Efficacy and Clinical Performance of Selenium Antibacterial Silicone Hydrogel Contact Lenses

Jerome Ozkan [1] BOptom, Hua Zhu [1],[2] PhD, Mark Willcox [1],[2] PhD.

[1] Institute for Eye Research, Sydney,
[2] School of Optometry and Vision Science, University of New South Wales, Sydney, Australia

Purpose: Bacterial contamination of lenses during continuous wear (CW) is associated with corneal inflammation and infection. Selenium [Se] covalently attached to a surface is a catalytically biocidal agent which can arrest local cellular growth by creating transient, localized, free radicals. Study aims were to evaluate the antibacterial efficacy of Se-coated silicone hydrogel lenses in vitro and ex vivo, and assess cytotoxicity and clinical performance of Se-coated lenses.

Method: Se-coated balafilcon A lenses were challenged with Staphylococcus aureus 31 or Pseudomonas aeruginosa 6294. After 24 hours incubation, bacterial colonization numbers on lens surfaces were enumerated. Biofilm formation on selenium and control lenses were also examined under microscope after stained with florescence by using the LIVE/DEAD BacLight Bacterial Viability Kit. Cytotoxicity of Se lenses was examined by using standard cell growth inhibition assay. To detect difference of 0.5±0.5 in bulbar/limbal redness and 10±15 in comfort rating at 80% power, 20 subjects were required. 20 subjects completed a double masked, contralateral, randomised, controlled clinical trial by wearing Se-coated lens on one eye and standard balafilcon A lens on alternate eye for 24 hours. Clinical assessments were performed during the course of the trial. Lenses were collected aseptically at trial conclusion and assessed for ex vivo antimicrobial activity.

Results: Se-lenses showed significant antimicrobial activity against S. aureus in vitro, reducing colonization of S. aureus 31 by more than 3-log units. Biofilms formed by test strains on Se lenses were markedly less than on control lens surfaces. Se-lenses showed no significant cytotoxicity/cell growth inhibition. Se lenses behaved similarly to control lenses for bulbar and limbal redness. No differences were observed for corneal and conjunctival staining between both lenses. Subjective responses and fitting were also similar. Less conjunctival indentation was observed in the test lens compared to the control lens (0.2±0.6 vs 1.4±1.0, p<0.01). All worn Se lenses showed similar antibacterial activities against S. aureus or P. aeruginosa to unworn lenses.

Conclusion: The results of the study suggest that Se-coated lenses are able to inhibit bacterial colonization. The overall clinical performance of the Se lenses was comparable to the commercially available lens, and the efficacy of Se lenses is maintained after 24 hours CW.