Journal of Cellular and Molecular Medicine · 6 authors, 8 centres
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This prospective study compared changes in tear film antioxidants after two common refractive surgeries. Ascorbic acid (AA) decreased significantly after both procedures, but the reduction was significantly greater after femtosecond LASIK (FS-LASIK) than after laser-assisted lenticule extraction (LALEX). The findings suggest LALEX may be preferable for patients with dry eye disease or high myopia due to better preservation of antioxidant levels.
**Background:** Oxidative stress plays a role in ocular surface diseases including dry eye disease (DED). Refractive surgeries like femtosecond laser in situ keratomileusis (FS-LASIK) and laser-assisted lenticule extraction (LALEX) induce inflammation and may alter antioxidant levels in the tear film. This study aimed to compare changes in total antioxidant capacity (TAC) and ascorbic acid (AA) between these two procedures.
**Methods:** A prospective non-randomized study was conducted at Nobel Eye Clinic, Taipei. Inclusion criteria: age 20-50 years, myopia ≥ -1.00 D, ability to understand study details. Exclusion criteria included severe ocular pathology, unstable refraction, pregnancy, and active inflammatory diseases. After selection, 75 eyes (38 participants) underwent LALEX and 33 eyes (17 participants) underwent FS-LASIK. Tear film samples were collected near the corneal incision using Schirmer strips pre-operatively, 1 week, and 1 month post-operatively. TAC and AA concentrations were measured using a colorimetric assay (Oxiselect Ascorbic Acid Assay Kit). Statistical analysis included independent t-tests, paired t-tests, and generalized linear mixed models adjusting for age, sex, sphere power, cylinder power, intraocular pressure, Schirmer test results, central corneal thickness, optic zone, and baseline antioxidant levels.
**Key Results:** Baseline characteristics were similar between groups except FS-LASIK had higher sphere power (-7.56 ± 2.79 vs -5.79 ± 2.02 D, p=0.0001) and smaller optic zone (6.37 ± 0.28 vs 6.54 ± 0.23 mm, p=0.0001). Pre-operative TAC was higher in LALEX (669.11 ± 261.74 vs 575.41 ± 387.70 mM, p=0.0124). AA decreased significantly 1 month post-operatively in both groups (LALEX: 374.36 ± 117.40 vs 428.16 ± 199.04, p=0.0028; FS-LASIK: 278.25 ± 178.96 vs 363.29 ± 113.99, p=0.0001). The decrement in AA was significantly larger in FS-LASIK (adjusted odds ratio [aOR] 0.799, 95% CI 0.665-0.854, p=0.0056). TAC changes were not significantly different between groups (aOR 0.996, 95% CI 0.201-1.857, p=0.6012). In subgroup analyses, LALEX showed lower TAC decrement in DED patients (aOR 0.889, 95% CI 0.707-0.961, p=0.0449) and lower AA decrement in high myopia (aOR 0.840, 95% CI 0.623-0.962, p=0.0377) and DED (aOR 0.763, 95% CI 0.694-0.817, p=0.0035).
**Clinical Implications:** LALEX surgery results in less AA depletion compared to FS-LASIK, particularly in patients with DED and high myopia. This may be due to lower laser energy and reduced thermal effect in LALEX. The findings suggest LALEX may be a better option for patients at risk of oxidative stress-related complications. Clinicians should consider more frequent artificial tear use or antioxidant supplementation for patients undergoing FS-LASIK, especially those with DED or high myopia. Limitations include small sample size, short follow-up (1 month), and inability to measure intrastromal antioxidant levels directly.