Contact lenses offer an excellent alternative to spectacles to correct refractive errors. Indeed, they are superior to spectacles in many ways offering better peripheral vision and also the possibility of preventing the progression of refractive errors such as myopia. However, wearing contact lenses can cause ocular inflammation and infection. If not treated quickly and with appropriate antibiotics, the infections can progress rapidly and lead to loss of vision, even the whole eye. Contact lens-induced inflammation and infection are most commonly caused by bacteria, initially adhering to contact lens surfaces. Thus, creating antimicrobial contact lenses has the potential to reduce these adverse responses and make contact lens wear safer.
We have produced contact lens coated with a cationic antimicrobial peptide, melimine. Melimine is a membrane active antimicrobial that causes cell lysis. Importantly, growth of bacteria in sub-inhibitory concentrations does not result in bacteria becoming resistant. Laboratory experiments have shown that these lenses are active against Pseudomonas aeruginosa(incl. multi-drug resistant strains), Staphylococcus aureus(incl. MRSA), Serratia marcescens, Candida albicans, and Acanthamoebasp.
After safety testing using standard in vitro and in vivo (animal) tests, the lenses were tested in 1-day trials using human subjects. There were no adverse clinical responses other than slight increase in corneal staining. Due to this, we redesigned the peptide to produce a shorter version, Mel4, that was also safe to wear, and produced no staining when attached to contact lenses. Mel4-coated lenses have finished large scale Phase II/III clinical trials with subjects wearing lenses for 3 months on a 14-day lens replacement schedule. These lenses reduced the incidence of ocular inflammation by 50%.