Several critical considerations go into the development of antimicrobial contact lens or storage cases (Willcox et al, 2020; Wu et al, 2015), including their effectiveness against gram-positive and gram-negative bacteria, sustaining that effectiveness after lens-care regimen exposure, biocompatibility with the ocular surface, maintaining stability during contact lens disinfection and storage, and ease of manufacturing (Jones et al, 2021).

Antimicrobial Lenses

Antimicrobial contact lenses incorporated with either silver (Willcox et al, 2010; Nissen and Furkert, 2000) or antimicrobial peptides (Dutta et al, 2014; Dutta et al, 2018) have been extensively studied. Although silver-integrated contact lenses are effective against Pseudomonas aeruginosa, Staphylococcus aureus, and Acanthamoeba castellani (Willcox et al, 2010), they are toxic to ocular surface cells and, at higher concentrations, have affected various properties of lenses, thus limiting their application. While fimbrolide-coated lotrafilcon A contact lenses were able to reduce P. aeruginosa, S. aureus, Serratia marcescens, and Acanthamoeba spp., a higher degree of lens awareness was reported with these lenses (Zhu et al, 2008).

In comparison, antimicrobial peptides—such as melamine, Mel-4, and Esculentin-1a—incorporated into a variety of silicone hydrogel lens materials (including senofilcon A, comfilcon A, somofilcon A, lotrafilcon A, and lotrafilcon B) did not change the lens parameters, yet reduced the adhesion of P. aeruginosa, S. aureus, Fusarium solani, and Acanthamoeba castellani. Additionally, Mel-4-coated lenses were nontoxic and reported to be well tolerated in clinical trials (Dutta et al, 2017).

Antimicrobial Storage Cases

Silver-impregnated contact lens cases were first approved in 2005 (Amos and George, 2006) and were effective when tested in the laboratory (Dantam et al, 2011; Datta et al, 2019). However, clinically, about 70% of storage cases exhibited contamination, regardless of the silver component (Dantam et al, 2012). Studies have shown that incorporating a wipe step in lens case hygiene practice improves removal of bacteria in silver-containing lens cases (Vijay et al, 2020; Wu et al, 2011).

Unlike silver-impregnated cases that can potentially leach, organoselenium-incorporated storage cases showed remarkable activity against a variety of microorganisms (Tran et al, 2017) and did not leach, maintaining a high concentration during their use.

Alternatively, using antifouling coatings on polypropylene cases with surface-modified silica nanoparticles, chemically grafted ultraviolet cross-linkable acrylates and polyethylene glycol (PEG) groups showed an approximate 10-fold reduction in the adhesive forces of nine bacterial strains, including P. aeruginosa, S. aureus, and S. marcescens (Qu et al, 2013; Xiao et al, 2018).

Contamination Sensors

Storage cases with programmed reminders for replacement did not gain users’ attention as anticipated (Hall and Jones, 2010). A patent describing a limited-use, self-destructive contact lens storage case was also never commercialized (Josephson, 2013).

Consequently, research was undertaken on embedding colorimetric biosensors into storage cases that prompt the user to change the contaminated lens case (LeBlanc et al, 2015), which is indicated with a color change from yellow to blue.

Another development (Verma et al, 2014) includes the use of immobilized gold nanoparticles on the surface of the lens case to detect biofilm formation with a color change from blue to purple, prompting disposal of the storage case.

Innovative Packaging

A study confirmed that when compared to conventional blister packages, an innovative 1mm thick flat-pack blister showed decreased contamination, which allows the lens to “spring up” in a hemispherical shape when opened, enabling it to be applied to the eye without touching the inner surface, preventing potential contamination during lens application (Nomachi et al, 2013).

With further advancements in technologies such as those described above, developments in antimicrobial strategies for both contact lenses and storage cases provide promising prospects for safer contact lens wear (Kalaiselvan, Dutta, Konda, et al, 2022; Kalaiselvan, Dutta, Bhombal, et al, 2022; Kalaiselvan et al, 2021). CLS

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