The development of in vitro biocompatibility tests for the evaluation of intraocular biomaterials

Recent developments in ocular implant technology require the in vitro evaluation of ocular compatibility in early stage development programs. This requires an understanding and appreciation of the biological interactions which occur in the ocular environment and their relevance with respect to the clinical complications associated with surgical implantation of devices. This paper describes the development of a series of clinically reflective in vitro assays for assessing the potential ocular compatibility of novel intraocular lens materials. Staphylococcus epidermidis attachment, fibrinogen adsorption, mouse embryo fibroblast 3T3 adhesion and proliferation, primary rabbit lens cell adhesion, human peripheral blood macrophage adhesion and granulocyte activation tests were employed to evaluate two widely used intraocular biomaterials poly(methyl methacrylate) (PMMA) and silicone, and a novel biomimetic phosphorylcholine-based coating (PC). The performance of these materials in the in vitro assays was compared to their ability to reduce postoperative inflammation in vivo in a rabbit model. The results demonstrated that the in vitro assays described here are predictive of in vivo ocular compatibility. These assays offer a more relevant means of assessing the ocular compatibility of biomaterials than those presently required by the authorities for regulatory approval of medical devices and implants.