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 of Angle Closure

1. Pupillary Block (Most Common)

• Impaired aqueous humor flow from posterior to anterior chamber creates pressure differential
• Results in anterior iris bowing that narrows or closes the drainage angle
• Accounts for majority of primary angle closure cases 1, 2

2. Anatomical Predispositions

• Ocular Features That Increase Risk:
  • Hyperopia (farsightedness)
  • Shallow anterior chamber depth (both peripheral and central)
  • Steep corneal curvature
  • Thick crystalline lens
  • Short axial length
  • Anterior lens position 1, 3, 4

3. Additional Contributing Mechanisms

• Ciliary Body Position and Iris Insertion:

  • Anterior rotation of ciliary body (plateau iris configuration)
  • Abnormal iris insertion into ciliary body
  • Increased iris volume 1

• Lens-Related Factors:

  • Age-related lens thickening
  • Forward lens positioning
  • Changes in lens shape or position 1, 2

Pathophysiological Progression

1. Initial Stage: Iridotrabecular contact (ITC) develops when iris touches posterior trabecular meshwork

   • Defined as primary angle-closure suspect when ≥180° of ITC is present 1

2. Intermediate Stage: Primary angle closure occurs when ITC is accompanied by:

   • Elevated intraocular pressure (IOP), and/or
   • Development of peripheral anterior synechiae (PAS) 1

3. Advanced Stage: Primary angle-closure glaucoma develops when:

   • Glaucomatous optic neuropathy occurs due to sustained or intermittent IOP elevation 1

4. Acute Presentation: Acute angle-closure crisis (AACC) occurs when:

   • Sudden complete angle obstruction causes rapid IOP elevation
   • Presents with corneal edema, mid-dilated pupil, eye pain, headache, nausea/vomiting 1, 2

Special Considerations

Plateau Iris Configuration and Syndrome

• Characterized by angle closure despite deep central anterior chamber
• Caused by anterior rotation of ciliary body
• Can persist after iridotomy
• May cause recurrent IOP spikes even after iridotomy (plateau iris syndrome) 1

Demographic Risk Factors

• Higher prevalence in:
  • Asian populations (especially Chinese, Inuit)
  • Women
  • Older adults (typically >50 years)
  • Family history of angle closure 1, 2, 4

Clinical Implications

• Without treatment, AACC can cause permanent vision loss or blindness
• Fellow eye is at high risk for developing AACC
• Even after resolution of acute episode, continued monitoring is essential
• Long-term outcomes without treatment are poor: 18% blindness rate, 48% developing glaucomatous optic neuropathy 1, 2

Prevention and Management Considerations

• Laser iridotomy is the primary intervention to eliminate pupillary block
• Lens extraction may be effective for some patients with PAC and PACG
• Fellow eye should undergo prophylactic laser iridotomy when indicated
• Plateau iris syndrome may require additional interventions beyond iridotomy 1, 2

Understanding these causative mechanisms is essential for proper diagnosis, prevention, and management of closed-angle glaucoma to prevent irreversible vision loss.