Temporary Filtering Bleb Failure Induced by Anterior Chamber Sulfur Hexafluoride Gas: A Complication after Descemet Membrane Endothelial Keratoplasty

Herein, we report two clinical cases with acute temporary filtering bleb obstruction by gas tamponade after Descemet membrane endothelial keratoplasty (DMEK) surgery and postoperative intraocular pressure (IOP) peaks. Both patients underwent uncomplicated DMEK surgery with 20% sulfur hexafluoride (SF₆) anterior chamber tamponade and had previous trabeculectomy for glaucoma. Prior to surgery, both patients showed patent bleb function with low to normal IOP without antiglaucomatous medication. After uneventful DMEK surgery, both patients showed postoperative IOP peaks of up to 50 mm Hg despite patent inferior iridotomy and no sign of a pupillary block. In both cases, SF₆ gas bubbles could be visualized obstructing the bleb. Both patients were treated with IOP-lowering agents topically as well as systemically. In addition, anterior chamber paracenteses were performed to reduce the SF₆ volume within the anterior chamber. Under this treatment, IOP normalized within the first 18 h after surgery. We hypothesize that the SF₆ gas tamponade from the anterior chamber migrates into the ostium and below the bleb, leading to an acute temporary insufficiency of bleb function and to a consecutive IOP peak after surgery. In contrast to a pupillary block, this mechanism cannot be antagonized by preoperative iridotomy and needs to be taken into account for every glaucoma patient with functional bleb undergoing DMEK surgery.