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C. Lakkis, F. Anastasopoulos, C. Terry, R. Borazjani; Time Course of the Development of Contact Lens Case and Contact Lens Contamination. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6352.
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This study investigated the time course of development of case and contact lens (CL) contamination during daily wear of silicone hydrogel CLs.
A prospective, randomised, masked study was conducted. 73 subjects were fitted with senofilcon A CLs, randomly assigned to use 2 care systems [solution A (preservatives: polyquaternium-1 and MAPD) and solution B (preservative: PHMB)] on a contralateral basis and to return at 1 of 3 follow-up times: 7 ± 2 (Group 1), 14 ± 3 (Group 2) or 30 ± 5 (Group 3) days. Cases and CLs were cultured for bacterial contamination and levels of contamination (colony forming units (CFU)/ml) were graded on a 5-point scale (0 (nil) = 0, 1 (trace) = 1-10, 2 (light) = 11-100, 3 (moderate) = 101-300 and 4 (heavy) = >300).
59% of cases and 34% of CLs were contaminated; however, there were no significant differences in contamination rates between the 3 follow-up groups (p>0.05). Group 1 cases showed significantly less moderate and heavy contamination compared to Groups 2 and 3 cases (p<0.05). CLs had significantly lower contamination levels than cases (p<0.05), with the majority of contaminated CLs showing only trace levels of contamination. 47% and 21% of cases were contaminated with gram-positive and gram-negative bacteria respectively, with no significant differences between follow-up groups and solution types (p>0.05). However, there was a trend towards reduced gram-positive contamination of solution A cases compared to solution B cases (p=0.10). 30% of CLs were contaminated with gram-positive bacteria and 5% with gram-negative bacteria. In Group 3, solution A disinfected CLs had significantly less gram-positive contamination than solution B disinfected CLs (p<0.05). Case and CL contamination levels were significantly correlated (rs=0.22, p<0.05).
CL cases become contaminated after 1 week of use; however, are more likely to show moderate to heavy contamination after 2 weeks use. CLs also become contaminated after 1 week of use, but this occurs less frequently and to a lesser degree than case contamination.
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