A Preservative-and-Fluorescein Interaction Model for Benign Multipurpose Solution–Associated Transient Corneal Hyperfluorescence

Abstract

Multipurpose contact lens solution (MPS)/preservative-associated transient corneal hyperfluorescence has been suggested to represent corneal injury. To determine the validity of this assumption, the molecular-level interactions of common disinfectants in soft contact lens MPS and the corneal epithelium using an in vitro model were assessed. A liposome-based model of the corneal epithelial surface was developed and used to assess the interactions of polyhexamethylene biguanide (PHMB), polyquaternium-1 (PQ-1), and fluorescein with membrane components and the effects of PHMB and PQ-1 on membrane integrity. The fluorescence anisotropy (a measure of interactions between molecules) was determined. Liposome integrity was assessed by measuring the liposome melting point temperature. Free fluorescein did not associate with the liposome (P>0.4). Both fluorescein-tagged PHMB and PQ-1 associated with liposomes (P<0.002 and P≤0.01, respectively); however, only PHMB induced free fluorescein association with membrane components. At physiological temperature, no significant shift in the melting point temperature was observed when liposomes were exposed to PHMB from 0 to 100 ppm (P>0.05). In contrast, exposure of >7 ppm PQ-1 disrupted the liposomes. Based on this study, PHMB-to-liposome bilayer interaction is nondestructive, even at concentrations 100 times higher than found in commercially available MPS products. In contrast, PQ-1-to-liposome bilayer interaction led to liposome disruption. This study presents molecular-level evidence to support that preservative-associated transient corneal hyperfluorescence is a benign transient phenomenon and its evaluation clinically may be an ambiguous strategy for determining biocompatibility and cell surface integrity.