OP7.3 | Primary Angle Closure Glaucoma — Summary & Reflection

KEY TAKEAWAYS

Primary angle closure glaucoma (PACG) results from pupil block — aqueous accumulates in the posterior chamber due to impaired flow through the pupil, bowing the iris forward (iris bombe) and occluding the trabecular meshwork. The angle is CLOSED on gonioscopy — the defining structural opposite of POAG. Risk factors: hypermetropia, short axial length, shallow anterior chamber, thick lens, female sex, East/South Asian ethnicity. An acute PACG attack is an ophthalmic EMERGENCY: severe ocular pain, nausea/vomiting, coloured haloes, sudden vision loss, mid-dilated fixed pupil, hazy cornea, IOP 50–80+ mmHg. Emergency management sequence: IV mannitol (osmotic, fastest) + IV acetazolamide (CAI) + pilocarpine 2% (miotic — opens angle by constricting pupil; RIGHT for PACG, NOT for POAG) + topical timolol + supine position. Definitive treatment: Nd:YAG laser peripheral iridotomy (LPI) to BOTH eyes — eliminates pupil block permanently. The fellow eye must ALWAYS be treated prophylactically. EAGLE trial supports early clear lens extraction as an alternative. CRITICAL CONTRAST: PACG uses pilocarpine (miotic) as an emergency; POAG uses prostaglandin analogues (latanoprost) as first-line maintenance — these treatments are type-specific and must never be confused.

REFLECT

Recall the woman from the hook — she came to the emergency department with headache, nausea, and vomiting, and the initial physician considered migraine. The ocular component was only recognised when the intern examined the eye carefully. Reflect on the systemic presentation of an ophthalmic emergency: how often might acute PACG be misdiagnosed as migraine, gastroenteritis, or 'stress' in a patient who presents at a general emergency or primary care setting? What elements of the history — coloured haloes, unilateral eye pain, poor vision in one eye — should trigger immediate ocular examination? And consider the preventive dimension: this woman's fellow eye almost certainly has the same narrow angle. Had she known about her anatomical predisposition, an elective LPI could have prevented this emergency entirely. How would you counsel her about her fellow eye and about medications that could precipitate a future attack?