Many of you rely on your contact lenses in order to help you see, but your lenses could end up taking away your vision. What an ugly irony. The problem starts with a simple single cell microorganism — acanthamoeba.
Acanthamoeba is one of the most common types of protozoan that live in soil and fresh water. They can be found in city tap water, so if you rinse your lens case in water from the sink, this amoeba can be transferred to your contact lenses and then to your eye. These protozoan can live and multiply in both your contact case and your eyes, and can go back and forth between the two because commercial contact lens solution can't kill them. Once they're in your eyes, they can cause a painful infection known as amoebic keratitis, which can lead to blindness. The prevalence of this infection has increased because so many people wear contact lenses now.
The lenses that you wear for a year or two were found to contain the most pathogenic (disease-causing) strains of acanthamoeba. The ones that you keep for a month or two weeks contained fewer, and the daily lenses contained no acanthamoeba. Talk to your eye doctor about the kinds of contact lenses you wear to see which would be the healthiest for your eyes. Scientists are on the move trying to develop a contact lens solution that can kill this nasty amoeba, but for now, it's recommended that you don't rinse your lens case in tap water.