Microbial keratitis (MK) is one of the most devastating complications of contact lens wear and can lead to blindness, yet the incidence and associated risks of this condition have remained consistent over three decades (Szczotka-Flynn et al, 2021). MK is a result of infections by several common ocular pathogens. Acanthamoeba keratitis is one of the most challenging ocular infections to treat, because Acanthamoeba cysts are extremely resistant to biocidal activity (Walters et al, 2022).
Impact of Care Systems
It is important to understand how contact lens care systems help protect against common pathogens. Preservative-free care systems historically demonstrate greater disinfection efficacy than multipurpose solutions, which depend on biocides and preservatives (Retuerto et al, 2012; Kilvington and Lam, 2013; Szczotka-Flynn et al, 2009). Hydrogen peroxide or povidone iodine are the main disinfecting agents in preservative-free systems.
A study directly compared the disinfection efficacy of three preservative-free disinfection systems against bacteria (Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens), fungi (Candida albicans and Fusarium keratoplasticum), and Acanthamoeba trophozoites and cysts (Yasir et al, 2021). This included two one-step hydrogen peroxide-based systems and one two-step povidone iodine-based preservative-free system. Individual challenges were prepared according to the International Standards Organization (ISO) method 14729 (Walters et al, 2022). Bacterial challenges must exhibit at least a 3-log reduction and fungal challenges must demonstrate at least a 1-log reduction to meet the ISO criteria (Acanthamoeba is not included in ISO 14729). For the ISO panel, all three of the preservative-free care solutions tested met and exceeded these primary criteria with no differences between solutions.
However, differences were noted when tested against Acanthamoeba and in the presence of contact lenses. Differences between both care systems became evident when a modified stand-alone procedure was applied to the trophozoites and cysts of four different Acanthamoeba strains; all resulted in the povidone iodine-based solution delivering significantly less disinfection efficacy than the hydrogen peroxide-based care systems. This was particularly evident with the cyst experiments, as the povidone iodine-based solution underperformed the hydrogen peroxide-based care systems in all four Acanthamoeba strains tested.
The hydrogen peroxide-based solutions maintained comparable efficacies in the absence or presence of lenses for Acanthamoeba and Fusarium, while the efficacy of the povidone iodine-based solution was affected by the addition of contact lenses.
In Summary
Preservative-free disinfection systems using hydrogen peroxide or povidone iodine are systems for disinfection of contact lenses against pathogens that cause MK. This study shows that hydrogen peroxide-based care systems are more efficacious than povidone iodine-based systems against both Acanthamoeba trophozoites and cysts. CLS
References
- Szczotka-Flynn LB, Shovlin JP, Schnider CM, et al. American Academy of Optometry Microbial Keratitis Think Tank. Optom Vis Sci. 2021 Mar 1;98:182-198.
- Walters R, Campolo A, Miller E, et al. Differential Antimicrobial Efficacy of Preservative-Free Contact Lens Disinfection Systems against Common Ocular Pathogens. Microbiol Spectr. 2022 Feb 23;10:e0213821.
- Retuerto MA, Szczotka-Flynn L, Ho D, Mukherjee P, Ghannoum MA. Efficacy of care solutions against contact lens-associated Fusarium biofilms. Optom Vis Sci. 2012 Apr;89:382-391.
- Kilvington S, Lam A. Development of standardized methods for assessing biocidal efficacy of contact lens care solutions against Acanthamoeba trophozoites and cysts. Invest Ophthalmol Vis Sci. 2013 Jul 5;54:4527-4537.
- Szczotka-Flynn LB, Imamura Y, Chandra J, et al. Increased resistance of contact lens-related bacterial biofilms to antimicrobial activity of soft contact lens care solutions. Cornea. 2009 Sep;28:918-926.
- Yasir M, Kumar Vijay A, Willcox M. Antiviral effect of multipurpose contact lens disinfecting solutions against coronavirus. Cont Lens Anterior Eye. 2021 Aug 27:101513. [Online ahead of print]