A degenerative eye condition where damaged corneal nerves can’t maintain the cornea’s surface—leading to persistent ulcers that won’t heal.Neurotrophic keratitis (NK) is a degenerative corneal disease caused by impaired trigeminal innervation, resulting in reduced corneal sensitivity, epithelial breakdown, and impaired healing. Classified in three stages: Stage 1 (punctate keratopathy), Stage 2 (persistent epithelial defect), Stage 3 (corneal ulcer with stromal melting). Cenegermin (recombinant human NGF) is the first FDA-approved treatment, directly addressing the neurotrophic deficit. RGN-259 (thymosin beta-4) and other peptide-based eye drops are in development for corneal nerve regeneration.