Abstract
Purpose :
To evaluate and compare the neuropathic ocular surface changes, corneal nerve imaging and neuromediator profiles in small incision lenticule extraction (SMILE) and femtosecond laser-assisted in-situ keratomileusis (LASIK)
Methods :
In this prospective study, 25 SMILE patients (n=50 eyes) and 25 LASIK (n=50 eyes) were followed up for 1 year. Five clinical neuropathic ocular surface assessments, 7 corneal nerve parameters evaluated by ACCMetrics software, OSDI questionnaire, and the levels of 4 tear neuromediators, were evaluated preoperatively, and 1 week, 1, 3, 6, and 12 months postoperatively.
Results :
SMILE, compared to LASIK, had significantly better corneal sensitivity at 1 week, 1, 3 and 6 months, better tear break-up time (TBUT) at 3 months, lower corneal NEI scores at 1 week, 6 and 12 months, and lower ocular surface Oxford scores 1 week. SMILE had significantly better corneal nerve fiber length (CNFL), density (CNFD), total branch density, fiber area, fiber width (CNFW) and fiber fractal dimension (CFracDim) than LASIK throughout 1year. At 1 year, the nerve metrics were significantly impaired in LASIK, while fiber area and width had been restored in SMILE. There were significant increase in nerve growth factor at 1 month, and decrease in substance P (SP) at 1 month in LASIK, while the changes were insignificant in SMILE. CNFL, CNFD, CNFW, CFracDim and tear SP level were significantly associated with TBUT. Tear SP, neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) concentrations were significantly correlated all the nerve parameters, except CNFW.
Conclusions :
This is the first study comprehensively evaluate and correlate the molecular profiles, morphological changes and clinical functional changes in patients with refractive surgery. The postoperative corneal denervation was long-lasting, with faster restoration in SMILE. SMILE was also associated with less negative impact on ocular surface clinically, as well as less fluctuations in neuroinflammatory reaction. Even though clinical symptoms and signs have subsided, significant alterations in corneal neurobiological status, nerve morphology and quantity were still observed. Our study provides new insights into the biological responses on the ocular surface after refractive surgery.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.