Structural-functional correlations of corneal innervation after LASIK and penetrating keratoplasty.

PURPOSE

To compare corneal subbasal nerve fiber distribution and corneal sensation in healthy humans with findings obtained in regenerated subbasal nerves after LASIK and penetrating keratoplasty (PK).

METHODS

In a comparative case series study, in vivo confocal laser-scanning microscopy was used to investigate subbasal nerve fiber bundles in healthy individuals and at various time points after surgery in patients who had undergone LASIK and corneal grafting. Corneal sensation was measured (Cochet-Bonnet esthesiometer).

RESULTS

In normal corneas investigated, image superimposition revealed the consistent appearance of curved nerve fibers showing a whorl-like pattern with clockwise orientation. Nerve fibers parallel to Bowman's layer originating peripherally traveled radially inwards to a point located at the lower nasal quadrant. This pattern was not seen in any of the patients after LASIK or PK. Regenerated nerve fibers were thinner, more curved, and showed abnormal branching in nearly all patients. Normal corneal neuro-anatomical architecture remained absent even months after total restoration of corneal sensation. After LASIK, normal sensation was regained independently of normal subbasal nerve anatomy. Corneal grafts have shown some recovery of subbasal nerve morphology, at least in the graft periphery, but not complete recovery of function.

CONCLUSIONS

It would appear that normal corneal sensation after LASIK or PK does not always depend on normal subbasal nerve anatomy but on the collateral organization of subbasal nerve fibers.