Comparative antimicrobial efficacy of soft and rigid gas permeable contact lens solutions against Acanthamoeba.

Ten soft contact lens cleaners, three rigid gas permeable contact lens (RGP) disinfecting-soaking solutions, and four hydrophilic contact lens disinfecting solutions were evaluated by laboratory challenge procedures for their antimicrobial efficacy against trophozoites and cysts of Acanthamoeba polyphaga and Acanthamoeba castellanii. MiraFlow was the only cleaner that killed trophozoites and cysts on all lenses during the cleaning step. A disinfecting solution preserved with chlorhexidine and one preserved with benzalkonium chloride killed trophozoites of A. polyphaga within 4 hours, but cysts persisted in both solutions for at least 2 days. Cysts of A. polyphaga survived in three disinfecting solutions up to one week, whereas those of A. castellanii were recovered from six disinfecting solutions at 7 days. An RGP solution that is marketed only in Japan was effective against trophozoites and cysts of both species within 30 minutes.