Acute Angle Closure Glaucoma Despite Patent Peripheral Iridotomy: A Diagnostic And Management Challenge

To highlight the risk, mechanism and management of angle closure despite patent peripheral iridotomy.

Ophthalmology Outpatient Department, Barnsley Hospital NHS Foundation Trust.

A 72-year-old lady with a history of primary angle closure glaucoma in her left eye, treated 14 years prior with bilateral laser peripheral iridotomy, presented with acute onset of left ocular pain, reduced vision, headache, and nausea. Examination revealed conjunctival injection, corneal oedema, a mid-dilated pupil, a diffusely shallow anterior chamber (1.77 mm depth), and intraocular pressure (IOP) of 71 mmHg.

Gonioscopy confirmed a patent iridotomy but revealed 360° appositional angle closure. Anterior segment assessment and AS-OCT showed a thick crystalline lens (5.44 mm) with significant anterior vaulting and cataractous changes, consistent with a lens-driven mechanism of angle crowding rather than plateau iris configuration.

Initial medical management included intravenous acetazolamide, a topical beta-blocker, an alpha-agonist, and a prostaglandin analogue, resulting in partial IOP reduction. Given the lens-induced component, the patient underwent expedited cataract extraction. Postoperatively, the anterior chamber deepened, the angle opened, and IOP normalised without further intervention.

This case highlights several important clinical considerations; a patent iridotomy does not always preclude acute angle closure. Progressive lens thickening may precipitate closure despite the elimination of pupillary block. Careful assessment is essential to distinguish between plateau iris and phacomorphic mechanisms. Finally, early lens extraction may represent definitive management.

Acute angle-closure glaucoma in the presence of a patent iridotomy is an important diagnostic pitfall. Failure to recognise lens-driven angle crowding can result in recurrent attacks and suboptimal long-term IOP control. Similarly, failure to recognise alternative mechanisms may delay definitive treatment. Lens-induced anterior segment crowding should be considered in patients with shallow anterior chambers and cataract, and timely cataract extraction may provide definitive anatomical correction and pressure control.