Efficacy of Disinfection during Long-Term Storage of Contact Lenses

1. Pauline Cho1, Maureen Boost2, Angel Lee2. 1. School of Optometry; 2. Dept of Health Technology & Informatics; The Hong Kong Polytechnic University, Hong Kong SAR, China Introduction Some contact lens (CL) patients only wear their CL for sporting or social occasions. It is suggested that CL may be safely used in such a way if they are cleaned, disinfected, and left to soak in a multipurpose solution (MPS) for up to 30 days without needing to repeat the disinfection process before use, though no published work has confirmed this. Recent increases in CL-associated keratitis suggest evaluation of CL routines is needed. Efficacy of Disinfection during Long-Term Storage of Contact Lenses Aims & Objectives To determine if lenses worn by CL wearers would be effectively disinfected and remain free of contaminants over a 30 day period To test log term disinfecting efficacy against CL contaminated with ocular pathogens To compare efficacy of commercial MPS solutions Methods Disinfection of regular contaminants. Eight volunteers wore a new pair of CL for one week. Their lenses were removed in the laboratory, cleaned by rubbing with MPS ‘A’ and placed in a new lens case containing MPS A. The MPS was sampled for contamination after 4 h and then every three days for 40 days. 0.1ml was extracted aseptically and diluted with 0.9ml Dey-Engley broth. 0.1 ml was cultured on blood agar and incubated for 48 h. The process was repeated 3 times for each subject using a new pair of CLs and MPS solutions B,C & D. Disinfection of artificially contaminated CL. CLs were immersed in a broth culture of 1000 CFU/ml of an ocular pathogen (Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, Escherichia coli or Candida albicans) and 1% serum albumen for one hour. CLs were cleaned, stored and sampled as above. Sixteen CLs were contaminated with each pathogen and four were tested against each of the MPS. MPS used were OPTIFREE Express (Alcon), COMPLETE Moisture Plus (AMO), ReNu with MoisureLoc (Bausch & Lomb) and Solo-care Aqua (Ciba Vision). Results After 4h, all MPS had achieved disinfection and no organisms were isolated from the disinfecting solutions of the CLs of either volunteers or artificially-contaminated lenses. Over the 30-day sampling period, samples yielded no growth. A few coagulase-negative staphylococci (CNS) were isolated in the final ten days. Conclusions Storage of cleaned CL in MPS for up to 30 days may be considered safe as both normal flora and ocular pathogens were inhibited by all MPS tested for this period. However, future study is required with lenses worn for longer period of time. CNS isolated in the latter stage of the trial may have been introduced during sampling and survived due to reduced disinfecting capacity. CLs were cleaned by rubbing which reduces organism load. Practitioners should remind infrequent wearers to rub lenses before storage and re-disinfect if they are stored for longer then 30 days. This work was supported by a Departmental Grant of the Dept of Health Technology & Informatics, The Hong Kong Polytechnic University.