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Fiona Stapleton, Jaya Dantam, Hua Zhu, Jran Ozkan, Thomas Naduvilath, Thomas Varghese, Mark D. Willcox; Antimicrobial Activity Of Silver Impregnated Contact Lens Storage Cases During Use. Invest. Ophthalmol. Vis. Sci. 2012;53(14):71.
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Persistent microbial contamination of contact lens (CL) storage cases occurs in up to 90% of asymptomatic wearers and colonisation by pathogenic organisms is a risk factor for microbial keratitis and sterile infiltrates. Silver impregnated contact lens storage cases have been introduced to limit storage case contamination. While there is good in vitro evidence to support their enhanced microbial killing above non-silver cases, there are limited data on their use during wear. This study evaluated microbial contamination in silver impregnated contact lens storage cases.
Two prospective studies were conducted. Regular storage cases (CIBA VISION®, Atlanta, GA) in study I (n = 40) and silver-impregnated cases (MicroBlock®, CIBA VISION®, Atlanta, GA) in study II (n = 41) were used in conjunction with a AQuify® multipurpose disinfecting solution and Balafilcon A contact lenses. Cases were replaced monthly and collected at 1, 3 and 4 (for silver-impregnated cases only) months. At collection storage cases were sampled and cultured for microbial identification and enumeration.
The overall rate of microbial contamination for silver-impregnated and regular cases was 71% and 82% respectively. However, there was significantly (p<0.005) lower levels of microbes in silver-impregnated cases (an average of 0.4 x 102 CFU per well) compared to regular cases (an average of 1.1 x 104 CFU per well). In particular, silver-impregnated cases showed lower levels of Gram-negative bacteria (p=0.04), Gram-positive bacilli (p=0.03) and fungi (p=0.006).
More than 70% of the storage cases used in daily wear CL care for a month were contaminated irrespective of the types of cases. However, silver-impregnated cases were colonised by reduced levels of bacteria, particularly pathogenic environmental organisms such as Gram negative bacteria and fungi.
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