Microbial contamination of contact lenses may lead to corneal infection or inflammatory events such as microbial keratitis (MK), contact lens acute red eye (CLARE) and contact lens peripheral ulcers (CLPUs).
1–4 Pseudomonas aeruginosa is the most common microbe associated with MK during contact lens wear.
5,6 CLARE is commonly caused by Gram-negative colonization of contact lenses,
7–9 and CLPUs are commonly associated with Gram-positive contamination of contact lenses.
9,10 Collectively, along with infiltrative keratitis (IK), which can also be associated with microbial contamination of lenses,
1,7 these adverse events are known as microbially driven corneal infiltrative events (CIEs).
The incidence of MK per year for extended wear of contact lenses is approximately 20 per 10,000 wearers; for daily wear, it is approximately three per 10,000 wearers.
11–15 The incidence of other bacterially driven CIEs is approximately 0.5 to 26.7 per 100 wearers during extended wear
16–19 and 0 to 25.5 per 100 eyes during daily wear.
3,17,20,21 The use of silicone hydrogel lenses has been associated with a two-times greater risk of CIEs.
18
Inhibition of microbial adhesion to contact lenses during wear is likely to reduce the incidence of CIEs. Several potential antimicrobial contact lenses have been produced, although most have not progressed to human clinical trials. Impregnation of silver into etafilcon A hydrogel contact lenses reduced microbial colonization in an in vitro study.
22 Selenium (Se) covalently coated onto balafilcon A silicone hydrogel lenses reduced bacterial colonization in vitro while not adversely affecting the corneal health of rabbits in vivo.
23 The overall clinical performance of the Se-coated lenses was comparable to that of the commercially available balafilcon A lens, and the efficacy of Se-coated lenses was maintained after 24 hours of extended wear.
24 Fimbrolide covalently attached to lotrafilcon A (silicone hydrogel) contact lenses showed good antibacterial activity, and there were no significant differences in ocular responses to fimbrolide-coated lenses compared with uncoated control lenses in either a 1-month animal trial or an overnight human trial.
25 The arginine- and lysine-rich, 29-amino-acid peptide melimine, when immobilized on contact lenses, reduced the severity and incidence of CLARE, CLPUs, and MK in animal models and was not cytotoxic to mammalian cells in vitro.
26–28 Clinical responses to wearing melimine-coated hydrogel contact lenses did not differ from those to wearing uncoated control lenses in animal safety trials; in human trials, an increase in punctate fluorescein corneal staining after 1 day of wear has been reported.
27,28 Due to the increase in punctate fluorescein corneal staining, a shorter derivative of melimine, referred to as Mel4, was developed. Mel4-coated silicone hydrogel lenses (lotrafilcon A, comfilcon A, and somofilcon A) showed a high level of antimicrobial inhibition in vitro and did not have any cytotoxic effects in vivo when rabbits wore them for 1 week.
29 Furthermore, Mel4-coated hydrogel lenses showed no evidence of corneal staining in human phase I clinical trials.
29–31
The current study was designed to determine whether Mel4-coated lenses can reduce the incidence of microbially driven CIEs during extended wear. This study hypothesized that etafilcon A lenses coated with Mel4 would be able to reduce the incidence of microbially driven CIEs due to extended wear.