contact lens case reports
Searching for an Antimicrobial Contact Lens Case
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO

In a 1990 study titled "Inefficacy of Soft Contact Lens Disinfection Techniques in the Home Environment," we found that 42 percent of patients had culture-positive bacteria growing onto the inner

inner walls of their contact lens cases. Further studies showed that these bacteria were radically different from laboratory grown organisms. This discrepancy occurs because within the nutrient-deprived environment of the contact lens case, the bacteria undergo a series of complex survival strategies, one of which involves secreting a glycocalyxprotected biofilm (Figure 1) that renders the bacteria more resistant to currently available lens disinfection products.

Figure 1. Scanning electron micrograph of a bacterial biofilm within a contact lens case.

Preventing Biofilm Formation

To better address the issue of bacterial binding, Implemed Inc. in 1996 developed a novel plastic that dramatically reduces biofilm formation on the walls of contact lens cases and actually contributes to the lens disinfection process. The company accomplished this through its patented Oligon technology, which consists of platinum, silver and carbon molecules impregnated within the matrix of the case. These elements work in tandem to create an electrochemical battery, which is "switched on" when normal saline is added to the case. The silver, platinum and carbon interaction liberates antimicrobial silver ions, which diffuse into the saline to prevent biofilm formation and provide an electrochemical disinfection of the lens.

A Silver Bullet for Microbes

Silver ions have a long history of antimicrobial and antifungal applications dating back to ancient times when people made drinking vessels with metallic silver walls to disinfect the water. Today, doctors routinely use silver compounds on newborns and in burn units to prevent ocular infection. Recent studies have shown that electromagnetic silver ions are particularly strong antimicrobial agents for both Gram-negative and Gram-positive bacteria as well as for many fungi.

In a 1998 study at Pacific University, we challenged the prototype Oligon case with preservative-free saline against five microorganisms: Staphylococcus aureous, Pseudomonas aeruginosa, Serratia marcescens, Candida albicans and Fusarium solani. The results were encouraging in that the preservative-free system alone effectively eradicated many of the microorganisms, but its disinfection time wasn't fast enough to meet FDA requirements for stand-alone disinfection. Ultimately, the study showed that if patients used the antimicrobial case in conjunction with current preserved disinfection solutions, then the combination could provide a new level of safety for them.

Soon to Come

In the near future, CIBA Vision will release its new antimicrobial lens case based on a similar silver ion technology. We believe that this represents another giant step forward in improving the efficacy of contact lens disinfection in the hands of our often noncompliant patients.

To obtain references for this article, please visit www.clspectrum.com/references.asp and click on document #111.

Patrick Caroline is an associate professor of optometry at Pacific University and is an assistant professor of ophthalmology at the Oregon Health Sciences University. Mark André is director of contact lens services at the Oregon Health Sciences University and serves as an assistant professor of optometry at Pacific University.