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Over the past decades medicine evolved continuously, which can clearly be seen in the rising average of life expectancy. But as the population gets older and older the number of old-age diseases increases. Cataract (cataracta senilis) is such an old-age disease and worldwide the number one reason for blindness. Cataract is a tanning of the natural lens severely affecting vision. Up to date explanation of the natural eye lens and its replacement by a polymeric intraocular lens (IOL) is the only way to treat cataract. After implantation of an IOL most of the patients do not achieve optimum vision. Reasons for this suboptimal result are individual effects e.g. wound healing. These effects are not fully predictable. Most of the patients have to wear viewing aids. Approximately 80% of all patients are in a range of ± 1 diopter around the optimum vision.
Our aim is to supply polymers which enable post-operative tuning of the refractive properties of the implanted IOL made of these new polymers in order to compensate for all remaining imperfections. These polymers are based on a poly methacrylate backbone and incorporate coumarin, stilbene and chalcone derivatives as side groups which can undergo a [2π+2π] - dimerization reaction. Through dimerization the conjugated π-electron system is decreased. As a direct consequence the molecules polarizability and relative permittivity are also affected. A closer look at the theory of velocity of light shows the direct relation of the refractive index n and the molecules relative permittivity.
In the presented work various polymers containing coumarins, stilbenes and chalcones were successfully synthesized and photo chemically characterized. These polymers show significant changes in refractive index upon irradiation of up to 3 diopters. Selected polymers were used to manufacture polymeric plates which were processed to prototypes. These prototypes could be machined by standard operating procedures used in the industry.
The second working package was to investigate new polymeric materials for high refractive index materials used for phacic intraocular lenses (PIOL). PIOL´s are used as an additional support in ophthalmic surgery. PIOL´s are very thin (0.1 mm in thickness) and have to be highly refractive. The desired refractive index should be bigger than n = 1.60. As a specialty the polymer should simultaneously absorb in the UV region and act as an UV absorber without adding one.
Two coumarin derivatives were therefore successfully synthesized. Methacrylate based polymers with these new coumarin derivatives showed refractive indices of n = 1.61. Furthermore these molecules absorb in the UV region enabling them to act as an UV absorber. In contradiction to previously synthesized polymers containing coumarin in the side chain of the polymer these molecules do not dimerize under irradiation.