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R. Jain; Propensity of Hydrophilic Materials to Calcify: Material vs. Processing. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5433.
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© ARVO (1962-2015); The Authors (2016-present)
A previous study using subcutaneous implantation of hydrophilic acrylic intraocular lenses (IOLs) as a model for IOL calcification showed that 6 of 6 brands of commercially available IOLs demonstrated varying degrees of calcification (ARVO 2006). However, all hydrophilic IOLs are not alike, varying for example in water content and material processing. Calcification could be due to the inherent properties of the hydrophilic material, or to the processing of that material into an IOL. This study uses a rabbit model to assess minimally processed hydrophilic acrylic optical blanks with similar water contents for their propensity to calcify.
Biomaterials included CI26% Clear Standard UV (Contamac, Saffron Welden, Essex, UK), Benz IOL 25UV, and BenzFlex 26 (Benz Research and Development Corporation, Sarasota, FL) as well as a USP negative control, high density polyethylene. Optical blanks were lathed, hydrated and sterilized according to manufacturers’ guidelines to eliminate variance between samples due to surface processing. Eight disks, each 5.5 mm diameter and 1 mm thickness, were implanted subcutaneously in four New Zealand White (NZW) rabbits (Buchen et. al., JCRS 2001) for 70+2 days. Upon explantation, half of the specimens in each group were subjected to histological analysis and the other half, to scanning electron microscopy (SEM; surface morphology) and energy dispersive spectroscopy (EDX; elemental composition) at three representative sites per sample.
All of the hydrophilic materials demonstrated signs of calcification. There were no signs of calcification in the negative control. Signs of material degradation and pitting were exhibited in 50% of the Benz IOL 25UV and BenzFlex 26 samples, and in 25% of the CI26% Clear Standard UV samples. Calcification was confirmed by the presence of distinct calcium and phosphorus peaks in the EDX analysis.
In the current study, the three types of hydrophilic materials used to manufacture IOLs demonstrated evident signs of calcification. Processing of the hydrophilic acrylic materials was minimal. This suggests that hydrophilic acrylic materials have an inherent tendency to calcify. This tendency may be enhanced with the additional processing necessary to manufacture IOLs.
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