Morphology and orientation of corneal nerves after LASEK for the correction of myopia

Abstract

Abstract: : Purpose: Subepithelial nerves and nerves in the anterior stroma of the cornea are damaged during LASEK surgery. The aim of this study was to evaluate the morphology and orientation of recovering stromal nerves and subepithelial nerve fiber bundles (SNFBs) before and after LASEK for the correction of myopia. Methods: In a cross–sectional study corneal innervation was evaluated with a confocal microscope (Nidek ConfoScan 2) in 40 eyes before LASEK and in 20 eyes each 3 month, 6 month and 12 month after LASEK for the correction of myopia (spherical equivalent –2.5 dpt to –10 dpt, mean –4.8 dpt, astigmatism < 1.0 dpt). At every examination the corneas were scanned in full–thickness 3 to 5 times with a z–axis resolution of 5 µm. Parameters assessed at every examination were the number and orientation of stromal nerves per scan and the number and orientation of SNFBs evaluated in the image with the highest density of bundles. Results: Before surgery a mean number of 4.87 SNFBs was found. 91.1% of the SNFBs had a vertical orientation. After 3 month SNFBs were found in 18/20 eyes with a mean number of 2 SNFBs. 84.5% of these SNFBs had a vertical orientation. After 6 month and 12 month a mean number of SNFBs of 3.15 and 3.7 was assessed of which 84.5% and 90.5% respectively had a vertical orientation. The number of stromal nerves was reduced at all timepoints following surgery. Preoperatively the mean number of stromal nerves was 2.25 stromal nerves/scan. After 3, 6 and 12 month 1.88, 1.92 and 1.88 stromal nerves/scan were detected. Stromal nerves mainly had a horizontal orientation before and after LASEK. Conclusions: This study indicates that nerve injury caused by LASEK alters corneal nerve morphology for up to 1 year after LASEK. The orientation of regenerating SNFBs resembled the orientation of SNFBs in the untreated corneas.

Keywords: refractive surgery • innervation: sensation • cornea: clinical science