Contact Lens Solutions Ineffective Against Acanthamoeba, Study Finds

February 20, 2012

Leading brands of contact lens solutions are ineffective at killing Acanthamoeba microorganisms that can cause serious eye infections and vision loss, according to a new study.

Acanthamoeba is a type of amoeba (ah-MEE-bah), which is a single-cell microorganism with an indistinct shape that is commonly found in soil, fresh water and tap water. It also survives in chlorinated swimming pools and hot tubs. Infection of the front surface of the eye by Acanthamoeba is called Acanthamoeba keratitis.

Researchers in Hong Kong evaluated four leading brands of multipurpose solutions and a hydrogen peroxide disinfecting system (Oxysept) for soft contact lenses (including silicone hydrogel contacts) and four brands of multipurpose solution for rigid gas permeable contact lenses for their effectiveness at killing three species of Acanthamoeba.

The study also evaluated whether the presence of protein deposits on the lenses influenced the disinfecting effectiveness of the solutions.

Results of the study revealed that none of the contact lens solutions achieved a significant reduction of the viability of all three types of Acanthamoeba when used for the manufacturers’ recommended disinfection times. The presence of protein on the lenses further reduced the effectiveness of all the contact lens solutions tested.

A full report of the study appears in the January 2012 issue of Optometry & Vision Science.

Chief Clinical Editor’s comment:

This study underscores the importance of not wearing contact lenses while swimming and avoiding the use of tap water to rinse your lenses or lens case — activities that increase your risk of exposing your eyes to Acanthamoeba microorganisms. It also supports the rationale of using a “rub-and-rinse’ method of lens care, since this method can help keep Acanthamoeba from adhering to the surface of contact lenses. Finally, replace your contact lenses and lens case frequently to avoid protein deposits that appear to further decrease the disinfecting effectiveness of contact lens solutions. – Gary Heiting, OD