Subconjunctival Versus Direct Scleral Application of Mitomycin-C in Trabeculectomy

Trabeculectomy is widely used as a surgical treatment of uncontrolled open glaucoma. Success of trabeculectomy at halting or slowing glaucoma progression primarily relies on the extent of conjunctival and sclera wound healing. The success rates of trabeculectomy increased dramatically with the introduction of anti-metabolites. For more than two decades mitomycin-c (MMC), a chemotherapeutic agent capable of decreasing fibroblast activity and modulating wound healing at the bleb, has been used with trabeculectomy. The complications of MMC are well known and several studies have described various methods of application based on exposure time, dose and surface area. Numerous retrospective and prospective studies have compared the efficacy of MMC applied beneath the conjunctival flap with soaked sponges versus intrascleral application. In 2008, Lee et al. first described an alternative route of application: subconjunctival injection of MMC directly into the intra-Tenon area. Seventy-six eyes with primary and secondary open angle glaucoma underwent trabeculectomy with this approach and were followed for one year post-operatively. Eighty-six percent of eyes achieved an IOP <21 mm Hg and 57% an IOP<14 mm Hg at one year without adjunctive drops. Transient complications included hyphema, bleb leak and choroidal detachment. The advantages of injected MMC are primarily in controlling the exact dosage and area of application and reduced surgical time. Lim et al. retrospectively reviewed the outcomes of trabeculectomy in 57 eyes using sponge application directly to the sclera versus intra-tenon injection. IOP was significantly lower in the injection group at 1 month, 1, 2, and 3 years. Trabeculectomy success (IOP<21mm Hg or IOP >20% below baseline without medications or additional surgery) was greater in the injection group at 3 years. The sponge group experienced more encapsulated blebs but complication rates were similar in both groups. To date, there have been no prospective studies comparing the IOP-lowering efficacy and safety of intra-tenon injection versus direct scleral application of MMC.