Tube occlusion from the external ostium after implantation of an aqueous shunt.

Two patients had undergone double-plate Molteno shunt implantation. Both patients required surgical revision, the first at 41 months and the second at 8 months postoperatively, because of a failure of previously functioning tube shunts caused by blockage of the external ostium and intraluminal invasion of the tube by fibrous tissue. At the time of surgical revision, fibrous tissue extended down the lumen of the tube, occluding its external ostium. After excision of this tissue, both shunts became fully functional. When functioning aqueous shunts fail and there is no evidence of a bleb over the shunt reservoir or blockage of the internal ostium, ingrowth of fibrous tissue into the external ostium should be considered as a potential cause, especially if a ripcord or Latina suture has been left in place.