Impact of Cleaning Regimens in Silver-Impregnated and Hydrogen Peroxide Lens Cases

Abstract

Lens storage case hygiene practices are important for safe contact lens wear. However, the effectiveness of the manufacturer's direction for use and various cleaning regimens in reducing biofilm load is yet to be evaluated and compared. This in vitro study compared the effectiveness of several cleaning methods using silver-impregnated lens case and hydrogen peroxide disinfection systems. Biofilms of Pseudomonas aeruginosa 122 and Staphylococcus aureus ATCC 6538 were grown in silver-impregnated and hydrogen peroxide lens cases. After the establishment of the biofilms, the silver-impregnated case was subjected to one of four cleaning regimens: "manufacturer's directions for use--rinsed and recapped"; "rubbed, rinsed, and recapped"; "rubbed, rinsed, and air dried"; or "rubbed, rinsed, tissue wiped, and air dried." Hydrogen peroxide cases underwent one of two regimens: "manufacturer's directions for use--rinsed with saline and air dried" or "soaked in solution for 6 hrs." The level of residual bacteria was quantified. The efficacy of each cleaning regimen was then compared. Mechanical rubbing and wiping of silver-impregnated cases and soaking hydrogen peroxide cases in hydrogen peroxide were the most effective treatments for reducing biofilms. Once the silver-impregnated cases were rubbed, air drying or recapping the cases did not have any significant effect on the level of the biofilm. The level of initial biofilm formation of silver-impregnated cases was significantly lower than those of polypropylene lens cases (P<0.0001). Rubbing and rinsing with disinfecting solution and wiping with a tissue can be considered to be effective in removing biofilms from silver-impregnated lens cases. Resoaking the basket-type lens case in hydrogen peroxide between use was found to be effective in removing biofilms from these cases.