EXPERIMENTAL EVALUATION OF A HYDROXYLAPATITE RESERVOIR TUBE SHUNT IN RABBITS

BACKGROUND AND OBJECTIVES: Anterior chamber tube shunts of various des ign are of increasing importance in the surgical management of refract ory glaucoma. However, the reservoirs that are commonly used today are made of a silicone or an acrylic material that may become enveloped b y a fibrous capsule, which in turn may impede aqueous resorption. In t his study, the authors investigated the properties of hydroxylapatite (HPI) as a reservoir in gonioimplants, using three different types of HA reservoir designs. It has been demonstrated that HA orbital implant s become vascularized, and the authors hypothesized that this feature of HA might modify the development of the fibrous capsule, enhancing t he efficacy and decreasing the size of the implants. MATERIALS AND MET HODS: HA reservoirs with Silastic tube shunts were implanted in the ri ght eyes of six Dutch-belted rabbits. Clinical examinations were perfo rmed and intraocular pressure was measured periodically for 16 weeks p ostoperatively. Prior to euthanasia, fluorescein-labeled latex microsp heres were injected into the anterior chamber to demonstrate implant p atency. Light microscopy was used to study the tissue response to the implants and the pathways of aqueous flow. RESULTS: In general, the au thors found a granulomatous inflammatory response to the HA accompanie d by neovascularization into the implant and minimal fibrous encapsula tion of the reservoir. CONCLUSIONS: The use of HA as a suprascleral re servoir has several advantages, the major one being a theoretical incr ease in the functional lifetime of the implant.