Filtering blebs fail due to wound healing responses along the path of aqueous outflow (Fig. 37.1). there can be significant subconjunctival fibroblast proliferation and biosynthesis of collagen and other extracellular matrix materials in the area of trabeculectomy . The concept behind bleb needling is to reestablish free flow of aqueous humor from the anterior chamber to the subconjunctival bleb space by cutting through postoperative scar tissue that prevents or decreases aqueous outflow. Needling cuts through adhesions formed between the conjunctiva and scleral flap and/or from scleral flap to scleral bed. A retrospective study of 119 trabeculectomies found that one-quarter of eyes underwent needling to increase the rate of filtering success . As with any procedure, many variations exist with regard to bleb needling technique.
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