Eye injuries that damage the cornea are usually irreversible and cause blindness. But a new clinical trial has repaired this damage in patients thanks to a transplant of stem cells from their healthy eyes.

The cornea is the outer layer of the eye, which focuses light towards the retina. Since it’s on the frontline of potential hazards from the outside world, the cornea features a population of limbal epithelial stem cells, which repair minor damage to keep the surface smooth and functional.

Unfortunately, injuries like thermal or chemical burns can damage the cornea beyond the capability of these resident stem cells. There’s not much else that can be done – even a cornea transplant won’t take hold if the damage is too severe.