Corneal reinnervation following penetrating keratoplasty--correlation of esthesiometry and confocal microscopy

Thus far assessment of corneal reinnervation after penetrating keratoplasty has been possible only by esthesiometry techniques. Since the introduction of confocal microscopy, we have been capable of performing structural corneal in vivo examinations. The purpose of our study was to correlate esthesiometry results with confocal microscopy findings. We used a Cochet-Bonnet esthesiometer and a Microphthal confocal microscope to investigate corneal grafts in vivo. A total of 46 eyes were examined preoperatively and for up to 3 years after penetrating keratoplasty. At 8 weeks after keratoplasty the first stromal nerves were detected in the periphery of the graft. The first nerves in the middle and superficial stroma of the graft center were observed at 7 months after surgery. Reinnervation of the central basal epithelium was found at 2 years after keratoplasty. The highest level of sensitivity was detected in young patients with reinnervation of the basal epithelium. Confocal microscopy enables us to correlate morphologically and functionally corneal reinnervation after surgery. The present study shows that corneal reinnervation is influenced by the amount of time elapsing after surgery, the patient's age, and the preoperative diagnosis. In none of our patients was normal nerve morphology or sensitivity observed during the follow-up period. Comparison of the morphology of nerves seen in eyes after nonsurgical trauma with that observed in corneal grafts indicates that surgically induced scar formation may limit nerve regeneration in grafts.