What causes closed-angle glaucoma?

Causes of Closed-Angle Glaucoma

Closed-angle glaucoma is primarily caused by pupillary block, where pressure in the posterior chamber exceeds that in the anterior chamber, causing anterior bowing of the iris that crowds the angle in anatomically predisposed eyes. 1

Primary Mechanisms

1. Pupillary Block (most common mechanism)

   • Resistance to aqueous humor flow between the iris and lens
   • Creates pressure differential between posterior and anterior chambers
   • Results in anterior iris bowing and angle crowding 2, 1

2. Non-pupillary Block Mechanisms

   • Plateau iris configuration/syndrome: abnormal ciliary body position and iris insertion 1
   • Peripheral iris crowding 3
   • Lens-related factors 3
   • Retrolenticular mechanisms 3

Anatomical Risk Factors

The following ocular features predispose to closed-angle glaucoma:

• Anterior Chamber Characteristics

  • Shallow peripheral anterior chamber depth 2
  • Shallow central anterior chamber depth 2

• Eye Structure Factors

  • Hyperopia (farsightedness) 2, 1
  • Steep corneal curvature 2, 1
  • Thick crystalline lens 2, 1
  • Short axial length 2, 1
  • Anterior lens position 1

• Iris and Ciliary Body Configuration

  • Anterior rotation of ciliary body 1
  • Abnormal iris insertion into ciliary body 1

Demographic Risk Factors

• Ethnicity: Higher prevalence in Asian populations, particularly Chinese and Inuit 2, 1
• Age: Typically affects adults over 50 years 2, 1
• Gender: More common in females 1
• Family history: Genetic predisposition 1

Pathophysiological Progression

Closed-angle glaucoma typically develops through a sequence of stages:

1. Primary angle-closure suspect (PACS): ≥180° of iridotrabecular contact (ITC) without elevated IOP or peripheral anterior synechiae (PAS) 2, 1

2. Primary angle closure (PAC): ITC with either elevated IOP or PAS, but no optic neuropathy 2, 1

3. Primary angle-closure glaucoma (PACG): Glaucomatous optic neuropathy due to sustained or intermittent IOP elevation 1

4. Acute angle-closure crisis (AACC): Sudden complete angle obstruction causing rapid IOP elevation, presenting with corneal edema, mid-dilated pupil, eye pain, headache, nausea/vomiting 1

Clinical Implications

Without treatment, closed-angle glaucoma can lead to severe visual impairment. After an acute angle-closure crisis:

• 18% of eyes may become blind
• 48% develop glaucomatous optic neuropathy
• 58% have visual acuity worse than 20/40 within 4-10 years 2, 1

Common Pitfalls in Diagnosis

• Failing to perform gonioscopy in patients with risk factors
• Missing plateau iris configuration, which can cause recurrent IOP spikes even after iridotomy 2
• Not evaluating the fellow eye in patients with unilateral acute angle closure (high risk for developing angle closure) 2
• Overlooking medication-induced angle closure (particularly from adrenergic agents, anticholinergics, and some antidepressants) 1

Understanding these mechanisms and risk factors is essential for early identification and management of patients at risk for closed-angle glaucoma, as timely intervention can prevent irreversible vision loss.