Sight-robbing injuries to the cornea can be repaired using a groundbreaking experimental stem cell treatment, a new study shows.

The cornea — the clear outermost layer of the eye — can become irreversibly damaged if injury or disease destroys its ability to regenerate new cells.

In this new process, stem cells taken from a person’s healthy eye can be used to rebuild the cornea in their damaged eye, researchers reported March 4 in the journal Nature Communications.

The process has proven feasible and safe in 14 patients who were treated and followed for 18 months, early clinical trial results show.

The treatment is called cultivated autologous limbal epithelial cells, or CALEC.

“Our first trial in four patients showed that CALEC was safe and the treatment was possible,” lead investigator Dr. Ula Jurkunas, associate director of the Cornea Service at Mass Eye and Ear in Boston, said in a news release.

“Now we have this new data supporting that CALEC is more than 90% effective at restoring the cornea’s surface, which makes a meaningful difference in individuals with cornea damage that was considered untreatable,” she said.

The outer border of the cornea, the limbus, contains many healthy stem cells called limbal epithelial cells, researchers explained in background notes. These cells constantly rebuild the cornea, keeping it clear and smooth.

When a person’s cornea is damaged, the injury can deplete the limbal epithelial cells. As a result, the surface of the eye develops permanent damage — a condition called limbal stem cell deficiency.

Worse, this damage can render the eye unfit for cornea replacement surgery, which replaces a damaged or diseased cornea with donor tissue, researchers said.

CALEC involves removing stem cells from a healthy eye and then expanding them into a tissue graft using a new manufacturing process that takes two to three weeks, researchers explained.

The graft is then surgically transplanted into the eye with a damaged cornea, restoring the cornea’s ability to regenerate.

CALEC completely restored the cornea in half of study participants within three months, and that rate of success increased to around 80% after a year and a half, results show.

The overall success rate of CALEC came in around 90% when considering those who achieved partial recovery, researchers said.

The procedure also proved safe, with no serious adverse events occurring in either the donor or the damaged eye of the patients, researchers said.

The procedure is still experimental, and further clinical trials will be needed before CALEC is submitted for federal approval, researchers said.

“We feel this research warrants additional trials that can help lead towards [U.S. Food and Drug Administration] approval,” Jurkunas said.

In the meantime, researchers hope to refine the procedure.

For example, now a person must still have one healthy eye to serve as a stem cell donor to the damaged eye.

Researchers eventually want to be able to perform the procedure using stem cells taken from the eyes of deceased donors.

“This will hopefully expand the use of this approach and make it possible to treat patients who have damage to both eyes,” researcher Dr. Jerome Ritz, executive director of the Dana-Farber Cancer Institute’s Cell Manipulation Core Facility, said in a news release.

More information

The American Academy of Ophthalmology has more on limbal stem cell deficiency.

SOURCE: Mass General Brigham, news release, March 4, 2025

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