Flexible Polyacrylate mit hohem Brechungsindex für ophthalmologische Anwendungen

The aim of this work was the development of a flexible, transparent and high refractive index (HRI) material intended for application in the field of intraocular lenses (IOL). When developing polymers for medical applications, there are a variety of physical, chemical and medical parameters to consider. A high-refraction lens material is the basic prerequisite for the production of very thin phakic intraocular lenses (PIOL). These PIOLs are being implanted into the eye in addition to the natural lens. This treatment option offers many patients an alternative to refractive corneal surgery and is a powerful treatment option for severe ametropia. In this work, a concept for polyacrylates was developed, which makes it possible to prepare polymers basically in silicowith a modularized synthesis concept (- so to speak on the modular principle -) by modifying the polymer side chains. On the basis of structure-property relationships, polymers that are optimized for their application in a "parameter-compromise analysis"can be designed. This concept requires the accordance of the experimental data and numerical calculations. The parameters refractive index, optical dispersion (ABBE number), glass transition temperature and mechanical properties (hardness, rigidity) were investigated primarily. A concept introduced in this work, here named "YOGA" (Y) concept, describes the attachment of different units in the side chains, so that a minimal shrinkage during polymerization is achieved. According to this concept, high refractive index polyacrylates have been synthesized which, in addition to well-polarizable aryl systems, furthermore possess siloxane modifications, alkyl modifications and other types of aryl systems in the side chain. 37 polyacrylates were developed, manufactured and characterized, of which twelve are polymers based on the YOGA concept. The polymers shown have refractive indices ranging from nD = 1,504 - 1,638, ABBE numbers ranging from νABBE = 21.1 - 55.8, and glass transition temperatures ranging from Tg = - 26°C - 81° C. The YOGA concept also permitted important surface properties (free surface energy) can be set. The parameter-compromise optimization produced a promising, transparent polymer with refractive index nD = 1.60, νABBE = 30, and Tg = 28 ° C. This polymer was processed into lens prototypes on a special precision lathe and its micromechanical properties were examined directly on the lens body by microindentation. The method of microindentation for the determination of mechanical characteristics is a suitable method for the direct examination of intraocular lenses. Here, the processed polymer is examined and not the blank from which later the intraocular lens is made. The results from the indentation experiments obtained here provide good approaches for the mechanical characterization of soft, thin materials. Microindentation shows a wide range of applications and is already a widely used method in polymer engineering as well as in biological and medical technical fields of interest.[90-93] The design principle established here has been successfully verified on a variety of polymers, including 13 new polymers not yet described in the literature. The YOGA principle also opens up the area of cast lenses (in mold fabrication), as polymerization shrinkage can be minimized. Last but not least, the microidentification was first applied to even very soft materials. Now it is possible to measure the micromechanical properties of intraocular lenses on the processed intraocular lens and not only, as before, the starting material without prior processing. In addition, the biocompatibility of the newly developed materials was tested in an animal model and the handling under operating conditions was also examined. Due to the outstanding properties of the new polymers, these materials have great potential in the development and manufacture of modern phakic intraocular lenses.