Tear dynamics and corneal sub-basal nerve fiber regeneration after laser in situ keratomileusis flap made with microkeratome or Femto LDV femotosecond laser
Objective To investigate changes in tear dynamics and corneal sub-basal nerve fiber regeneration after laser in situ keratomileusis (LASIK) surgery with a femtosecond laser and a mechanical microkeratome. Methods In a prospective case-control study, 40 eyes of 20 patients were treated with FEMTO LDV femtosecond laser LASIK surgery (F-LASIK group) or mechanical microkeratome LASIK surgery (M-LASIK group) respectively. Tear film break-up time (BUT), Schirmer I test with corneal fluorescein staining (FS) and in vivo confocal microscopy of corneal subbasal nerve fibers (CSNFs) were obtained preoperatively and 1 and 3 months after surgery. Images of the CSNFs were analyzed to evaluate nerve regeneration. Data were analyzed using repeated measures ANOVA, an independent samples t test, Mann-Whitney U test and Spearman correlation analysis. Results At 1 and 3 months after operation the average of BUT of F-LASIK group was significantly longer than that of M-LASIK group (t=-2.195, -2.174, P<0.05). Schirmer I test results and the FS were comparable between the 2 groups. The nerve regeneration score was a little higher in F-LASIK group (1.03±0.63) than that in M-LASIK group (0.83±0.55) at 1 month after surgery, but there was no significant difference (Z=-1.400, P>0.05). The nerve regeneration score in F-LASIK group (2.31±0.83) was significantly higher than that in M-LASIK group (1.93±0.80) at 3 months after surgery (Z=-2.100, P<0.05). Significant positive correlations were found between Schirmer I test and the CSNFs regeneration score (r=0.231, P<0.01), while there was no statistically significant associations between the CSNFs regeneration score and BUT (r=0.143, P>0.05) or FS (r=-0.049, P>0.05). Conclusion The recovery of tear dynamics and corneal subbasal nerve fibers is faster in FEMTO LDV LASIK than in traditional LASIK. Schirmer I test is increase with the CSNFs regeneration.
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