Control of filtering bleb structure through tissue bioengineering: An animal model

PURPOSE: To devise a means of providing controlled resistance between the anterior chamber and the subconjunctival space after trabeculectomy by implantation of a biodegradable, porous collagen matrix. METHODS: Matrices were implanted in the right eyes of 17 rabbits after trabeculectomy, while left eyes served as surgical controls. The scleral flap was sutured loosely, and the implant provided pressure on the scleral flap to reduce overfiltration. Trabeculectomy in the control eyes was performed with tight sutures using standard methodology. Intraocular pressure (IOP) was measured before surgery and on days 3, 7, 14, 21, and 28 after surgery. Masson trichrome and alpha-smooth muscle actin stains were used for histologic study of the filtering blebs. RESULTS: The initial postoperative IOP reduction was approximately equal, at 14% to 16%, for both groups. In the implanted group, the IOP continued to decrease to 55% below baseline at day 28 as the implant gradually degraded. In the control group, IOP had returned to the preoperative level by day 21. Histologic examination with Masson trichrome and alpha-smooth muscle actin stains showed a prominent bleb in the implanted group compared with scar formation and limited bleb formation in the control group. CONCLUSIONS: Implantation of a biodegradable, porous collagen matrix in the subconjunctival space offers the potential for a new means of avoiding early scar formation and maintaining long-term IOP control by creating a loosely structured filtering bleb.