Acute Angle Closure Attack

Acute angle closure is an ophthalmic emergency in which the peripheral iris blocks the trabecular meshwork, aqueous outflow stops and intraocular pressure (IOP) rises abruptly, often to 40 to 80 mmHg. Pupillary block in an eye with a shallow anterior chamber is the usual mechanism.

• Risk factors: age over 50 years, female sex, hypermetropia, short axial length, East African and Asian ancestry, family history, and shallow chamber from an enlarging lens.
• Precipitants: dim light or dusk, mydriatic drops, anticholinergics, tricyclic antidepressants, topiramate, sulfonamide containing drugs, decongestants and adrenergic agents.
• Untreated, irreversible optic nerve damage can occur within hours to days.

Severe unilateral eye pain with ipsilateral headache, blurred vision, haloes around lights, nausea and vomiting.

• Red eye with ciliary flush, hazy oedematous cornea, fixed mid dilated oval pupil, shallow anterior chamber.
• Eye feels hard to palpation through closed lids; IOP above 30 mmHg on tonometry.
• Fellow eye usually shows a narrow angle.
• Subacute or intermittent attacks: haloes and mild blur in the evening with spontaneous resolution.
• Differential diagnosis: acute anterior uveitis, migraine, cluster headache, subarachnoid haemorrhage, acute conjunctivitis, keratitis, neovascular glaucoma, malignant glaucoma, orbital cellulitis, acute gastroenteritis in the vomiting patient.
• Complications: optic neuropathy and permanent field loss, corneal decompensation, peripheral anterior synechiae with chronic angle closure glaucoma, cataract, central retinal vein occlusion, painful blind eye.

Diagnosis is clinical plus tonometry; do not delay treatment for investigations.

• Tonometry (Goldmann or handheld), pupil and anterior chamber assessment with a pen torch and slit lamp.
• Gonioscopy of both eyes once the cornea clears, after IOP is lowered.
• Anterior segment imaging or ultrasound biomicroscopy where available.
• Exclude secondary closure: lens subluxation, uveitis, neovascularisation, tumour.
• Baseline urea, electrolytes and creatinine before acetazolamide and mannitol; glucose; pregnancy test where relevant.

Lower the IOP quickly, relieve the block, then perform definitive laser iridotomy on both eyes.

• Supportive: sit patient upright, analgesia with paracetamol 1 g orally and opioid if severe, ondansetron 4 mg IV or oral for vomiting. Avoid anticholinergic antiemetics.
• Pharmacological: acetazolamide 500 mg IV (or orally if no vomiting) once, then 250 mg orally every 6 hours; timolol 0.5 percent one drop; brimonidine 0.2 percent one drop; prednisolone acetate 1 percent one drop every 15 minutes for 1 hour then four times daily. Pilocarpine 2 percent one drop every 15 minutes for 2 doses once IOP has fallen below about 40 mmHg (the ischaemic sphincter does not respond at very high pressure). If IOP stays high at 1 hour: mannitol 20 percent 1 to 1.5 g/kg IV over 30 to 45 minutes, or oral glycerol 1 to 1.5 g/kg in cold juice.
• Procedures: laser peripheral iridotomy as soon as the cornea is clear enough, prophylactic iridotomy of the fellow eye within days. Anterior chamber paracentesis, laser iridoplasty or lens extraction when laser fails. Trabeculectomy for persistent raised IOP with synechial closure.
• Special groups: pregnancy, give acetazolamide only for a short period and prefer topical agents plus mannitol; heart or renal failure, avoid mannitol and acetazolamide; sulfonamide allergy, avoid acetazolamide; children are rare and nearly always secondary, so refer early.
• Red flags: IOP unresponsive after 1 to 2 hours, vision limited to light perception, bilateral attack, drug induced bilateral closure (topiramate), corneal melt.
• Follow-up: IOP and pupil at 1 hour and after laser, review at 24 hours, 1 week, 1 month, then every 3 to 6 months with gonioscopy, optic disc and visual field assessment. Counsel on avoiding mydriatics and warn of symptoms for the fellow eye.