TO AVOID ocular adverse events—including corneal infiltrative events (CIEs) and microbial keratitis (MK)—proper contact lens (CL) care and hygiene are pertinent (Waghmare and Jeria, 2022; Maier et al, 2022; Ho et al, 2021). MK may be classified as a form of CIE, characterized by an active infectious process that requires antimicrobial treatment (Maier et al, 2022; Steele and Szczotka-Flynn, 2017; Stapleton et al, 2021). MK is categorized as clinically severe keratitis when antimicrobial treatment is required or nonsevere keratitis when no medical treatment is required (Maier et al, 2022; Jones et al, 2023; Steele and Szczotka-Flynn, 2017). Contact lens wear accounts for approximately 52% to 65% of newly diagnosed MK cases (Maier et al, 2022).
The frequency of MK occurrence could be influenced by the CL material, lens design, and type of care solution used (Waghmare and Jeria, 2022; Maier et al, 2022; Wu et al, 2015). Modifiable risk factors include planned replacement CL wear, the utilization of multipurpose CL solutions (MPSs), CL storage case overuse, smoking, and elevated eyelid bioburden and microbial colonization (Waghmare and Jeria, 2022; Ho et al, 2021; Jones et al, 2023).
Sleeping in CLs is the most significant risk factor for MK, and poor hygiene is the greatest risk factor for infectious MK due to CLs (Waghmare and Jeria, 2022; Maier et al, 2022; Jones et al, 2023). Nonadherence to recommended replacement schedules can compromise both CL performance and safety (Jones et al, 2023). This is particularly concerning for daily disposable lens wearers, as it can lead to decreased comfort and suboptimal vision (Jones et al, 2023). Other behaviors that increase the risk of MK include topping off disinfecting solution, infrequent cleaning and replacement of CL cases, and exposing lenses to tap water (Jones et al, 2023).
One study evaluated the disinfection effectiveness of 6 MPSs and a single hydrogen peroxide solution (HPS) comparator against 3 organisms associated with CL case-related CIEs (Corwin-Buell et al, 2025). The challenge organisms used for standalone testing due to their involvement with contaminated CL case CIEs were Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia. Each organism was cultured, harvested, and adapted using a spectrophotometer and Dulbecco’s Phosphate Buffered Saline with 0.05% mass/volume polysorbate 80.
In this study, using the International Organization for Standardization (ISO) 14729 standalone test protocol with organic soil, the solutions were tested against commonly isolated Gram-negative organisms associated with CL case-related CIEs. Disinfection efficacy was reported as the mean log reduction for each organism and the overall disinfection performance across all 3 organisms in a post-hoc analysis.
Various MPSs were found to have different antimicrobial abilities. Standalone testing against the challenge organisms demonstrated that polyaminopropyl biguanide (PAPB)/alexidine dihydrochloride (Alexidine)/polyquaternium-1 (PQ-1), Alexidine/PQ-1, and polyhexamethylene biguanide (PHMB)-containing MPSs, as well as the 1 HPS, were significantly superior to myristamidopropyl dimethylamine (MAPD)/PQ-1-based MPSs (all P<.05). Disinfectants PAPB, PHMB, and Alexidine were more effective than MAPD at the studied concentrations for the 3 Gram-negative CL case CIE-associated organisms. A significant aspect of this study is that the disinfection efficacies of 6 MPSs and 1 HPS against 3 CL case CIE-associated organisms were found to be related to the solution and microbe type.
When recommending CL solutions, eyecare practitioners need to consider the efficacy of disinfection against organisms commonly associated with the contamination of CL storage cases. Practitioners should advise patients to adhere to the manufacturer’s guidelines for using CL care solutions, cleaning and disinfecting CL cases, and following recommended replacement schedules for both lenses and cases (Waghmare and Jeria, 2022; Maier et al, 2022A). Additionally, to prevent CIEs and MK, it is pertinent to emphasize the importance of good hand, CL, and CL case hygiene to reduce the risk of CL-associated CIEs and MK (Waghmare and Jeria, 2022; Maier et al, 2022; Corwin-Buell et al, 2025).
References
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2. Maier P, Betancor PK, Thomas Reinhard T. Contact lens–associated keratitis — an often underestimated risk. Dtsch Arztebl Int. 2022;119 (40):669-674. doi:10.3238/arztebl.m2022.0281
3. Ho L, Jalbert I, Watt K, Hui A. Current understanding and therapeutic management of contact lens associated sterile corneal infiltrates and microbial keratitis. Clin Exp Optom. 2021;104(3):323-333. doi:10.1080/08164622.2021.1877530
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5. Steele KR, Szczotka-Flynn L. Epidemiology of contact lens-induced infiltrates: an updated review. Clin Exp Optom. 2017;100(5):473-481. doi:10.1111/cxo.12598
6. Stapleton F, Bakkar M, Carnt N, et al. CLEAR - Contact lens complications. Cont Lens Anterior Eye. 2021;44(2):330-367. doi:10.1016/j.clae.2021.02.010
7. Wu YTY, Willcox M, Zhu H, Stapleton F. Contact lens hygiene compliance and lens case contamination: a review. Cont Lens Anterior Eye. 2015;38(5):307-316. doi:10.1016/j.clae.2015.04.007
8. Corwin-Buell J, Callahan D, McGrath D, et al. Biocidal efficacies of contact lens disinfecting solutions against gram-negative organisms associated with lens case-associated corneal infiltrative events. Clin Ophthalmol. 2025 Feb 14;19:519-526. doi: 10.2147/OPTH.S477777
