Glaucoma drainage devices (GDDs) have widely been used in the treatment of high-risk refractory glaucoma. To avoid tube exposure, which may lead to serious eye infection, the implanted GDD tube must be covered by a patch graft traditionally made of either donor sclera or pericardium. However, these patch grafts still carry a high rate of progressive thinning and erosion, a complication that we speculate results from the lack of cellular infiltration from the surrounding host conjunctival stroma and poor integration of these patch grafts to the host tissue. We further speculate that a thicker version of cryopreserved amniotic membrane (AM), manufactured by Bio-Tissue, Inc., a 100%-owned subsidiary of TissueTech, Inc., could offer better tensile strength, be suitable for tectonic support, and have biological activities to promote cellular infiltration by the surrounding host conjunctival stroma, thus reducing progressive allogeneic patch graft thinning/erosion. Through SBIR Phase I grant support (R43 EY19785), we have evaluated the thicker AM as an alternative patch graft for covering the GDD tube during the primary implantation. We further monitored the host cell interaction using anterior segment optical coherence tomography (OCT). We have successfully accomplished the proposed aims of the above studies which demonstrated the short-term stability/efficacy of AM in covering the tube in primary GDD surgery (Phase I- Aim 1), and confirmed the feasibility of using OCT to distinguish host cell infiltration into the AM after transplantation over the GDD tube (Phase I- Aim 2). In this Phase II application, we propose to conduct a prospective, controlled study to compare the long-term safety and efficacy of the thicker AM (AmnioGuard"""""""", Bio-Tissue, Inc, Miami, FL) to the pericardium (Tutoplast(R), IOP Inc, Costa Mesa, CA) in securing the GDD tube and reducing tube exposure and graft thinning in patients with high risk glaucoma. We will also study the risk factors that may contribute to GDD tube exposure. Accomplishment of this Phase II study will position AM as an effective alternative to the existing patch grafts to reduce tube exposure and enhance the success of GDD implantation while providing a better aesthetic appearance and allowing visualization of the tube in patients with high risk glaucoma. This will also allow the Company to expand its market space from ocular surface to glaucoma diseases. We speculate that such a graft might also have other clinical applications outside of covering GDD tubes.
Our proposed prospective, randomized and comparative study described in this Phase II application aims to demonstrate the clinical safety and efficacy of transplanting a thicker version of amniotic membrane (AM) as an alternative tectonic substrate to cover glaucoma drainage device (GDD) tubes. Through SBIR Phase I grant support (EY019785), we found that this thicker AM offers superior tectonic support and biological activity to promote integration by the host conjunctival stromal cells, thus reducing patch graft thinning/erosion. The completion of the study described herein will allow eye surgeons to adopt this new AM graft to improve surgical outcomes and prevent complications in GDD surgery for high risk glaucoma patients. This will also allow the Company to expand its market space and provide services to glaucoma indications.