Degeneration and regeneration of corneal nerves.

CERTAIN authors, such as Haab (1899), Kraupa (1924), and Walsh (1947), have suggested that there might be an inter-relation between certain diseases of the cornea and the condition of the corneal nerves. The diseases mentioned are recurrent erosion of the cornea, superficial punctate keratitis, herpetic keratitis, and certain forms of degeneration of the corneal epithelium. Neuroparalytic keratitis and herpes zoster ophthalmicus are known to be dependent on injury to or disease of the ophthalmic division of the trigeminal nerve. Before attempting to study diseased conditions of the corneal nerves, an exact knowledge of the normal corneal innervation and of the reactions of the nerves to simple traumatic injury is necessary. Results obtained from experimental work on animals should to a certain extent be applicable to processes in the human corneal nerves. Such investigations have been made by Leoz Ortin (1915), who studied the corneal sensitivity after partial and total keratotomy. He obtained a corneal reflex 60 days after the operation, and found good nerve regeneration in histologic sections taken 8 months after the operation. Jent (1945) performed circular incisions of the corneal stroma down to Descemet's membrane and then examined the nerves in vital staining. He also studied the corneal sensitivity in these cases with von Frey hairs. He found that the nerves were less stainable after 24 48 hours, after 5 days they could not be stained at all ; after 28 days, small sprouting neurites could be stained in the old pathways.