The corneal epithelium represents the uppermost layer of the cornea and consists of abutting tiled cells. It acts as a barrier to protect the cornea from bacteria. The cells that make up the corneal epithelium are grouped in several layers (4-6 layers). Basal epithelial cells, which are found in the bottom layer, have a cylindrical shape and the ability to divide quickly. Emerging cells are then directed to the surface epithelium where they gradually replace dead cells. The epithelium thus has a high capacity for regeneration. The central part contains epithelial cells of square shapes while the outer has flat cells. Dead cells are separated and washed away from the epithelium surface by tears.