Stability of crofilcon and polymacon (clear andtinted) contact lenses after microwave irradiation

Abstract

Several authors investigated the use of standard microwave ovens as an alternative method for soft contact lens disinfection. However, none of these studies tested whether or not repeated exposure to microwave irradiation could alter the properties of crofilcon A or tinted polymacon soft contact lenses. The purpose of this study was to evaluate the effects of microwave disinfection on optical properties of unworn lenses from group 1 of the FDA material classification. Afocal lenses including clear and aqua Hydron Z6 and CSI DW were used. Each lens was placed in a Ciba AOSept case, filled with unpreserved saline. All the lenses were disinfected together for 120s in a standard microwave oven with a rotating plate. Lens variables (back vertex power, back optic zone radius (BOZR) and water content) were measured at baseline and after 30, 60 and 90 cycles of microwave disinfection. The results indicated that there were no statistically or clinically significant changes in the refractive power and BOZR after 90 disinfection cycles. But our results showed a statistically significant change in water content for every lens type (range −0.1% to +0.9%). However, these differences are within experimental error and are not clinically significant. Microwave disinfection is a feasible alternative to current disinfection methods in group 1 lenses at least when its effects on optical properties are considered. Further studies on the effects of microwave irradiation on worn soft lenses are needed.