Corneal Nerve Regeneration After Refractive Surgery and the Factors Affecting It—In Vivo Confocal Microscope Study

Abstract PURPOSE To evaluate the regeneration of corneal nerve fibers after small incision microlens extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK) and the factors affecting it. METHODS In this retrospective, nonrandomized observational study, 12 patients underwent SMILE, and 14 patients underwent FS-LASIK for myopia correction. Microscopic morphological changes in subbasal corneal nerve density and corneal structures were assessed by confocal microscopy before surgery and at 1, 3, and 6 months postoperatively. Correlations were made between various subbasal corneal nerve parameters and the corresponding surgical parameters and corneal cell density. RESULTS At one, three, and six months postoperatively, CNFD, CNFL, CNFA, CNFW, and CFracDim were higher in SMILE-treated eyes than in FS-LASIK-treated eyes (all P < .05). However, at 6 months postoperatively, neither group had recovered to preoperative levels. Cap (flap) diameter size was negatively correlated with CNFD at one month postoperatively and with CNFD, CNBD, CNFL, CTBD, CNFA, and CFracDim at three months postoperatively. Preoperative SE was positively correlated with CNFD, CNBD, CNFL, CTBD, and CNFA at three months postoperatively (all P < .01). CONCLUSIONS Up to six months after surgery, the subbasal nerve parameters were higher in the SMILE group than in the FS-LASIK group. Corneal nerve parameters correlated with cap (flap) diameter size as well as SE size at three months postoperatively.