Einfluss molekularer Strukturen auf die Entstehung von Glistening in hydrophoben Polymeren
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Date
2025-10-21
Authors
Publisher
Philipps-Universität Marburg
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Abstract
The phenomenon of glistening in lenses was first documented 40 years ago and observed as decreased optical quality.[1] Nowadays, we know that glistening occurs mainly in hydrophobic intraocular lenses (IOLs) in the presence of water resulting in scattering effects at the interface of the formed microvacuoles (MVs).[2] Up to this date, questions around the formation mechanism remained. Current methods to enhance the life span and slow down glistening effect, are based on admixing of hydrophilic polymer components. However, this approach exhibits the problem that more water content is included, resulting in a higher degree of swelling and hence poorer refractive index of the material. In this study, the glistening formation is investigated systematically for the first time identifying two interrelated determinants by using established in vitro tests and a customized measurement system. The latter enables three-dimensional localization of glistening formation sides and the quantification of microvacuoles (MVs/mm3) independent of sample shape and thickness. The system’s high resolution is capable of detecting particles up to a diameter of 1.5 µm. Additionally, it combines temporal analysis facilitating detailed observation of microvacuoles formation. As a first result, contaminations like solid particles, dust, solvent residues and encapsulated gases were identified as promoters of the glistening formation. It could be shown that by introducing additional steps to the synthetic process - filtering and homogenizing monomer mixtures, as well as intensive drying processes of the polymers - prevented contaminations in the end material, and hence extended the life durability of lenses. Second, using the measurement setup on the adjusted sample preparation enables an in-depth analysis of glistening, which is identified to be ascribed solely to the polymer composition. Based on this approach, a reduction in the microvacuole density was found with increasing amount of cross-linker in the hydrophobic acrylic systems ethylene glycol phenyl ether acrylate (EGPEA) and ethylene glycol phenyl ether methacrylate (EGPEMA). By using five different cross-linkers, an innovative approach to preventing glistening was developed, resulting in fully glistening-free and vacuole-free materials. Both the degree of cross-linking and the choice of cross-linker influence the optical and mechanical properties essential for ophthalmology due to the molecular structure and the associated interactions between the polymer chains. The method for obtaining glistening-free polymers using cross-linkers is successful even with the same degree of cross-linking if additional copolymers are used to lower the glass transition temperature. These copolymers are necessary to reduce the hardness and the glass transition temperature, which exceed the required values for ophthalmological use due to the high amount of cross-linker. The use of short-chain aliphatic acrylic monomers like butyl acrylate has proven to be particularly effective. Based on the findings, the production routes of high-index, purely hydrophobic, glistening-free IOL materials have been established that can be tailored to the desired optical and mechanical requirements.
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Dates
Created: 2025Issued: 2025-10-21Updated: 2025-10-21
Faculty
Fachbereich Chemie
Language
ger
Data types
DoctoralThesis
Keywords
Polymerisationphysical chemistryChemistry, Glistening, Intraocular lens, IOL, Material ScienceIOLMaterialwissenschaften, physikalische Chemie, VernetzerBiomaterialien, Kataraktpolymerization, Polymere, Microvacuole, Biomaterials, cataractCross-linker
DFG-subjects
PolymerIntraokularlinseOphthalmologiehydrophobe Polymere, MethacrylateGlistening, IOLMikrovakuolenVernetzerAcrylate
DDC-Numbers
540
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Heidary, Nima: Einfluss molekularer Strukturen auf die Entstehung von Glistening in hydrophoben Polymeren. : Philipps-Universität Marburg 2025-10-21. DOI: https://doi.org/10.17192/z2025.0532.