Prolonged Retrobulbar Local Anesthesia of the Cornea Does Not Cause Keratopathy in Mice

• Main Authors: Innocent, C. (Author), Kohane, D.S (Author), Liu, A. (Author), Mehta, M. (Author), Zhao, C. (Author)
• Format: Article
• Language: English
• Published: Association for Research in Vision and Ophthalmology Inc. 2022
• Subjects: adverse event; Anesthesia, Local; Anesthetics, Local; animal; animal experiment; animal model; animal tissue; Animals; Article; confocal microscopy; controlled study; cornea; Cornea; cornea injury; Corneal Dystrophies, Hereditary; enzyme linked immunosorbent assay; female; Female; fluorescein; fluorescein sodium; follow up; hereditary corneal dystrophy; histology; histopathology; immunohistochemistry; keratitis; Keratitis; keratopathy; Keratopathy; local anesthesia; local anesthetic agent; Mice; mouse; neurokinin A; Neurotrophic; neurotrophic keratopathy; neurotrophin; nonhuman; optical coherence tomography; plasma exchange; polymerization; retina hemorrhage; retrobulbar anesthesia; Retrobulbar anesthesia; slit lamp microscopy; tetrodotoxin; transmission electron microscopy; vasculotropin; visual analog scale
• Online Access: View Fulltext in Publisher

 Purpose: Prolonged local anesthesia (PLA) of the cornea is currently assumed to cause neurotrophic keratitis and is strongly discouraged. We investigate whether PLA of the cornea per se causes neurotrophic keratitis. Methods: PLA of the cornea was induced in 12 female albino BALB/c mice by retrobulbar injection of a polymeric prodrug (PGS-TTX) where the site 1 sodium channel blocker tetrodotoxin (TTX) was slowly released from the polymer polyglycerol sebacate. The duration and depth of corneal anesthesia was monitored by the Cochet-Bonnet esthesiometer. Corneal injury from PLA was assessed by slit lamp examination with 2% sodium fluorescein dye, histology, corneal nerve density by immunohistochemistry with anti-β III tubulin antibody and confocal microscopy, and corneal neurotrophin levels (substance P and neurokinin A) by an enzyme-linked immunosorbent assay. PLA was also induced by topical amitriptyline (80 mM), used as a positive control for local anesthetic-induced corneal injury. Frequent ocular lubrication was provided. Results: Retrobulbar PGS-TTX resulted in complete corneal anesthesia lasting 50.1 ± 3.6 hours and mean time to complete resolution of block of 55.1 ± 3.6 hours with no keratopathy provided lubrication was provided. Topical 80 mM amitriptyline induced complete corneal anesthesia for 24 hours and developed keratopathy. There was no difference in the histology, levels of corneal neurotrophins, and corneal nerve density between the retrobulbar PGS-TTX group and normal cornea. Conclusions: In the absence of topical toxicity or corneal exposure, PLA of the cornea per se does not cause keratitis. Translational Relevance: PLA of the cornea could be highly beneficial in acute and chronic painful corneal conditions. © 2022 The Authors.