title: An evaluation of corneal nerve morphology and function in moderate keratoconus.
abstract: OBJECTIVE
  To investigate corneal nerve morphology and corneal sensitivity in keratoconus.
  
  
  METHODS
  The central cornea of 13 subjects with keratoconus and 13 age-matched control subjects was assessed using in vivo confocal microscopy and corneal aesthesiometry.
  
  
  RESULTS
  Significant differences in corneal nerve fibre density were found between the subjects with keratoconus and the control subjects (keratoconus versus control; 1018.3+/-489.6 microm versus 1820.7+/-789.5 microm; p = 0.006). The mean diameter of nerve fibres in the stroma was found to be greater in subjects with keratoconus compared to control subjects (keratoconus versus control; 10.2+/-4.6 microm versus 5.5+/-1.9 microm; p = 0.007). The orientation of corneal nerve fibres in the subjects with keratoconus appeared to be altered from the predominantly vertical orientation seen in the control subjects. Corneal touch threshold was found to be similar in the two groups, although the subjects with keratoconus using contact lens correction had reduced corneal sensitivity compared to the contact lens-wearing control subjects (keratoconus with contact lenses versus controls with contact lenses; 1.18+/-0.19 g/mm2 versus 0.98+/-0.05 g/mm2; p = 0.03).
  
  
  CONCLUSIONS
  This study reveals significant reductions in nerve density in the keratoconic cornea. The thickened stromal nerve fibres observed in the keratoconic corneas may explain why prominent corneal nerves are often seen using slit lamp biomicroscopy in keratoconic patients.
authors.affiliation: Optometry and Neuroscience, Moffat Building, The University of Manchester, PO Box 88, Manchester, M60 1QD, UK. Maria.L.Simo-mannion@manchester.ac.uk
authors.forename: Luisa
authors.initials: L
authors.lastname: Simo Mannion
authors.forename: Cindy
authors.initials: C
authors.lastname: Tromans
authors.forename: Clare
authors.initials: C
authors.lastname: O'Donnell
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology; D003315:Cornea / Q000294:innervation* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D009412:Nerve Fibers / Q000648:ultrastructure*; D009882:Ophthalmic Nerve / Q000473:pathology*; D011446:Prospective Studies; D012684:Sensory Thresholds; D012720:Severity of Illness Index