Over 30 million Americans enjoy the technological delight of contact lenses — a number so high that it’s easy to forget how super gross contacts can actually be. Much of that is because of human error: The Centers for Disease Control report that between 40 to 90 percent of contact lens-wearers don’t properly follow the care instructions, meaning they are much more susceptible to developing inflammation infections infections like conjunctivitis and keratitis.

A study published today in the journal mBio could have implications for discovering why these disease risk factors exist. Researchers from New York University’s School of Medicine found that wearing contact lenses actually changes the microbial structure of the eye’s conjunctiva, causing it to become more similar to that of skin microbiota.

In other words, wearing contacts makes your eyes more like your skin.

Like the mouth or gut, an eye has its own community of bacteria that protects it from pathogens. This is the ocular microbiota, which has largely been neglected in scientific study but we know is important for keeping the eye healthy. The main reason why having skin microbiota in the eye is a concern is that researchers hypothesize this may be the reason why contact lens wearers are more at risk for eye infections. The community of symbiotic and pathogenic microorganisms that live in your eye goo can’t do their job right.

A contact lens-free eyeball.

Researchers analyzed 20 subjects, divided into lens wearers and non-lens wearers. For each person, the researchers used a gene-based sequencing technique to take three samples of bacterial communities of conjunctiva, and the skin that is under the eye. Compared to non-lens wearers, they found that lens-wearers had more skin-linked bacterial structures in their eyes.

The researchers need to conduct more studies before they can definitively link their findings with the protraction of eye disease, but they do believe the results suggest that skin bacteria decreases the “self-restoring capacity of the ecosystem” of the eye.

How this bacteria gets in the eye isn’t clear, though — study author Maria Dominguez-Bello told Phys.org that it could be that “these bacteria are transferred from fingers to the lens to the eye of the surface, or if the lenses exert selective pressures on the eye bacterial community in favor of skin bacteria.” However, in this study when the team tested whether the bacteria originated from the hands of the subjects, the results suggested that nope, it did not.

In the meantime, people who wear contacts should follow the advice of the CDC and actually take their lenses out and clean them properly. If that doesn’t convince you maybe, this stat will: One million Americans develop keratitis — an inflammation of the corneas — a year, a disease that is 20 times more likely to develop if someone sleeps with their contacts in.


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