Acanthamoeba is a leading cause of eye infection on contact lens wearers, particularly in people that use soft lenses. It can cause keratis of the eye and may eventually lead to blindness. In the British Journal of Ophthalmology, K. Hiti and colleagues, from the University of Vienna, Austria, tested the ability of three types of cleaning solutions for soft contact lenses to kill the single-cell organism Acanthamoeba (Br J Ophthalmol 2002, 86:144-146).

The organism has two distinct life stages: trophozoites and the less active cysts. While all three solutions had killed the trophozoites of all the strains of Acanthamoeba, they were not able to kill all the cysts.

Hiti et al. tested a multipurpose storage solution, a one-step 3% and a two-step 0.6% hydrogen peroxide solution. All three solutions were tested for 30 minutes and then eight hours. The two-step 0.6% hydrogen peroxide solution was the most effective, killing almost all the cysts, with some eradicated after just 30 minutes. The multipurpose solution was less effective, but was able to kill cysts from at least some of the Acanthamoeba strains. But, they found that cysts from all strains were still alive with the one-step 3% hydrogen peroxide solution, even after eight hours.

They noted that, as hydrogen peroxide is toxic to the eye, it must be neutralized. The one-step solutions use a catalyst to do this, which the team suggested acts too quickly to give enough time to kill the Acanthamoeba cysts effectively. They concluded: "The development and use of storage solutions which are effective against Acanthamoeba is of great importance."