Abstract: Objective The aim of this trial was to compare the features of corneal flaps created using Ziemer LDV femtosecond laser and the Moria M2 microkeratome 90 ?滋m-knife. Design Prospective comparative case series.  Participants One hundred and seventy-six eyes of 88 patients were enrolled in this clinical trial. The patients were randomized divided into the Ziemer LDV femtosecond laser group and Moria M2 microkeratome 90 ?滋m-knife with matching demography. Methods Fourier-domain optical coherence tomography (RTVue OCT) was used to measure flap thickness using 28 settings on the 176 corneas at one week postoperatively. The features of the LASIK flaps were analyzed on the basis of the outcomes. Main Outcome Measures The thickness and shape of corneal flap. Results The mean flap thickness of the Ziemer LDV femtosecond laser group was considerably thinner than that of the Moria M2 microkeratome 90 ?滋m-knife group (106.03±6.64 ?滋m versus134.41±11.31 ?滋m) (P<0.01). The mean deviation between the achieved and attempted flap thickness was smaller in the Ziemer LDV group (7.15±4.89 ?滋m) than in the Moria M2 90 group (29.51±14.31 ?滋m) (P<0.01).  Conclusion The shape of flaps created using the Ziemer femtosecond laser is more uniform and closer to the expected thickness of 110 ?滋m than the ones created using the Moria M2 90 microkeratome. And Ziemer femtosecond laser should be the first choice for thin flap Lasik. (Ophthalmol CHN, 2013, 22: 261-265)

Key words:  laser in situ keratomileusis, flap thickness, Ziemer LDV femtosecond laser, microkeratome, Fourier-domain optical coherence tomography (OCT)