| More than 800,000 IOLs will be implanted in the U.S. this year to replace the natural lens of the eye following cataract surgery. Improved biomaterials and better basic understanding of IOL polymer properties will be important to the safe use of this major human prosthesis. The studies presented in this disseration involved several important areas of IOL materials research.; Because of inadequate fundamental data, the mechanical and chemical properties of polypropylene (PP) and polymethylmethacrylate (PMMA) monofilaments were compared to help resolve current controversies concerning their suitability as IOL loop materials. Ultraviolet stability, flexural stress cracking, and notch sensitivity were studied. Polypropylene was shown to be more susceptible to ultraviolet photo-oxidative degradation than PMMA. Accelerated photo-oxidation suggested an estimated intraocular lifetime of 27 years for PP. Surprisingly, for blue PP, the copper phthalocyanine colorant acts as an effective stabilizer yielding an estimated life of 357 years. Polymethylmethacrylate monofilaments exhibited very poor flexural stress crack behavior and much greater sensitivity to surface cracks than PP. Based on these studies, it was concluded that PP is a superior IOL loop material.; To minimize tissue damage which may occur by endothelium-IOL adhesive interactions during surgery, hydrophilic polymer graft-coatings on PMMA were prepared using (gamma)-irradiation on aqueous monomer solutions. Monomers were N-vinylpyrrolidone and hydroxyethylmethacrylate. Surfaces were characterized by contact angle/surface energy, tissue and cell adhesion, and rabbit implant biocompatibility. Graft-coatings exhibited low solid-water interfacial free energies. Large reductions in cornea endothelium adhesion and fibroblast cell adhesion were noted. Irradiation polymerization exhibited a remarkable dose rate dependence. Surface modified PMMA implants showed excellent biocompatibility.; Polymethylmethacrylate compositions containing natural and synthetic ultraviolet absorbing additives were evaluated for use in UV-filtering IOLs. Although carotene, PABA, tetracycline, and retinal provided effective filtration, benzotriazole compounds appeared most promising. A rabbit anterior chamber injection test was developed to demonstrate additive biocompatibility.; An engineering thermoplastic, bisphenol-A polycarbonate (PC), was evaluated as a promising new IOL polymer and displayed good implant biocompatibility.; These studies have provided new fundamental data which can be important for future development of improved ocular implant biomaterials. |
