Acute angle-closure glaucoma
A sudden mechanical blockage of aqueous outflow at the iridocorneal angle causes a rapid, severe rise in intraocular pressure, producing an excruciatingly painful red eye with visual loss that is an ophthalmic emergency.
In a nutshell
Aqueous cannot escape through a suddenly blocked iridocorneal angle, most often when a mid-dilated pupil bunches iris tissue into the drainage angle. Intraocular pressure rockets within hours, producing pain, corneal oedema, haloes and visual loss; an emergency treated first with pressure-lowering drugs, then laser iridotomy.
Classic presentation
An older, hypermetropic patient develops sudden severe unilateral eye pain, headache, blurred vision with haloes around lights, and vomiting, often in the evening, with a red eye, hazy cornea and a fixed, mid-dilated pupil.
Key points
- Pupillary block, not simple angle narrowing, is the mechanism: mid-dilation bunches iris into the angle and seals the trabecular meshwork.
- Intraocular pressure can reach 60-80 mmHg within hours, explaining why this is a same-day emergency, not a routine referral.
- The fixed, mid-dilated, oval pupil is a direct sign of ischaemic sphincter paralysis from the pressure, not primary pupil pathology.
- Nausea and vomiting can dominate the picture and mimic an abdominal or neurological emergency, delaying diagnosis.
- The fellow eye shares the anatomical risk and is treated prophylactically with iridotomy even if asymptomatic.
First-line investigation
Tonometry to measure intraocular pressure: it directly confirms the mechanism driving the emergency and guides urgency of treatment.
First-line management
Emergency medical therapy to lower intraocular pressure (topical and systemic agents), followed by urgent ophthalmology referral for definitive laser peripheral iridotomy.
Exam traps
- Do not mistake the vomiting for a gastrointestinal cause; check the eye in any patient with headache, vomiting and visual disturbance.
- Pilocarpine is not given first; it is added once pressure starts falling, as an ischaemic sphincter will not respond to it initially.
- A red eye with a normal, reactive pupil argues against angle closure: the fixed mid-dilated pupil is the discriminating sign.
Educational content pending clinical review. Not medical advice.