title: Corneal reinnervation after LASIK: prospective 3-year longitudinal study.
abstract: OBJECTIVE
  To measure the return of innervation to the cornea during 3 years after LASIK.
  
  
  METHODS
  Seventeen corneas of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D were examined by confocal microscopy before surgery, and at 1, 3, 6, 12, 24, and 36 months after surgery. In all available scans, the number of nerve fiber bundles and their density (visible length of nerve per frame area), orientation (mean angle), and depth in the cornea were measured.
  
  
  RESULTS
  The number and density of subbasal nerves decreased >90% in the first month after LASIK. By 6 months these nerves began to recover, and by 2 years they reached densities not significantly different from those before LASIK. Between 2 and 3 years they decreased again, so that at 3 years the numbers remained <60% of the pre-LASIK numbers (P <0.001). In the stromal flap most nerve fiber bundles were also lost after LASIK, and these began recovering by the third month, but by the third year they did not reach their original numbers (P <0.001). In the stromal bed (posterior to the LASIK flap interface), there were no significant changes in nerve number or density. As the subbasal nerves returned, their mean orientation did not change from the predominantly vertical orientation before LASIK. Nerve orientation in the stromal flap and the stromal bed also did not change.
  
  
  CONCLUSIONS
  Both subbasal and stromal corneal nerves in LASIK flaps recover slowly and do not return to preoperative densities by 3 years after LASIK. The numbers of subbasal nerves appear to decrease between 2 and 3 years after LASIK. The orientation of the regenerated subbasal nerves remains predominantly vertical.
authors.affiliation: Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors.forename: Martha P
authors.initials: MP
authors.lastname: Calvillo
authors.forename: Jay W
authors.initials: JW
authors.lastname: McLaren
authors.forename: David O
authors.initials: DO
authors.lastname: Hodge
authors.forename: William M
authors.initials: WM
authors.lastname: Bourne
mesh_terms: D000328:Adult; D003315:Cornea / Q000294:innervation*; D003319:Corneal Stroma / Q000294:innervation; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008137:Longitudinal Studies; D008297:Male; D018613:Microscopy, Confocal; D009216:Myopia / Q000601:surgery; D009412:Nerve Fibers / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D009882:Ophthalmic Nerve / Q000166:cytology / Q000502:physiology*; D011446:Prospective Studies; D013524:Surgical Flaps / Q000294:innervation