Modification of intraocular lenses to reduce calcification

Shokri, Navid (2019) Modification of intraocular lenses to reduce calcification. (PhD thesis), Kingston University, .


Intraocular lenses (IOLs) are used to correct vision when an individual develops a cataract. However, post-operative conditions include calcification of the IOL and replacement with a new IOL. Initially a range of gas fluorinated and modified using plasma treatment PMMA discs were made and then characterised by Attenuated Total Reflectance Infra-Red (ATR-IR) Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDA), X-ray Photoelectron Spectroscopy (XPS) and Io Beam Analysis (IBA) before and after immersion in the Simulated Aqueous Humour Solution (SAHS). It was found that the samples modified with Poly Ethylene Glycol (PEG) silane showed increased contact angles on the surface and slower diffusion rates compared to the control samples. These samples also showed the greatest hindrance towards calcification after 62 weeks of immersion in SAHS. Analysis of the deposits was achieved using a novel imaging technique utilising ImageJ® software which enabled quantification of SEM data. Ion beam analysis was employed to examine which surface modification technique caused the least damage to the bulk of the polymer, and the gas fluorination method proved to be too harsh for Poly-Methyl Methacrylate (PMMA) even though the quantification showed deposits were hindered after immersion. Secondly two types of chemically modified PMMA discs were prepared, i) by acid hydrolysis followed by modification using fluorinated epoxide ii) using hydrazine mono hydrate followed by modification using fluorinated aldehyde. SEM-EDS was used to verify that the surface modification was successful. Both modifications showed evidence of fluorine, with the epoxide modification showing a more intense peak indicating a more successful fluorination. The contact angle of the epoxide modified samples was 110ө, 25ө higher than that of fluorinated aldehyde modification. The results of the immersion studies were quantified using ImageJ as used in the previous section, they were also corroborated by confocal microscopy for the first time through calculation of surface deposit volume. Analysis of the chemically modified discs after immersion indicated that fluorinated epoxide treated discs were more resistant to deposition. Additionally, four types of bulk fluorinated samples were made by copolymerising Methyl Methacrylate (MMA) and Hydroxy Ethyl Methacrylate (HEMA) with octafluoropentyl methacrylate or dodecafluoroheptyl methacrylate at different concentrations (10% and 20%). The samples made were characterised using ATR-IR and contact angle measurement. The results showed that the samples containing fluorinated alkyl methacrylate had a higher contact angle than the control samples (MMA/HEMA only). Post immersion, SEM-EDS quantification by ImageJ and confocal microscopy the fluorinated alkyl methacrylate samples showed approximately half the quantity of deposits as the control indicating that the bulk polymerisation using fluorinated alkyl methacrylate can reduce the opacification significantly. To summarise, the results of this study indicate that the modifications can be successful in reducing deposition and therefore have the potential to hinder calcification and reduce the incidence of post-operative surgery.

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