The failing filtering bleb

Successful bleb creation entails intraoperative adjustment of scleral flap resistance to ensure continuous flow. The use of topical steroids and antimetabolites retards excessive bleb healing after surgery. The investigation of failing blebs entails taking a relevant history and performing a stepwise evaluation at the slit lamp, with the aid of gonioscopy and often of a Ritch or Hoskins lens to view the interior structures of blebs, to determine the site of obstruction. Modalities of treatment include reinstituting medical therapy to allow Tenon's cyst blebs to mature, using topical steroids to treat rebound iritis, using laser suture lysis, the Traverso maneuver to gape the scleral wound, scleral flap needling to adjust scleral resistance to flow, and occasionally needling of Tenon's cyst blebs. When blebs cannot be saved, plans should be made to perform a repeat filter with mitomycin C if a superior limbal location and unscarred conjunctiva is available or to implant a large-reservoir glaucoma drainage device.