Confocal Microscopy in Patients Undergoing Laser In-Situ Keratomileusis (LASIK) after Penetrating Keratoplasty (PK)

Abstract

Abstract: : Purpose: To determine structural and cellular changes of the cornea in patients who underwent LASIK after PK. To also determine visual outcomes of such patients and to assess the effectiveness of LASIK in treating refractive errors after PK. Methods: Prospective and retrospective data were collected from six patients that underwent LASIK after PK. It includes confocal microscopy, visual acuity, manifest refraction, corneal topography, pachymetry, and surgical complications. Results: Pre-LASIK confocal microscopy of the cornea showed the presence of nerves in the subepithelial region and anterior stroma of the cornea. Post-LASIK confocal microscopy at two months after LASIK showed an absence of corneal nerves. Spherical error after PK was reduced by an average of 96.2% after LASIK while cylindrical error was reduced by an average of 52.9% in five patients. In each patient, the cylinder axis indicated by the manifest refraction approximated that indicated by corneal topography. In the sixth patient, the spherical error increased by 4.2% while the cylindrical error increased by 50%. The cylinder axis under manifest refraction did not match that indicated by topography in this last patient. Conclusions: The pre-LASIK confocal microscopy demonstrated corneal nerve regeneration after previous PK. The post-LASIK confocal micrographs demonstrate an absence of these for a post-op interval of at least two months. This is suggestive that a period of at least several months may be required to regenerate corneal nerves in patients undergoing LASIK after PK. These patients will be followed in order to determine the length of time for nerve regeneration to occur. Such a finding is significant in order to properly assess any additional risk involved in performing LASIK on patients that have had previous PK.

Keywords: microscopy: confocal/tunneling • regeneration • refractive surgery: LASIK