An artificial trabeculum (MESH) for glaucoma Surgery

To avoid the post-operative hypotony that often occurs with ab interno and ab extemo laser sclerostomies, trabeculectomies, setons and glaucoma implants, we designed the MESH, an implant that mimics the physiological meshwork. It is a sub miniature "T" shaped pouch made of thin porous poly(tetrafluoroethylene) (PTFE). An instrument allows its intrascleral insertion via a 2 mm wide conjunctival incision with the MESH's head protruding in the anterior chamber's angle. Flow was assessed in five PTFE membranes of 5 to 80 μm pore size. Prototype implants were tested for integrity by scanning electron microscopy and in vivo studies were undertaken with MESH implants made of 20 and 50 μm (8 rabbits, 3 months follow-up) and 10 μm (11 rabbits, ongoing) PTFE membranes. Flow rates were 150 to 650 times the normal 2 μ/mn physiological aqueous outflow. Surgery took about 7 minutes. The implants became translucent after 7 days and were found biocompatible over the 3 months follow-up period. The 50 μm implant was biocolonized in 21 days but only a few cells were observed at 3 months in the 20 μm implant which produced a longer lasting bleb and IOP lowering effect. No colonization is expected in the 10 μm material which has a higher flow rate and geometric integrity. The MESH appears safe and efficient in prolonging filtration in rabbits in the short term. To prevent cellular penetration and an adequate regulation of the aqueous flow, an expanded PTFE material with 10-20μmm pores and a 100μm thickness seems best suited for the fabrication of artificial meshwork implants for use in glaucoma patients.