Neurotrophic keratopathy is a degenerative disease characterized by decreased corneal sensitivity and poor corneal healing. This disease leaves the cornea susceptible to injury and decreases reflex tearing. Epithelial breakdown can lead to ulceration, infection, melting, and perforation secondary to poor healing. The common factor in all cases of neurotrophic keratopathy is corneal hypesthesia.
Sensory nerves exert a trophic influence on the corneal epithelium.
The sensory neuromediators, acetylcholine, substance P, and calcitonin gene-related peptide, have been shown to increase epithelial cell proliferation in vitro. Denervation results in decreased cell metabolism, increased permeability, decreased levels of acetylcholine, and decreased cell mitosis. Because a continuous turnover of corneal epithelial cells occurs, this can lead to an epithelial defect even in the absence of injury. Sympathetic neuromediators and prostaglandins decrease epithelial cell mitosis. In fact, ipsilateral sympathetic denervation appears to mitigate the effects of corneal sensory denervation.