Corneal endothelial cells do not naturally regenerate; when lost, they are gone forever.
As endothelial cell loss worsens:
The remaining cells can spread to cover the exposed portions of the cornea to maintain visual function
However, as corneal endothelial cells enlarge and as density decreases to 400 cells/mm2 or fewer, the remaining cells may be unable to keep the cornea dry and maintain functional vision
Corneal edema (swelling) may occur, with associated vision loss
In addition, epithelial edema may occur, which can result in a painful, debilitating foreign body sensation in the eye