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Chronic Angle Closure Glaucoma

ROUTINE — Glaucoma

Symptoms

  • Usually asymptomatic until the disease is in an advanced stage.
  • Progressive visual field loss or decreased visual acuity in late cases.
  • Intermittent blurred vision, headaches, or mild eye pain (subclinical attacks).

Clinical Findings

Epidemiology

  • A leading cause of irreversible blindness worldwide, particularly in East and South Asian populations.
  • Frequently as common as primary open-angle glaucoma (POAG) but often missed due to lack of symptoms.
  • Mandatory finding: Requires gonioscopy on every new glaucoma workup.

Gonioscopy (hallmark signs)

  • Peripheral anterior synechiae (PAS): Iris adhesions to the trabecular meshwork blocking angle structures.
  • "Creeping" closure: Gradual, asymptomatic advancement of the iris root over the meshwork.
  • Synechial progression: Often begins superiorly and moves inferiorly.
  • Indentation gonioscopy: The key to distinguishing reversible appositional contact from permanent synechial closure.

Structural & functional damage

  • Glaucomatous optic nerve damage and visual field defects analogous to POAG.
  • Elevated intraocular pressure (IOP), which may be asymmetric.

The Eagle trial (2016)

  • For patients ≥50 with PACG/PAC and IOP >30 mmHg, clear-lens extraction was more effective than LPI.
  • Demonstrated superior IOP control and improved quality-of-life scores.

Etiology

Primary mechanism

  • Gradual angle narrowing from prolonged appositional closure or repeated subclinical attacks.

Secondary causes

  • Formation of PAS following a flat anterior chamber (due to trauma, surgery, or hypotony).

Risk factors

  • Highest prevalence in East Asian, South Asian, and African populations.
  • Anatomical predisposition (shallow AC, high iris insertion).

Red Flags

  • PAS progression despite a patent LPI: May require surgical goniosynechialysis.
  • Acute-on-chronic presentation: Sudden pressure spikes on an already narrowed angle.
  • Fellow eye status: 50% risk of closure within 5 years without prophylactic LPI.
  • Silent progression: Advanced visual field loss is often the first symptom reported by the patient.

Investigations

Clinical assessment

  • Bilateral indentation gonioscopy to assess the extent of synechial vs. appositional closure.
  • Comprehensive baseline glaucoma workup including IOP and pachymetry.

Imaging

  • Anterior segment OCT or UBM: To identify plateau iris configuration.
  • A-scan biometry: Necessary if planning clear-lens extraction.

Optic nerve & field monitoring

  • Standard automated perimetry (24-2 or 10-2) and OCT RNFL.
  • Baseline optic disc photography.

Treatment

Laser procedures

  • Laser peripheral iridotomy (LPI): Standard first-line for pupillary block; will not reopen fibrotic PAS.
  • Laser iridoplasty: Temporizing measure to reduce new PAS formation.
  • Laser trabeculoplasty (ALT/SLT): Strictly contraindicated; may worsen angle scarring.

Surgical options

  • Clear-lens extraction (lensectomy): Increasingly used as definitive therapy (EAGLE trial).
  • Goniosynechialysis: Surgical iris pulling to open PAS <6 months in duration.
  • Incisional surgery: Trabeculectomy or tube shunt for advanced, medically refractory cases.

Contraindications

  • MIGS: Generally avoided due to poor angle visualization.

Clinical Pearl

Chronic angle closure is a "silent blinder" that hides in plain sight. Indentation gonioscopy is the only way to catch appositional closure before permanent synechiae form. Clear-lens extraction is now often considered first-line for patients over 50.

Differential Diagnosis

  • Primary open-angle glaucoma (POAG)
  • Pseudoexfoliation glaucoma
  • Neovascular glaucoma
  • Steroid-induced glaucoma
  • Intermittent acute angle-closure

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