[Corneal subbasal nerve density changes after laser in situ keratomileusis with mechanical microkeratome and femtosecond laser]

Abstract

Objective: To compare the corneal subbasal nerve density (SND) changes after laser in situ keratomileusis (LASIK) with a microkeratome and a femtosecond laser.

Methods: Prospective clinical study. Sixty eyes of thirty myopes were included. Fifteen patients (30 eyes) underwent LASIK with the Moria II microkeratome, and the other 15 patients (30 eyes) with the 60 k Hz IntraLase femtosecond laser. Central, temporal and nasal corneal SNDs were measured by confocal microscopy and compared before surgery, 1 month, and 3 months after surgery. Analysis of variance and t test were used for comparing the differences between different time points and two groups.

Results: Preoperatively and 1 month, 3 months postoperatively, the SNDs were (16 728.30 ± 4 300.30), (1 875.42 ± 300.50) and (1 701.55 ± 194.11) µm/mm(2) in the central cornea, (11 379.70 ± 1 833.92), (1 341.20 ± 288.68) and (1 860.87 ± 147.60) µm/mm(2) in the temporal cornea, and (8 506.79 ± 662.83), (7 428.96 ± 712.99) and (8 044.32 ± 1 077.54) µm/mm(2) in the nasal cornea, respectively, in the microkeratome group, and (16 351.59 ± 3 503.88), (1 859.38 ± 452.93) and (2 043.67 ± 377.76) in the central cornea, (12 328.22 ± 2 007.43), (1 483.85 ± 371.28) and (2 126.31 ± 279.87) µm/mm(2) in the temporal cornea, and (8 347.91 ± 789.44), (1 475.53 ± 293.98) and (2 022.10 ± 282.89) µm/mm(2) in the nasal cornea, respectively, in the femtosecond laser group. The SNDs at three positions all decreased significantly at each time point postoperatively compared to the baseline values in both groups (1 and 3 months in the microkeratome group: central t = 18.981 and 18.912, temporal t = 30.121 and 27.921, and nasal t = 6.456 and 2.126; in the femtosecond laser group: central t = 22.667 and 22.379, temporal t = 29.000 and 28.376, and nasal t = 46.329 and 41.751; all P < 0.01, except 3 months at the nasal in the microkeratome group, P = 0.042). The nasal SND increased significantly from month 1 to month 3 (t = -3.921, P < 0.01) in the microkeratome group, and the temporal and nasal SNDs both increased significantly from month 1 to month 3 (t = -9.629 and -6.645, both P < 0.01) in the femtosecond group. There were no significant differences in the central SND between the two groups (F = 0.002, P = 0.96). Significant differences were found in the nasal SND between the groups at 1 month and 3 months (t = 42.281 and 29.608, both P < 0.01), and in the temporal SND at 3 months after surgery (t = -4.595, P < 0.01).

Conclusions: Peripheral corneal nerve recovery occurred at 1 month after LASIK surgery. Patients with a femtosecond laser showed better corneal regeneration than those with a microkeratome.