Scientists have learned plenty about the colonies of bacteria living in our gut: how they protect against pathogens, and how we can change them, for better and for worse, by what we put into our bodies.

A similar thing seems to happen at another unexpectedly bug-filled body site: the eyeball. Popping in contact lenses changes the eye’s bacteria by making it more skin-like, according to a new study published in the journal mBio.

In the study, which built upon the early results of research last year, researchers from the New York University School of Medicine wanted to see what was living on the ocular microbiota of 58 people—some who wore contacts lenses and some who did not. The team swabbed the surfaces of the eyeball, as well as the skin under the eye, and sequenced the bacterial communities.

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The researchers found that contact lenses changed the bacterial composition of the eye surface to make it more similar to skin: meaning lens-wearers had a greater abundance of skin bacteria including Pseudomonas, Acinetobacter, Methylobacterium and Lactobacillus and lower abundances of Haemophilus, Streptococcus, Staphylococcus and Corynebacterium than people who didn’t wear contacts.

“Wearing contact lenses is known to increase the risk of microbial keratitis and other inflammatory eye conditions,” says senior study author Maria Dominguez-Bello, an associate professor of medicine at New York University, in an email. Still, it’s too soon to say whether these microbial changes are responsible for compromised eye health. “Future studies are needed to determine the role of the microbiome in the increased risk for eye infections in contact lens wearers,” she says.

Write to Mandy Oaklander at mandy.oaklander@time.com.