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The magic clear disks that bring your world into focus may be doing some bad things to your eye bacteria, a new study suggests.

“The eye has a normal community of bacteria, expected to confer resistance to invaders,” says senior study investigator Maria Gloria Dominguez-Bello, PhD, associate professor of the Human Microbiome Program at New York University School of Medicine. But inserting contact lenses seems to mess with that delicate balance, the researchers found.

They wanted to compare the colonies of bacteria living on the eyeballs of people who wear contact lenses to the eyes of those who don’t, so they recruited 20 people in the new research, presented at the annual meeting of the American Society for Microbiology. They swabbed different parts of the eye, sequenced the bacteria and found major differences between lens-wearers and people who didn’t wear lenses. Bacteria inside the eyes of contacts-wearers looked more like the colonies of bacteria found on their skin than those normally found in eyes, compared to the normal bacteria of the lens-free group.

That might be because finger skin bacteria lingers on the lenses, which is then transferred to the eye’s surface, suggests Dominguez-Bello. Another possible explanation: the lenses may favor skin-like bacteria over the kind normally found in the eye.

Either way, it doesn’t look good for lens-wearers, who had enriched communities of pathogens that play key roles in conjunctivitis, keratitis and endophthalmitis—all inflammatory eye conditions, says Dominguez-Bello. Using contact lenses has been linked to eye diseases and infections and is considered a risk factor for keratitis.

The study is too small and preliminary to warrant eye-care changes, but Dominguez-Bello calls for more research on the eye microbiome, a bacteria-rich community overlooked in the growing microbiome research focused on the gut and skin. “Despite being important in ophthalmology, the eye microbiome has been largely neglected, and its functions remain unknown,” she says.

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Write to Mandy Oaklander at

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