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Nancy Brady, Marina Milenkovic, Anthony Lam; An Examination of the Effects of Evaporation on Antimicrobial Efficacy of Contact Lens Care Solutions. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5480.
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© ARVO (1962-2015); The Authors (2016-present)
Partial evaporation of contact lens care solutions, as can occur from failure to cap the contact lens case as directed, may result in loss of antimicrobial efficacy of the solution and lead to contact lens-related eye infections. This study evaluated the impact of partial evaporation on the antimicrobial efficacy of several contact lens care solutions when tested according to ISO 14729.
The solutions studied were - Investigational MPS-1: polyhexamethylene biguanide (PHMB) + poloxamer (PLX) and currently marketed Japan products MPS-2: polyquaternium (PQ1) + tetronic 1304 MPS-3: PHMB + poloxamine (PLA) and MPS-4: PHMB +PLX. Solutions were evaporated under a stream of air to 2x and 4x concentrations and challenged with Pseudomonas aeruginosa (ATCC 9027), Serratia marcescens (ATCC 13880), Staphylococcus aureus (ATCC 6538), Candida albicans (ATCC 10231) and Fusarium solani (ATCC 36031). The assay was performed according to the stand-alone test outlined in ISO 14729:2001/A.2010. The test solutions were evaluated at 4 hours and compared to the non-evaporated product. The solutions were assessed for their ability to meet the criteria of 3 log reduction of the bacteria and 1 log reduction of fungi at the minimum time interval.
After 4 hrs of inocula exposure, Investigational MPS-1 met criteria when non-evaporated and at the 2X and 4x evaporation level. MPS-2 failed to meet criteria when non-evaporated (for S. aureus and Candida) and also failed at the 2x and 4x levels (for S. marcescens, S. aureus, Candida and Fusarium). MPS-3 met criteria when non-evaporated and 2x level but failed criteria at 4x (for Candida). MPS-4 failed to meet criteria when non-evaporated (for S. aureus and Candida) and also failed criteria at the 2x and 4x (for S. marcescens, S. aureus and Candida).
The study demonstrates that, after partial evaporation up to 4X, modelling the potential error of not capping a lens case correctly, MPS solutions can lose significant disinfection activity. The solutions that failed to meet stand-alone criteria when non-evaporated showed more pronounced loss after evaporation. Of the solutions tested, only MPS-1 retained its full efficacy of stand-alone disinfection activity after being evaporated to a 4x level.
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