After filtering surgery for primary open-angle glaucoma in a 64-year-old man, a persistent wound leak was encountered from the fornix-based conjunctival flap. Cyanoacrylate adhesive was applied but was unsuccessful in sealing the leak. The limbal margin was sutured with 10/0 nylon. One week later a corneal subepithelial fistulous track developed from the edge of the bleb and extended across the cornea towards the inferonasal limbus. The inferior end of the track leaked aqueous. Further surgery was performed to refashion the conjunctival bleb, ablate the fistula at its origin and re-form the anterior chamber. The track recurred 16 days later. The upper cornea was then treated with cryotherapy, which successfully closed the track with maintenance of a functional bleb (ocular pressure 6 mmHg). A faint asymptomatic subepithelial scar persisted.