Abstract
Purpose::
The purpose of this study was to evaluate the effect of storing lenses in Multi-Purpose Solutions (MPS) on antimicrobial activity.
Methods::
Three ml of each solution tested was added to the side-by-side screw cap lens cases. The MPS solutions tested contained POLYQUAD® biocide (OPTI-FREE® EXPRESS® and OPTI-FREE® REPLENISH® Multi-Purpose Disinfecting Solutions (Alcon), Alexidine* (ReNu with MoistureLoc* [previously marketed by B&L], and PHMB (Aquify* [Ciba], Complete Moisture Plus* [AMO], and ReNu MultiPlus* [B&L]) MPS solutions (* = trademarks of other companies). ACUVUE* 2 (etafilcon A) traditional soft lenses were stored in six MPS Solutions in the solution manufacturer’s lens cases for 2, 4, 6, 24 and/or 48 hours, and 7 days. Following storage, the lenses were removed from the solutions and "spent" solutions were tested for antimicrobial activity. The "spent" solutions were inoculated to contain 1 X 106 CFU/ml of Fusarium solani and Pseudomonas aeruginosa and sampled for survivors after a 4-hour disinfection time using neutralized culture media for appropriate incubation times. Similarly, a chemical analysis for preservative uptake was conducted after lens storage using a HPLC or UV spectroscopic method, as appropriate.
Results::
Reduced fungicidal activity was observed for "spent" solutions preserved with Alexidine and PHMB in as little as 2 hours. All solutions maintained bactericidal activity through 24 hours; however, two of the product’s "spent" solutions showed markedly decreased bactericidal activity after storage of lenses for 7 days. The levels of biocides remaining in the "spent" solution were also reduced with increasing lens storage. "Spent" solutions of OPTI-FREE® EXPRESS® and OPTI-FREE® REPLENISH® products were not significantly affected by storing lenses, and the antimicrobial activity against both F. solani and P. aeruginosa remained constant. The levels of the POLYQUAD biocide remained stable in the "spent" solutions during storage.
Conclusions::
The results suggest that the antimicrobial efficacy of MPS Solutions may be affected by lens storage time and by reusing MPS Solutions.
Keywords: contact lens • Pseudomonas • fungal disease