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C. H. Powell, S. W. Huth, L. D. Hoong, K. Ambrus; Susceptibilities of Various Contact Lens Multipurpose Solutions to Efficacy Diminution When Partially Evaporated. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5367.
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© ARVO (1962-2015); The Authors (2016-present)
Recent regional episodes of high incidence of Fusarium-related mycokeratitis implicating a particular commercial multipurpose solution (MPS) have been reported as ostensibly emanating from evaporation phenomena associated with product misuse. Subjecting the implicated product (ReNu® with MoistureLocTM, no longer marketed) to controlled partial evaporation showed that the product concentrate could support Fusarium solani viability. Upon confirmation of this possible etiological link, other products were tested to determine ruggedness of antimicrobial activity toward partial evaporation. Several marketed MPS products were compared to assess relative efficacy retention in an evaporation model employing standard test organisms and procedures.
Stand-alone disinfection efficacy testing (per FDA/ISO Guidelines) was performed on products that had been evaporated to various levels. Products were evaporated to a "4X" concentration using a stream of air. Portions of the 4X concentrate were diluted to 2X and 1X (the original product concentration), and the different evaporation-level solutions were tested for antimicrobial activity against the FDA/ISO stand-alone panel.
The kill-rate data for various products were plotted against the degree of evaporation (represented by 1X, 2X and 4X product concentrations). The data for RENU® with MoistureLocTM (the positive control) showed total loss of activity against Fusarium solani and Candida albicans, even for the 2X concentrate.However, some other products, particularly all the OPTI-FREE® brand MPS products tested, also showed weakness in this model toward some organisms, relative to the PHMB-containing products. Particularly, the OPTI-FREE® and Opti-One® brand products showed substantial reduction in activity toward S. marcescens, S. aureus and/or C. albicans upon partial evaporation.
No currently marketed MPS product was found to lose antimicrobial efficacy at the level of ReNu® with MoistureLocTM in the partial-evaporation model. However, among the various MPS products tested, there are differences in antimicrobial performance as a function of degree of evaporation that may indicate a higher patient risk for some products in this misuse scenario, particulary for the OPTI-FREE® and Opti-One® brands. However, PHMB based products are indicated to be quite rugged with respect to partial evaporation effects.
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