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M.L. Ajello, M. George, M. Mowrey–Mckee; A Saline Challenge of a Silver–Impregnated Lens Case . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2411.
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Lens case contamination is a well–documented occurrence for patients who wear contact lenses despite the efficacy of currently marketed lens disinfectants. Several microorganisms have a propensity to attach to surfaces and may become more tolerant of disinfection than planktonic (free–swimming) cells. Additionally, non–compliance with disinfection regimens occasionally occurs wherein patients store their lenses in saline or in tap water. In these circumstances, the ability of the lens case to inhibit contamination on its own takes on additional importance. This study examined the efficacy of the PRO–GUARD silver–impregnated lens case in the absence of disinfecting solution against saline suspensions of known lens case contaminants. A low inoculum level was employed to more closely mimic real world exposure conditions. Performance of the PRO–GUARD case versus currently available lens cases was assessed.
Lens case bowls were challenged with 103 microorganism suspensions of Pseudomonas, Serratia, and Citrobacter strains. After twenty–four hours incubation at room temperature, aliquots of inocula were removed and spread plated onto appropriate growth media. Surviving colonies were counted and microorganism log drop values from initial challenge inocula were determined.
The PRO–GUARD case demonstrated kill of Pseudomonas and Citrobacter after 24 hours exposure at room temperature. Bausch and Lomb® (ReNu®) and Complete® cases showed replication of these microorganisms (growth) after 24 hours. Opti–Free® cases demonstrated growth of Pseudomonas and stasis against Citrobacter. All lens cases demonstrated stasis against Serratia though the PRO–GUARD cases had a statistically significantly lower number of recoverable colonies than competitor cases.
The PRO–GUARD silver–impregnated lens case was developed in an effort to provide enhanced safety for patients by reducing potential lens case contamination between and after contact lens disinfection. In all challenges, the PRO–GUARD case had a statistically significantly lower number of recovered microorganisms than all competitor cases and shows promise as an added benefit to the contact lens care system.
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