Early Experiences with Antibacterial Silicone Hydrogel Contact Lenses

Jerome Ozkan is a Research Optometrist at the Institute for Eye Research in
Sydney, Australia. He is a Principal Investigator in human clinical trials
being conducted to test the safety and efficacy of new contact lens
materials and designs. Most recently, Jerome has been involved in human
trials testing hypotheses to determine the aetiology of adverse events
during daily wear and extended wear of contact lenses.

The Institute for Eye Research has conducted several short term clinical trials testing the safety and efficacy of investigational antibacterial contact lenses. By developing an antibacterial contact lens that prevents bacterial adhesion we are hoping to reduce the occurrence and severity of infection and inflammation caused by various microbes. Two antibacterial compounds that have been assessed, in separate human clinical trials, are fimbrolides and selenium.

Bacterial compounds called quorum-sensing molecules allow bacteria to communicate with each other and form impenetrable biofilm surfaces that make bacteria resistant to antibiotics. Fimbrolides (also known as furanones) are quorum-sensing inhibitors that disrupt this bacterial communication. Selenium is required by our bodies for normal metabolic function but it has other properties that include an ability to produce oxygen radicals. These are a very reactive oxygen species and can kill bacteria.

A recently conducted clinical trial assessing selenium lenses was powered to detect a difference in bulbar/limbal redness and subjective comfort responses. A total of 20 subjects completed a double masked, contralateral, randomised, controlled clinical trial by wearing selenium-coated lens on one eye and standard balafilcon A lens on the 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. The results of the controlled clinical trial showed that selenium coated 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 selenium-coated test lens compared to the commercial control lens. All worn selenium-coated lenses showed similar antibacterial activities against S. aureus or P. aeruginosa to unworn lenses. Results have been promising, demonstrating that selenium-coated lenses can prevent colonisation of the surface by bacteria and that overall clinical performance of the lenses was comparable to the commercially available lens. A similarly designed trial was also conducted to assess furanone coated lenses. The overall clinical performance of the antibacterial furanone-coated lenses in the overnight extended wear trial was comparable to the commercially available lenses. Ex vivo analysis of the lenses confirmed that the coated lenses prevented adhesion of a range of microbes.   

The Institute for Eye Research is now scaling up various forms of the antimicrobial lenses for further clinical evaluation.