Acute Angle Closure Glaucoma

Acute primary angle closure (APAC) is sudden, near complete closure of the anterior chamber angle with abrupt rise in intraocular pressure (often 40 to 80 mmHg), an ophthalmic emergency requiring treatment within hours to prevent irreversible optic nerve damage.

• Pupillary block in an anatomically predisposed eye (shallow chamber, short axial length, thick lens), triggered by mid-dilated pupil in dim light, stress, mydriatic or anticholinergic drugs (atropine, antihistamines, tricyclic antidepressants, ipratropium nebulisers, topiramate, adrenaline), or sulfonamide related ciliochoroidal effusion.
• Peak age 55 to 70, women more than men, hypermetropes, Asian people.
• Fellow eye has about 40 to 80 percent risk of attack within 5 to 10 years without prophylactic iridotomy.

• Severe unilateral eye pain and headache, often brow ache, nausea and vomiting (can be mistaken for an abdominal or neurological emergency), blurred vision, haloes around lights.
• Red eye with ciliary (circumcorneal) injection, corneal epithelial oedema ("steamy" cornea), shallow anterior chamber, mid-dilated fixed oval pupil (4 to 6 mm), raised intraocular pressure with a hard eye on palpation.
• Anterior chamber cells and flare, glaukomflecken (anterior subcapsular lens opacities) after repeated or prolonged attacks, iris atrophy, optic disc oedema.
• Fellow eye: shallow chamber and narrow angle.

• Visual acuity, tonometry (Goldmann; gentle Tonopen if cornea is oedematous), pupil examination, slit lamp (shallow chamber, anterior chamber activity).
• Gonioscopy (after corneal clearing with topical glycerol 50 to 100 percent, or after pressure lowering) shows closed angle; examine the fellow eye gonioscopically.
• Anterior segment optical coherence tomography if available.
• Exclude secondary angle closure: neovascularisation, lens subluxation, uveitis, malignant glaucoma, intraocular tumour.
• Systemic assessment before osmotic agents or acetazolamide: renal function, cardiac status, sulphonamide allergy.

• Immediate pressure reduction (start within the first hour):
  • Acetazolamide 500 mg intravenously (or orally 500 mg if vomiting not severe), then 250 mg orally four times daily. Avoid in sulphonamide allergy and with severe renal impairment; give potassium monitoring.
  • Topical timolol 0.5 percent, apraclonidine 1 percent or brimonidine 0.2 percent, one drop each, with prednisolone acetate 1 percent every 15 to 30 minutes initially for inflammation.
  • Pilocarpine 2 percent one drop every 15 minutes for 2 doses once pressure is lower (the sphincter becomes ischaemic and non-responsive above 40 to 50 mmHg), then four times daily; avoid heavy use because it may worsen block via lens iris diaphragm movement.
  • If pressure remains above 40 mmHg after 1 hour: intravenous mannitol 20 percent 1 to 1.5 g/kg over 30 to 45 minutes (caution in cardiac failure, renal failure, elderly), or oral glycerol 1 to 1.5 g/kg (caution in diabetes).
• Supportive: analgesia (paracetamol, opioid if required), antiemetic (ondansetron 4 mg or metoclopramide 10 mg), lying supine, corneal indentation with a gonioscopy lens or cotton bud to break the block.
• Definitive: laser peripheral iridotomy as soon as the cornea clears and pressure falls (within 24 to 48 hours), Nd:YAG with pilocarpine pretreatment; if the cornea remains hazy, laser iridoplasty (500 micrometre spots, 200 to 400 mW, 0.5 seconds, 20 to 24 spots) or anterior chamber paracentesis or lens extraction.
• Prophylactic laser iridotomy to the fellow eye promptly (within days).
• Follow up: gonioscopy after iridotomy, repeat pressure and optic nerve assessment, and early lens extraction or filtering surgery if pressure remains raised (in synechial closure of over 180 degrees).
• Advise avoidance of dilating agents until iridotomy is done and review of drugs.