A patient with POAG is being managed with maximum tolerated medical therapy but continues to progress. He undergoes trabeculectomy. Six weeks post-operatively, the IOP is unexpectedly elevated to 32 mmHg, the bleb is flat and avascular, and gonioscopy shows the ostium is open. What is the most likely cause of surgical failure?
- A Suprachoroidal haemorrhage
- B Internal ostium block by vitreous prolapse
- C Aqueous misdirection (malignant glaucoma)
- D Subconjunctival fibrosis and bleb failure ✓
Explanation
A flat, avascular bleb with elevated IOP and an open internal ostium indicates subconjunctival fibrosis sealing the filtering pathway — the most common cause of late trabeculectomy failure. Tenon's capsule fibroblasts proliferate and scar the subconjunctival space, preventing aqueous filtration. Suprachoroidal haemorrhage presents acutely with severe pain and hypotony followed by IOP spike, not a delayed course. Vitreous block occurs in aphakic or post-vitrectomy eyes. Malignant glaucoma presents with flat anterior chamber and forward lens displacement rather than a flat bleb.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.