Contact Lens Case With Silver Shows Reduced Microbial Presence in Daily Use

A passive method involving contact lens storage cases inhospitable to bacteria may be a nearly effortless way to help prevent ocular infection, according to research presented at the American Academy of Optometry 2021 in Boston, November 3-6, 2021.  Investigators at the University of New South Wales in Sydney, Australia, led by Parthasarathi Kalaiselvan, M Optom, examined whether the rate and level of potentially harmful microbes was reduced when habitual contact lens wearers used storage cases impregnated with silver.

Silver’s antimicrobial properties have been known for hundreds of years and the element was widely used before the introduction of antibiotics. Theories presented during the late 1900s and early 2000s propose that when silver becomes moist and releases ions, it can affect cells such as a bacterium by decreasing the expression of proteins involved with energy production, or by damaging the microbe’s DNA. Previous research has demonstrated lens cases impregnated with silver can reduce the amount of bacterial contamination and biofilm, but few of the analyses until now have assessed this effect during typical everyday use.

The current study reveals “a >65% reduction in the average numbers of microbes in silver-impregnated cases (1.5±0.9 log CFU/case) compared with nonsilver cases (2.0±1.8 log CFU/case).”

Microbial presence in standard contact lens cases occurred at a rate of 91%, although in silver-impregnated cases, the proportion was 73%, significantly lower (P =.0009). In standard cases, gram-positive bacterial contamination occurred at a frequency of 72%, compared with silver-containing cases at 47% (P =.0003). For gram-negative bacteria, this frequency was 44% in standard lens cases, vs 30% for cases with silver (P =.04). Also, fungi were present at a rate of 25% in the nonsilver cases, and 7% in silver-impregnated cases (P =.0005).

This single-center, single-masked study included 12 participants (mean age 32±10 years, 67% women), who were randomized to use a standard contact lens case, or a case containing silver for 3 months, and crossed-over to use the other case for 3 additional months. All wore weekly or monthly replacement silicone hydrogel lenses, and stored lenses in a multipurpose solution with hyaluronic acid, a natural lubricant typically found in connective tissue, skin, and the eye; and polyhexamethylene biguanide (PHMB), an antimicrobial polymer. Lens cases were collected and cultured at 1-, 3-, 4-, and 6-month follow-up appointments.

The prospective study’s sample size was small; 10 participants completed the full protocol. However, it is one of the first real-world investigations to explore this straightforward method to support prevention of infection.

Disclosures: This study was funded in part by CooperVision, Inc. Please see the original reference for a full list of disclosures.

Reference

Kalaiselvan P, Vijay AK, George M, Willcox M. Antimicrobial efficacy of silver contact lens cases used in conjunction with a multipurpose disinfecting solution containing hyaluronic acid. Poster presented at the American Academy of Optometry 2021 meeting; November 3-6, 2021; Boston. Board #25.