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 a fter photorefractive keratectomy (PRK) in vivo by means of a confocal videomicroscope. A total of 25 myopic eyes of 16 patients were examine d biomicroscopically and with the confocal microscope (Microphthal, Hu nd Company, Wetzlar, Germany) before and after PRK. The mean age of th e 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) mu m, and the s ingle central ablation zone measured 6.0 mm in diameter. The postopera tive refractive and visual outcome wag favorable in most eyes The mean postoperative refraction was -0.5 (-2.75 to +0.5) D. Among the 25 eye s, 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 scatte ring and reflection due to haze, sufficient postoperative imaging of t he corneal nerve architecture was possible in all cases. Recovery of c orneal innervation started from the margin of the ablation, being dire cted 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 re established, abnormal branching and accessory thin nerve fibers being present without exception. Confocal slit-scanning videomicroscopy is a very useful technique for in vivo investigation of corneal nerve rege neration 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.