Acanthamoeba keratitis is a dreaded corneal infection requiring painful, toxic therapy that can lead to permanent blindness. It’s particularly common among contact lens wearers, occurring most often due to improper storage or failure to remove the lenses prior to showering or swimming. Acanthamoeba adhere to the contact lens first and then to the corneal epithelium and deeper to the stroma. These amoebae are difficult to eradicate and prevention is the best strategy. Recently, a study evaluated silver nanoparticles as possible agents against Acanthamoeba castellanii and found that low concentrations in contact lens solution might help to decrease infection risk.

The researchers examined properties of silver nanoparticles (AgNPs) when conjugated with five multipurpose contact lens solutions against the NEFF strain of Acanthamoeba castellanii in five in vitro assays. Here are some of their findings:

• When Opti-Free (Alcon) was conjugated with AgNP, it behaved in a dose-dependent manner. It reduced Acanthamoeba activity by up to 27.8% after three hours and 23.8% after four hours of incubation, compared to a pure contact lens solution. The researchers noted that they observed increased activity after up to six hours of incubation, which is the minimum time of disinfection for Opti-Free.

• SoloCare Aqua (Menicon) conjugated with AgNPs demonstrated reduced activity up to 17.2% after three hours and 20.3% after four hours of incubation compared to a pure contact lens solution.

• B-Lens, Best View and ReNu MultiPlus (Bausch + Lomb) demonstrated no statistically significant increase in anti-amoebic activity after up to six hours of incubation.

When conjugated with silver nanoparticles, SoloCare Aqua and Opti-Free solutions demonstrated a significant increase in anti-amoebic activity without increasing overall cytotoxicity. The researchers concluded that low concentrations of silver nanoparticles can be used as ingredients in contact lens solutions to help decrease Acanthamoeba keratitis risk. “Strengthening the anti-amoebic properties of contact lens solutions is an urgent need,” the researchers wrote.