Evaluation of bleb characteristics after implantation of the EX-PRESS(™) glaucoma filtration device

PURPOSE: To compare bleb survival and histology after implantation of the EX-PRESS™ glaucoma filtration device versus silicone tubes in a rabbit model of filtration surgery. METHODS: Glaucoma filtration surgery was performed on one eye each of twelve New Zealand white rabbits. Eyes were randomized to implantation with the EX-PRESS™ filtration device (n=6) or a silicone tube (n=6). Bleb vascularity was evaluated at three and six weeks using a standard scale. At 6 weeks, eyes were enucleated and a histologic analysis was performed. Bleb survival was also recorded for the two groups. RESULTS: Histologically, a thin capsule consisting of mild fibroblast proliferation associated with intercellular collagen was present around both implants. Both groups demonstrated a mild infiltration of plasma cells and polymorphonuclear leukocytes. Bleb vascularity was similar between both groups at three and six weeks post-operatively. Bleb survival between the two groups was not significantly different. CONCLUSIONS: Similar outcomes were noted after glaucoma filtration surgery using either silicone tubes or the EX-PRESS™ glaucoma filtration device in this rabbit model. Both implants appear to be relatively inert with little difference in biocompatibility and bleb survival.