A 58-year-old woman presents with acute onset of severe eye pain, blurred vision, and haloes around lights in her right eye. Examination reveals a mid-dilated pupil, corneal oedema, shallow anterior chamber, and intraocular pressure of 58 mmHg. Gonioscopy shows angle closure. All of the following are characteristic features of acute primary angle-closure glaucoma EXCEPT:

Explanation

## Understanding Acute Primary Angle-Closure Glaucoma ### Pathophysiology of PACG **Key Point:** Acute primary angle-closure glaucoma results from sudden obstruction of the trabecular meshwork by peripheral iris tissue, typically triggered by pupillary dilation in anatomically predisposed eyes (shallow anterior chamber, short axial length, hyperopia). ### Characteristic Features of Acute PACG | Feature | Details | Mechanism | |---------|---------|----------| | **Posterior iris bowing** | Iris pushed backward against lens | Relative pupillary block; aqueous pressure builds up behind iris | | **IOP elevation** | Usually 40–80 mmHg (can exceed 60 mmHg) | Sudden trabecular meshwork obstruction | | **Corneal oedema** | Hazy, cloudy cornea | Endothelial decompensation from acutely elevated IOP | | **Mid-dilated pupil** | Pupil fixed, mid-position | Iris ischaemia and sphincter paralysis | | **Shallow AC** | Anterior chamber appears very shallow | Anatomical predisposition | ### Why Option 2 (Peripheral Iridotomy) Is the Answer **High-Yield:** A peripheral iridotomy performed during the acute attack **relieves the acute episode** but does **NOT permanently resolve** the underlying anatomical predisposition. The eye remains at risk for angle closure in the contralateral eye and can develop chronic angle-closure glaucoma even after successful iridotomy if the angle remains narrow. **Clinical Pearl:** Although iridotomy is the definitive treatment for acute PACG and prevents recurrence in the affected eye, it does not guarantee permanent resolution of glaucoma in that eye—some patients develop chronic angle-closure or elevated IOP despite patent iridotomy due to persistent angle narrowness or lens-induced mechanisms. **Key Point:** The statement "peripheral iridotomy permanently resolves the acute attack" is misleading. While iridotomy relieves the acute attack, it does not permanently resolve all cases; some patients still require additional management (laser cyclophotocoagulation, glaucoma surgery) if IOP remains elevated or angle remains narrow. ### Why Each Distractor Is Correct - **Option 0 (Posterior iris bowing):** This is a hallmark finding in acute PACG due to relative pupillary block; aqueous accumulates behind the iris, pushing it backward. - **Option 1 (IOP > 40 mmHg):** Acute PACG characteristically presents with markedly elevated IOP, typically 40–80 mmHg or higher. - **Option 3 (Corneal oedema):** Corneal oedema is a cardinal sign of acute PACG, caused by endothelial cell decompensation from the acutely elevated IOP.