Long-term Effects of LASIK on Corneal Innervation and Tear Neuropeptides and the Associations With Dry Eye

PURPOSE: To investigate the associations between dry eye, corneal nerves, and tear neuroptides in dry eye after LASIK. METHODS: A single visit cross-sectional study was performed. Twenty participants who had LASIK more than 12 months prior and 20 healthy participants were recruited. Ocular comfort, tear functions, ocular surface sensitivity, basal tear collection, and corneal nerve morphology assessments were conducted. Tear substance P and calcitonin gene-related peptide (CGRP) concentrations were determined using ELISAs. Differences in variables between groups were examined using an independent t test or Mann–Whitney U test, as appropriate. Associations between variables in the post-LASIK group were examined using a Spearman's correlation test. A P value of less than .05 was considered significant. RESULTS: Central corneal nerve morphology parameters were all altered in the post-LASIK group ( P < .05). Higher ocular discomfort ( P = .01), tear CGRP concentration ( P = .001), and conjunctival sensitivity ( P < .009) were found in the post-LASIK group. There was a positive association between dry eye symptoms and superior corneal sensitivity ( P = .51, P = .02) and tear substance P concentration ( P = .52, P < .03). CONCLUSIONS: This study provides evidence of the association between tear neuropeptides, conjunctival sensitivity, and symptoms in symptomatic patients after LASIK. The differences in nerve morphology, neuropeptide, and ocular surface sensitivity between symptomatic and asymptomatic patients after LASIK are required to better understand the mechanism of dry eye after LASIK. [ J Refract Surg . 2016;32(8):518–524.]