Corneal flap thickness with femtosecond laser-assisted SBK versus mechanical microkeratome-assisted SBK and postsurgical stability of the posterior corneal surface
Qiao Baodi,Tie Biao,Zhao Hong.
Department of Ophthalmology， the Second People′s Hospital of Zhengzhou， Zhengzhou 450006， China
Objective To compare the thickness of corneal flaps from femtosecond laser-assisted SBK versus mechanical microkeratome-assisted SBK and observe the stability of the posterior corneal surface. Methods This was a prospective nonrandom cohort study. The study included 200 patients （200 eyes） who underwent femtosecond laser-assisted SBK and 200 patients （200 eyes） who underwent mechanical microkeratome-assisted SBK from June 30 to December 31 in 2013 in the Second People′s Hospital of Zhengzhou. Corneal flap thickness， central curvature， highest curvature and vertex altitude of the posterior corneal surface were measured by A-scan ultrasound and Pentacam before surgery and 1 month， 3 months and 6 months after surgery. The results were compared between the two groups with an independent samples t-test. The data were compared at different time points with a repeated measure two-factor analysis of variance and an SNK-q test. Results The mean thickness of the mechanical microkeratome group was 104.4±10.3 µm， and the mean flap thickness of the femtosecond laser group was 99.2±5.1 µm. There was a significant difference between the two groups （t=5.365， P<0.05）. Absolute values of the differences between pre-surgical and postsurgical flap thickness were calculated， and the values for the mechanical microkeratome group and femtosecond laser group were 6.38±5.21 µm and 2.17±2.69 µm， respectively. There was a significant difference between the two groups （t=7.751， P<0.01）. Central curvature， the highest curvature and the vertex altitude of the posterior corneal surface were analyzed， and there were no significant differences at different time points or between femtosecond laser-assisted SBK and mechanical microkeratome-assisted SBK the two groups. Conclusion The thickness of corneal flaps have significant differences between curvatures and vertex altitude of the posterior corneal surface had good stability after the two surgery， and there was no significant difference in the influence that the two surgical methods had on the stability of the posterior corneal surface.
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