Trabeculectomy and glaucoma drainage devices aim to reduce intraocular pressure (IOP) by draining aqueous humor to the subconjunctival space. Two newer devices, the XEN Gel Stent (Allergan) and the InnFocus MicroShunt (InnFocus/Santen), also produce de novo subconjunctival outflow pathways. The long-term success of any glaucoma filtration operation depends upon maintenance of aqueous humor flow to the subconjunctival space, which can be compromised by postoperative episcleral Tenon fascial fibrosis. Adjuvant antifibrotic agents administered intraoperatively and/or in the early postoperative period have dramatically improved overall success rates by inhibiting fibrosis. This module discusses risk factors and mechanisms that lead to scarring and surgical failure, reviews applications of antifibrotics in glaucoma surgery, and evaluates the roles for these medications within the current glaucoma surgical repertoire. Investigational approaches to the modulation of wound healing in glaucoma surgery also are discussed.