Bacteria live throughout the human body. The eye was long thought to be an exception.

Dr. Anthony St. Leger, a professor of ophthalmology and immunology at the University of Pittsburgh, shattered that notion in 2017 by discovering microbe C. mast lives in the eye — and even helps it stay healthy.

Now, he’s engineering the bacteria to be extra useful alongside several Pitt colleagues.

The group published a study Thursday in the journal Cell Reports that found C. Mast can be genetically modified to secrete an anti-inflammatory protein. The substance helps scratches to the cornea, the outermost layer of the eye, heal 50% faster — at least in mice.

The therapeutic has yet to be tested in people. But if it holds up in human trials, treatment could fundamentally change for a common ailment. More than 1 million people in the U.S. get corneal wounds each year, accounting for about 3% of all emergency room visits, according to statistics cited in the study.

“I have high hopes for it,” St. Leger told TribLive just hours after the paper published.

A shorter healing window reduces the eye’s vulnerability to infection and inflammatory damage, which can have long-term impacts on eyesight. And for people who are already dealing with chronic issues, like dry eye or corneal nerve disorders, C. mast could be engineered in others ways that might be useful.

“We have a platform ready to go and we can just swap out genes of interest,” St. Leger said.

Clinical trials in Europe have shown promise for a similar bacteria-editing technique easing Crohn’s disease symptoms.

The Pitt researchers describe their results as a proof of concept.

Bacteria-based treatments also get around issues with eye drops, which are washed away by tears and require frequent application. Older people report forgetting to use their eye drops 40% of the time, according to one Belgian study.

“You can basically apply it once and let it do its thing indefinitely,” St. Leger said.

The modified bacteria would not be used on humans until scientists identify a way to make it stop producing the anti-inflammatory protein. St. Leger would prefer not to use antibiotics, which disrupt the eye’s microbiome and raise resistance concerns.

“If we’re able to control it… then it’s pretty much like any other drug,” he said.