[Comparison of cornea flap made by femtosecond laser and microkeratome in laser in situ keratomileusis].

OBJECTIVE: To determine flap thickness variation in 110 µm thickness flap made by FS200 femtosecond laser and sub-Bowman keratomileusis (SBK) microkeratome for studying the potential factors that affect the flap thickness.

METHODS: It was a case-control study. Sixty patients were divided into two groups for laser in situ keratomileusis. The corneal flaps were made by using Alcon Wavelight FS200 femtosecond laser or MORIA SBK microkeratome. Central corneal flap thickness was calculated by subtraction pachymetry. Age, central corneal thickness (CCT), spherical equivalent refraction, mean keratometry and corneal diameter were recorded preoperatively for statistics.

RESULTS: This study comprised 120 eyes of 60 patients; 60 eyes were treated with each group. In Alcon Wavelight FS200 femtosecond laser group, the mean corneal flap thickness in the right and left eyes was (114.0 ± 6.6) and (111.4 ± 7.6) µm, respectively. The difference in corneal flap thickness between the right eye and the left eye (2.6 ± 9.1) µm was not statistically significant (t = 1.59, P = 0.12). Corneal flap thickness had no relationship with the age, preoperatively CCT, spherical equivalent refraction, corneal curvature and corneal diameter through stepwise regression analysis. In SBK microkeratome group, the mean corneal flap thickness in the right eye and the left eye was (110.6 ± 7.4) and (108.2 ± 6.1) µm respectively. The difference in corneal flap thickness between the right eye and the left eye (2.4 ± 6.6) µm was not statistically significant (t = 2.019, P = 0.054). Corneal flap thickness was positively correlated with preoperative CCT through stepwise regression analysis (r = 0.29, P = 0.021). Corneal flap thickness equaled to 67.77 + 0.076· CCT (F = 5.63, P = 0.021). Corneal flap thickness had no relationship with the age, spherical equivalent refraction, corneal curvature and corneal diameter.

CONCLUSIONS: Both FS200 femtosecond laser and SBK microkeratome can be used for making a good 110 µm thickness flap. Central corneal flap thickness was positively correlated with the preoperative CCT using the SBK microkeratome.