The impact of silicone hydrogel-solution combinations on corneal epithelial cells

Silicone hydrogel (SiHy) contact lenses were introduced on the market over 10 years ago, and several multipurpose solutions (MPS) have since been developed for their cleaning and disinfection. Depending on the combination of lens and solution, clinical and retrospective studies have shown that different combinations may be more biocompatible than others. In vivo, sodium fluorescein is used to assess the corneal response, whereas in vitro studies typically investigate MPS toxicity by incubating diluted MPS with cells. This difference between in vivo and in vitro measurements makes it difficult to gain a better understanding of the biocompatibility of SiHy-solution combinations. This review discusses the recent progress in characterizing the interactions between sodium fluorescein and corneal epithelial cells and in vitro MPS cytotoxicity using solution on both monolayer and stratified epithelial models. As interactions between MPS and contact lens materials lead to uptake and release of various solution components, in vitro models that take into account the effect of lens material are also presented. With the improvement of advanced characterization methods and new in vitro models, we are moving in the right direction, but more effort is required to fully elucidate the interactions between contact lens, disinfecting solution, and the cornea.