Femtosecond Laser Lasik Flap Thickness Variability The Retrospective Evaluation Of 5 Lasers: Intralase Fs60, Fs200, Ziemer Z6, Visuamax 500 And Visumax 800.

To evaluate programmed versus achieved laser-assisted in situ keratomileusis (LASIK) flap central thickness and investigate pachymetric flap thickness variability between 4 lasers.

Laservision Clinical and Research Institute, Athens, Greece

Flap thickness was investigated in 210 eyes that had had bilateral myopic LASIK. Group A (flaps made by the Abbott Medical Optics IntraLase™ FS60 femtosecond laser [Santa Ana, CA, USA] Group B (flaps made by the Alcon WaveLight(®) FS200 femtosecond laser [Fort Worth, TX, USA]), and Group C (Ziemer Z6 []) Group D (Visumax 500[Zeiss, Germany])and Group E(Visumax 800 [Zeiss, Germany]). Whole-cornea topographic maps of flap and epithelial thickness were obtained by scanning high-frequency ultrasound biomicroscopy. On each eye, topographic flap and epithelial thickness variability was computed by the standard deviation of thickness corresponding to 21 equally spaced points over the entire corneal area imaged.

The average central flap thickness for each group was 118.33 ± 5.38 μm (mean ± standard deviation) in Group A, 118.46 ± 7.72 μm in Group B, and 122.00 ± 7.64 μm in Group C 115.46 ± 5.72 μm, Group D 119.46 ± 8.72 μm and Group E 117.46 ± 6.72 μm. Topographic flap thickness variability was 5.73 ± 4.93 μm for Group A, 7.48 ± 4.23 μm for Group B, and 4.84 ± 1.88 μm for Group C, 7.82 ± 2.88 μm for Group D, and  6.24 ± 2.08 μm  for Group E. The smaller flap thickness variability of Group C (FS200) was statistically significant compared with all others (P = 0.4).

The five femtosecond lasers produced a reliable flap thickness and reduced variability than mechanical microkeratomes. In addition, our study suggests that there may be a difference in accuracy and topographic flap thickness variability between the results achieved by these femtosecond lasers examined.