Efficacy of the Multipurpose Solution for Soft Contact Lenses

1. Efficacy of the Multipurpose Solution for Soft Contact Lenses Sindy S.Y. Lai, Pauline Cho, Maureen Boost The Hong Kong Polytechnic University Objective: To evaluate the disinfectant capacity of 4 multipurpose solutions (MPS) for soft contact lenses after exposure to different storage conditions. Solution-C just met the criteria for S. aureus after 2 months at RT, but failed when stored in other conditions. Solution-B failed to meet the FDA criteria against S. aureus even after 1 month. Solution-A maintained its disinfecting capacity against Ps. aeruginosa under different conditions over 3 months, but activity against C. albicans was markedly decreased, barely meeting the FDA criteria. The antibacterial capacity of the M-Case for Solution-A decreased after 3 months, better disinfecting capacity being achieved in a new untreated case. All solutions were effective against F. solani. Only storage at 4ºC significantly reduced the disinfectant capacity of solutions. Method:3 bottles of each of 4 brands of MPS Solutions A (withpolyhexanide), B (Alexidine), C(polyhexamethylene biguanide) and D (polyquaternium-10), were stored at 4ºC, at room temperature (RT), at 30ºC in a oven and in a water bath, and at RT exposed to sunlight over a 3-month period. Disinfectants were challenged monthly with Ps. aeruginosa, S. aureus, Candida albicans and Fusarium solani according to the FDA stand alone criteria to determine if efficacy decreased during storage. Disinfection in the MicroBlock Lens Case (M-Case) provided with Solution-A was compared with disinfection in an untreated case to determine if this case increased the antibacterial capacity of the solution. Results: Solution-D stored in all conditions met the FDA criteria against all organisms over the 3-month period. Keys FDA guideline for bacteria FDA guideline for fungi and yeast Conclusion: Efficacy of MPS was adversely affected by both time and environmental conditions. The antibacterial capacity of the M-Case decreased after 3 months, confirming the need for education of contact lens user to replace the lens case after 3 months. Recent cases of microbial keratitis caused by F. solani have been linked to MPS solutions. However, in this trial, all solutions were effective against the type strains of this organism over the three months period. Failure of the Solution-B and Solution-C to reach FDA criteria against S. aureus is of concern. This study was supported by a grant from The Hong Kong Polytechnic University.