Corneal Sensory Nerves and Corneal Epithelial Cells Are in a Codependent Relationship

The intraepithelial corneal nerves are a dense collection of sensory axons that consist of the intraepithelial basal nerves and intraepithelial nerve terminals. The plasma membranes of corneal epithelial cells ensheathe the nerves providing them mechanical support. The nerves, in turn, release trophic factors that nourish the epithelial cells. The corneal nerves grow continuously, and homeostasis is maintained by the diurnally regulated shedding the terminals. In response to injury, severed fragments of sensory axons and terminals along with their mitochondria are internalized by corneal epithelial cells. Some of these axonal mitochondria function metabolically within the corneal epithelium. The health of the corneal epithelium during homeostasis and in response to injury depends on the health of its sensory nerves, and the stability of the sensory nerves depends on the insulation and support provided by the corneal epithelial cells. This mini review describes the unique features of the corneal epithelium and its sensory nerves, highlights their importance, and summarizes how their nomenclature is evolving to reflect recent research findings.