At any given time, more than 30 million Americans are sporting prescription contact lenses. Wearers are typically given rigid instructions for keeping them sterile and preventing contamination during insertion or removal, but new research suggests users may be harboring more bacteria in the eye than previously believed.

The Human Microbiome Program at New York University School of Medicine recently published a study involving 58 adults in the journal mBio that found an increased level of bacteria on the eye surface of contact-lens wearers compared to subjects who do not wear contacts. The bacterial profile was found to be similar to the surface of the skin surrounding the eye: skin bacteria such as Pseudomonas, Lactobacillus, and Acinetobacter were among the bacteria strains found, none of which are typically seen in high concentrations on the ocular surface. Meanwhile, the eyes of contact-lens wearers were lower in bacteria such as Haemophilus and Streptococcus than those of non-lens wearers. 

The study authors say it’s too premature to implicate the lenses directly: It’s possible an insufficient hygiene regimen is at fault. The Centers for Disease Control estimates anywhere from 40 to 90 percent of users don’t follow proper protocol for handling. To minimize the chances for infection, the CDC says it’s important to wash your hands before touching the lenses and to keep them cleaned after wearing and before storage with a sanitizing solution (not water). You should also pay attention to the lens case, wiping it down with solution and replacing it every three months. Failure to do so has been linked to serious eye infections. 

Additionally, you never want to shower, jump into a hot tub, swim, or sleep in them. Irritation, pain, or redness should be reported to your eye doctor.

[h/t ScienceDaily