The Influence Of Iol Water Content On Iol Calcification And Glistening Formation

Clinical evidence suggests a causal association between the water content in intraocular lenses (IOL) and the risk of IOL opacification. This study aims to investigate this association by examining a new IOL with a 7% water content for typical causes of IOL opacification. IOL calcification was evaluated using an in vitro electrophoresis model comparing two IOLs of varying water content. Glistening formation was analyzed using the accelerated ageing in vitro protocol and subsequently assessed according to the Miyata Scale.

Experimental in vitro laboratory investigation at the David J. Apple International Laboratory for Ocular Pathology, Department of Ophthalmology, University of Heidelberg, Germany.

To investigate IOL calcification, two IOL models of varying water content (CT Spheris 204, 25%, Zeiss and BSUV, 7%, Eyebright Medical Technology Inc.) and a control IOL (Clareon CNA0T0, 1,5%, Alcon) were exposed to aqueous solutions of 14 mM disodium hydrogen phosphate (Na₂HPO₄). IOL calcification was analyzed by light microscopy, Alizarin Red staining, von Kossa staining, scanning electron microscopy, energy dispersive x-ray spectroscopy, and transmission electron microscopy with electron diffraction. To investigate glistening formation, four BSUV IOLs underwent the accelerated ageing procedure. Subsequent glistening formation was counted as microvacuoles per square millimeter (MV/mm²) and subsequently graded according to the Miyata Scale.

IOLs with an increased water content were associated with increased IOL calcification. Semiquantitative analysis of IOL surfaces and IOL cross-sections showed signs of IOL calcification in CT Spheris IOLs (25% water content) after 5 hours of electrophoresis exposure, compared to BSUV IOLs (7% water content) after 15 hours of exposure to 14 mM Na₂HPO₄. The presence of IOL calcification was confirmed by all methods of analysis, while no IOL calcification was detected in the control IOLs. Analysis of glistening formation in the BSUV IOLs showed an average result of 1.8+0.9 MV/mm², corresponding to glistening grade 0 (< 50 MV/mm­²) on the Miyata Scale.

Our results demonstrate an association between IOL water content and IOL calcification risk, most importantly, that a decrease in IOL water content (7% rather than 25%), rather than frequently proposed hydrophobic surface properties, seems to reduce the risk of IOL calcification. Additionally, our study revealed an absence of glistening formation in the BSUV IOL, mitigating an additional cause of IOL opacification. Overall, these findings underscore the significance of considering IOL water content as a critical factor in the design and selection of intraocular lenses to minimize the risk of opacification and ensure long-term visual outcomes for patients undergoing cataract surgery.