Antimicrobial Efficacy of Contact Lens Solutions Assessed by ISO Standards

Abstract

Microbial keratitis (MK) is an eye infection caused by opportunistic bacteria or fungi, which may lead to sight-threatening corneal ulcers. These microorganisms can be introduced to the eye via improper contact lens usage or hygiene, or ineffective multipurpose solutions (MPSs) to disinfect daily wear contact lenses. Thus, the patient’s choice and use of these MPSs is a known risk factor for the development of MK. It is then critical to determine the efficacy of popular MPSs against ubiquitous ocular microorganisms. Therefore, we compare the efficacy of nine major MPSs on the global market against four different microorganism species, and with four different common contact lenses. In accordance with International Standards Organization protocol 14729 and 18259, the microorganisms were inoculated into each MPS with and without contact lenses, and held for the manufacturer’s disinfection time, 24 h, and 7 days after challenge with Serratia marcescens or Fusarium spp. Plates were incubated for 2–7 days and plate counts were conducted to determine the number of surviving microorganisms. The majority of MPSs demonstrated significantly higher disinfection efficacies without contact lenses. Broadly, among the microorganisms tested, the OPTI-FREE products (Puremoist, Express, and Replenish) maintained the highest disinfection efficacies at the manufacturer’s stated disinfection time when paired with any contact lens, compared with other MPSs. These were followed closely by RevitaLens and renu Advanced. MPSs containing dual biocides polyquaternium-1 and myristamidopropyl dimethylamine possessed the highest disinfection efficacy against multiple ocular pathogens.

Reduction of disinfection efficacy of contact lens care products on the global market in the presence of contact lenses and cases

“…However, while this range of potential contamination activities are ever-present, it’s important that the CLC solutions commonly available to consumers are able to robustly disinfect lenses when used as directed, to otherwise protect patients against the micro-organisms that their lenses may come in contact with. Additionally, it is equally important that products are not only tested in the test tube stand-alone scenario, but also in the real-world common-use scenario involving contact lenses and cases, and that they maintain similar disinfection efficacy to the oft-reported stand-alone results 9 13. It has previously been shown that contact lenses themselves, as well as the contact lens cases packaged with CLCs, can take up biocide out of solution, thereby making any CLC less effective in this real-world situation 7 19…”

“…Both ISO 14729 (stand-alone tests) and ISO 18259 (with-lens tests) antimicrobial efficacy testing were performed. While ISO 14729 also includes testing for Candida albicans, Serratia marcescens, Pseudomonas aeruginosa and Staphylococcus aureus, commercially available products typically demonstrate a high degree of disinfection efficacy against most of these organisms with and without lenses present, although some products struggle to show with-lens disinfection efficacy against Candida 7 9. Therefore, of the ISO 14729 organisms, we chose the Fusarium spp as a highly challenging (and also common pathogenic organism causing MK)4 organism to differentiate between products.…”

“…As previously described,9 ISO 14729 testing was performed by inoculating 1.0×10 5 to 1.0 x 10 6 CFU/mL of the tested micro-organisms into test tubes containing 10 mL of the required CLC. Test tubes were made of compatible materials based on the biocides within the CLC (Grenier round bottom polystyrene tubes, Millipore Sigma #Z617776, Burlington, Massachusetts, USA).…”

“…As previously described,9 ISO 18259 was performed by aseptically removing contact lenses from the blister package and soaked in phosphate buffered saline for 18 hours. The lenses were briefly blotted on sterile gauze to remove excess solution, and placed in the matching manufacturer’s contact lens case concave side up.…”

“…Unfortunately, both Fusarium and Acanthamoeba pose unique challenges as difficult organisms to disinfect against. Bacterial pathogens which are the most common sources of MK are routinely highly susceptible to CLCs 7–9. However, Fusarium and Acanthamoeba stand out as highly differentiating, challenging micro-organisms against which not all products are highly effective.…”