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T. L. Adamus, F. Zhao, M. J. Coffey, M. S. Bergren; Concentrated Multi-Purpose Contact Lens Care Solutions and Biocidal Efficacy. Invest. Ophthalmol. Vis. Sci. 2007;48(13):781.
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Non-compliant lens care practices may increase the risk of bacterial or fungal infection in contact lens wearers. The purpose of this study was to determine if the biocidal efficacy of marketed multi-purpose lens care solutions (MPS) may be adversely affected when concentrated by evaporation, and whether any particular MPS may perform well under these extreme conditions.
Six MPS products currently on the market were selected for the study. Two out of the six products are based on polyquaternium-1(PQ)/myristamidopropyldimethylamine (MAPD) disinfection platform, and the remaining products are based on polyhexamethylene biguanide (PHMB) platform. The MPS products were concentrated by evaporation in a biological safety cabinet held at room temperature followed by ISO Stand-Alone biocidal testing. Two microorganisms Staphylococcus aureus and Fusarium solani were selected for the biocidal testing to represent the bacterial and fungal species, respectively. The "as is" marketed products were also tested in parallel as controls.
For activity against the bacteria Staphylococcus aureus, a significant downward trend was observed with increasing concentration in the PQ/MAPD based MPS products at both the four and six hour time points in the biocidal testing. The MPS products based on PHMB remained efficacious against Staphylococcus aureus under the same treatment. For activity against the fungi Fusarium solani, the downward trend was again observed with increasing concentration in the PQ/MAPD based MPS products at both the four and six hour time points. Thiswas also observed for some PHMB based MPS products with increased concentration. Overall, only two PHMB based MPS products exhibited no reduction in biocidal efficacy against the two microorganisms when concentrated by evaporation.
Evaporation of MPS products may lead to reduced biocidal efficacy. PQ/MAPD based MPS products appeared to be more sensitive to these conditions than PHMB based MPS products. In general, the data suggest that contact lens wearers should not leave used or fresh MPS solutions in open lens cases or other open containers.
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