Efficacy of Imidazolium Salt in Disinfecting Soft Contact Lenses Contaminated with Acanthamoeba spp. Trophozoites

Acanthamoeba spp. can infect the cornea due poor lens hygiene allows colonization, and current cleaning solutions are ineffective due to resistant cyst formation. This study aimed to establish, for the first time, a standardized protocol for Acanthamoeba trophozoite adhesion to silicone hydrogel soft contact lenses and to quantify the impact of lens–drug interactions on antiparasitic efficacy. Additionally, the study evaluated the efficacy of 1-hexadecyl-3-methylimidazolium chloride (C16MImCl) against Acanthamoeba trophozoites in the presence of soft contact lenses, in comparison with a commercial contact lens solution and chlorhexidine. A protocol for trophozoites adhesion to silicone hydrogel contact lenses was developed, and the antiparasitic activity of C16MImCl was compared to that of a commercial solution and chlorhexidine. C16MImCl effectively eliminated all trophozoites in the presence of contact lenses and prevented encystment at concentrations ten times the minimum inhibitory concentration, despite partial absorption by contact lenses. Notably, it showed greater corneal cell viability than chlorhexidine, highlighting its potential as a safer alternative. These results underscore its strong anti-amoebic activity, outperforming the commercial solution tested. While further cytotoxicity studies and tests simulating ocular conditions are warranted, C16MImCl emerges as a promising candidate for a future contact lens cleaning and decontamination solution.