Primary Angle Closure

0.1% of over 40s

1.5% of Chinese population over 50

Risk factors

• Demographic

  • Age >40
  • Female
  • Ethnicity: chinese, south east asian

• Anatomical

  • Narrow angle/shallow AC
    • Anterior iris-lens diaphragm
    • Large lens/cataract
    • Small corneal diameter
    • Short axial length (hypermetropic)
    • Lens thickness-to-axial length ratio

• Nanophthalmos: bilateral short globes (<20mm) with hyperopia, reduced corneal diameter <12mm and thick sclera (impedes uveoscleral outflow).The eye is uniformly reduced in size but the lens is normal or enlarged and the sclera is abnormally thick

• Pupillary block: most common mechanism

  • Increased risk in microspherophakia (found in Weill-Marchesani syndrome)

• Plateau iris

  • Anteriorly placed ciliary body that apposes the peripheral iris
  • AC depth is normal centrally but shallow peripherally
  • Double-hump sign on gonioscopy
  • Plateau-iris syndrome: iris bunches up peripherally and blocks trabeculum (may cause angle closure despite patent PI) see below section

Classification

• Narrow angle: after dark-room gonioscopy in primary position

• Iridotrabecular contact (ITC): on gonioscopy

• Primary angle closure (PAC): ITC plus raised IOP or peripheral anterior synechiae or symptoms

  • Primary angle closure suspect (PACS): >2 quadrants (180 degrees) of ITC but normal IOP, no PAS, normal optic nerve
  • Zhongshan Angle Closure Prevention Study (ZAP): found limited benefit of prophylactic PI for PAC suspects, therefore widespread PI for PACS was not recommended
  • Consider cataract surgery if IOP >30 (or PACG) with visually significant lens opacity (EAGLE RCT showed clear-lens extraction was as effective but with better IOP control and better QoL compared to standard care with PI and topical medications)

• Acute primary angle closure: ITC with symptomatic raised IOP

• Primary angle closure glaucoma: PAC with disc and/or VF changes

  • YAG PI is important but beware of IOP spikes if significant peripheral anterior synechiae
  • Medical and surgical treatment as for POAG
  • Beware of increased risk of aqueous misdirection syndrome

Clinical features

• Pain
• Blurred vision
• Haloes
• nausea/vomiting
• Red eye
• Raised IOP
• Corneal oedema
• Closed angle
• Fixed semi-dilated pupil
• Iris atrophy/transillumination defects
• Glaucomflecken: white flecks representing degenerated lens epithelium due to severe raised IOP, seen just beneath the anterior capsule
• Contralateral narrow angle
• Shallow AC

Management of acute primary angle closure

1. Systemic acetazolamide: 500mg IV stat then 250mg oral QDS
2. Topical: beta-blocker (timolol), sympathomimetic (apraclonidine), steroid (maxidex), pilocarpine 2% (twice in first hour then QDS)
3. Admission
4. Corneal indentation with 4-mirror goniolens may help relieve pupil block
5. Lying patient supine may help lens to fall away from iris
6. Pilocarpine 1% to contralateral eye while awaiting YAG PI
7. Hourly IOP check
8. Systemic hyperosmotic if IOP not improving: mannitol 20% solution 1-1.5g/kg IV
9. Acute YAG PI if IOP still not improving (topical glycerin can temporarily reduce corneal oedema)
10. IOP still high: review diagnosis ?aqueous misdirection; consider repeating or surgical PI, argon iridoplasty, paracentesis, cyclodiode, emergency cataract extraction
11. Bilateral laser or surgical PI is definitive
12. Long-term chronic IOP due to synechial closure may require topical/surgical treatment

Mannitol

• Hyperosmotic: increases blood osmolality to draw water out of the vitreous
• Faster administration and large dose will increase the gradient and thus give a more potent effect
• Less effect when the blood-aqueous barrier is disrupted (eg. uveitis)
• Increase cardiac preload: avoid use in congestive heart failure, renal failure/dialysis patients, also risk of cerebral complications