lamp or pen torch — narrow shadow sign)
• IOP markedly elevated (often 40-80mmHg)

Red Flags

• This IS a red flag — any presentation matching above requires emergency management
• Fellow eye may have narrow angles (at risk of same episode)
• Misdiagnosis risk: nausea/vomiting → "acute abdomen"; headache → "migraine"

Bedside

• Visual acuity (usually significantly reduced)
• IOP measurement (Goldmann tonometry): markedly elevated; if not available, palpation through closed lids (very firm)
• Pen torch: semi-dilated, oval, fixed pupil; shallow AC (narrow shadow sign)
• Slit lamp: corneal oedema, shallow AC, closed angle (gonioscopy when acute phase resolved)

Bloods

• Not needed for diagnosis
• U&Es if acetazolamide being used (electrolyte disturbance)

Imaging

• Anterior segment OCT/ultrasound biomicroscopy: angle assessment (specialist)
• B-scan ultrasound: if no view of posterior segment

Special Tests

• Gonioscopy: gold standard for angle assessment (performed after acute phase resolved)
• Fellow eye gonioscopy: assess for narrow angles (prophylactic iridotomy needed)

Emergency Treatment (Reduce IOP)

1. Lie patient supine (iris falls back, may partially open angle)
2. Pilocarpine 2% drops to affected eye: every 5 minutes × 3 then 4× daily (constricts pupil → opens angle)
   • Pilocarpine to fellow eye also (prophylactic)
3. Timolol 0.5% drops to affected eye: single dose (reduces aqueous production)
4. IV acetazolamide 500mg STAT (reduces aqueous production; oral 250mg QDS maintenance)
5. Topical steroid (dexamethasone 0.1%): reduces inflammation from acute episode
6. Analgesia: paracetamol ± opioid
7. Antiemetic: cyclizine 50mg IM/IV
8. If IOP not responding: IV mannitol 20% (1g/kg over 20 minutes) — osmotic diuretic
9. Pilocarpine may not work if IOP >50mmHg (sphincter ischaemia); must reduce IOP first with systemic agents

Definitive Treatment

• YAG laser peripheral iridotomy (PI): creates small hole in peripheral iris → bypasses pupillary block → allows aqueous flow to trabecular meshwork
  • Performed once cornea has cleared (usually within 24-48 hours)
  • Both eyes treated (fellow eye prophylactic iridotomy — essential)
• Lens extraction (cataract surgery): removes the thick lens contributing to crowding; increasingly used as primary or early treatment

Surgical/Interventional

• Surgical peripheral iridectomy: if laser not possible
• Lens extraction: if angle-closure recurs despite PI or coexisting cataract
• Goniosynechialysis: to break peripheral anterior synechiae (specialist)

Referral Criteria

• AACG: immediate ophthalmology referral (same day/emergency)
• Fellow eye: prophylactic iridotomy arranged urgently
• Post-acute: ongoing glaucoma monitoring

• Prompt treatment (within hours): good visual prognosis; IOP reduces within hours of treatment
• Delayed treatment: permanent optic nerve damage; visual field loss; blindness
• After laser PI: recurrence is rare; fellow eye protected
• Chronic angle-closure may develop if repeated/prolonged episodes with synechiae formation
• Risk of further episodes in fellow eye is 40-80% without prophylactic treatment

Emergency AACG Treatment Summary

Risk Factors for Angle-Closure