title: The effect of standard and transepithelial ultraviolet collagen cross-linking on human corneal nerves: an ex vivo study.
abstract: OBJECTIVE
  To evaluate the early effect of standard and transepithelial collagen cross-linking on human corneal nerves in donor eyes by ex vivo confocal microscopy and acetylcholinesterase staining.
  
  
  METHODS
  Experimental laboratory investigation.
  
  
  METHODS
  Eight human eye bank corneal buttons (mean age, 73.6 years) were included. Ultraviolet A collagen cross-linking was performed postmortem on 3 corneas with the standard protocol involving epithelial debridement and 4 corneas by the transepithelial approach. One cornea served as a control. Corneal nerves were evaluated using confocal microscopy and acetylcholinesterase histology.
  
  
  RESULTS
  Confocal microscopy demonstrated the absence of subbasal nerves in corneas treated by the standard technique. These nerves were preserved in corneas treated by the transepithelial approach. Stromal nerves were visible in both groups. Histology of corneas treated by the standard technique revealed localized swellings of the stromal nerves with disruption of axonal membrane and loss of axonal continuity within the treatment zone. These changes were absent in corneas treated by the transepithelial approach.
  
  
  CONCLUSIONS
  This study highlights the immediate effects of collagen cross-linking on the corneal nerves in an ex vivo model. The absence of subbasal nerves in the early phase of treatment appears to be attributable mainly to mechanical removal of epithelium, rather than ultraviolet light-induced damage. Localized swelling of the stromal nerves was the main difference between the 2 treatment protocols. Further research on laboratory animals would be necessary to verify these changes over a specified time course without the super-addition of postmortem changes.
authors.affiliation: Division of Ophthalmology and Visual Sciences, School of Clinical Sciences, University of Nottingham, United Kingdom.
authors.forename: Mouhamed
authors.initials: M
authors.lastname: Al-Aqaba
authors.forename: Roberta
authors.initials: R
authors.lastname: Calienno
authors.forename: Usama
authors.initials: U
authors.lastname: Fares
authors.forename: Ahmad Muneer
authors.initials: AM
authors.lastname: Otri
authors.forename: Leonardo
authors.initials: L
authors.lastname: Mastropasqua
authors.forename: Mario
authors.initials: M
authors.lastname: Nubile
authors.forename: Harminder S
authors.initials: HS
authors.lastname: Dua
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D005125:Eye Banks; D006801:Humans; D018613:Microscopy, Confocal; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000494:pharmacology; D012256:Riboflavin / Q000494:pharmacology; D014019:Tissue Donors; D014276:Trigeminal Nerve / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D000110:Acetylcholinesterase; D012256:Riboflavin