In vivo observation of corneal nerve regeneration after photorefractive keratectomy with a confocal videomicroscope.

The aim of the present study was to study corneal nerve regeneration after photorefractive keratectomy (PRK) in vivo by means of a confocal videomicroscope. A total of 25 myopic eyes of 16 patients were examined biomicroscopically and with the confocal microscope (Microphthal, Hund Company, Wetzlar, Germany) before and after PRK. The mean age of the patients was 30.4 (range 21-44) years, the mean follow-up period was 13.7 (11.0-15.1) months, the mean preoperative refraction was -5.5 (-1.75 to -9.0) D, the mean amount of attempted correction was -4.75 (-1.75 to -7.5) D, the mean ablation depth was 50 (30-75) microns, and the single central ablation zone measured 6.0 mm in diameter. The postoperative refractive and visual outcome was favorable in most eyes. The mean postoperative refraction was -0.5 (-2.75 to + 0.5) D. Among the 25 eyes, 22 (88%) had +/- 1.0 D of attempted correction at 1 year and only 2 eyes showed a loss of 2 Snellen lines. Despite increased light scattering and reflection due to haze, sufficient postoperative imaging of the corneal nerve architecture was possible in all cases. Recovery of corneal innervation started from the margin of the ablation, being directed toward the center of the cornea and the epithelium. At 5-8 months following PRK, stromal nerves and the subepithelial nerve plexus took on their definite appearance. The original nerve structure was not reestablished, abnormal branching and accessory thin nerve fibers being present without exception. Confocal slit-scanning video-microscopy is a very useful technique for in vivo investigation of corneal nerve regeneration after PRK and, presumably, other keratorefractive procedures. In comparison with histology studies in animals, reinnervation of the human cornea after PRK seems to be completed earlier but follows the same morphologic principles.