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Antimicrobial activity declines in tear fluid during contact lens wear
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Postlens tear fluid loses antimicrobial activity when wearing contact lenses, according to a study recently published in Optometry and Vision Science.
Wu and colleagues reported that their results indicate that tear exchange efficiency is vital for homeostasis.
Researchers tested daily disposable lenses in various states as well as tear fluid in order to evaluate antimicrobial activity. Lenses were worn for 1, 2, 4, 6 or 8 hours immediately after opening or after soaking in sterile saline (sodium chloride 0.9%, Winchester Laboratories Germany) for 2 days. Other lenses tested were unworn or were coated in incubated tears for 1 or 8 hours. Researchers utilized Pseudomonas aeruginosa strain PAO1 on the lenses.
Results showed that antimicrobial activity was lower in lenses that had been worn for 8 hours compared to lenses that had been worn for 1 hour if the lenses had been presoaked. This increase was not demonstrated in lenses that were worn immediately out of the package.
"The data presented in this report showed that postlens tear fluid antimicrobial activity could decay over time during contact lens wear," the authors wrote. "Because conjunctival sac-collected tear fluid retained its antimicrobial activity over the same period when incubated in vitro, it is likely that additional in vivo factors are involved in the mechanism for loss of activity under a lens. This phenomenon was less significant for lenses not soaked before placing them in the eye, supporting the possibility that packaging solutions could be used to reduce microbial viability under a lens in vivo."
They concluded: "Contact lens-related infection is a vision-threatening disease impacting otherwise healthy patients. Its incidence has not changed since the introduction of soft contact lenses more than 4 decades ago, despite a plethora of products developed to address it. Contributing to this problem has been a lack of basic research aimed at understanding pathogenesis.”
The researchers said these study results indicate changes to the postlens tear film that favor microbial survival and suggest strategies to address the problem. They noted that a larger clinical study is warranted due to the limitations of this study to determine how widely applicable these findings would be. – by Chelsea Frajerman Pardes
Disclosures: Fleiszig is a paid consultant for Allergan Inc.
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