Comparative Assessment of 3 Techniques for LASIK Flap Creation
To measure the achieved versus the planned dimensions, calculate predictability values and compare the results of three different Laser in situ keratomileusis flap creation techniques.
Ninety eyes of 75 LASIK fit myopic patients 18 years or more of age were divided into three groups according to the method employed for creating the LASIK flap. Flap creation for group 1 (FS) (30 eyes of 15 patients) was done by the VisuMax 500 KHz femtosecond laser system, for group 2 (M2) (30 first operated eyes of 30 patients) by the Moria M2 mechanical microkeratome using the 130 µm single use head and for group 3 (SBK) (40 first operated eyes of 40 patients), by the Moria sub-Bowman's Keratomileusis one use plus 90µm head. Flap diameter and hinge chord length were measured using a marking caliper. Central and mid peripheral flap thickness were measured using the Visante anterior segment OCT.
- Flap Diameter: FS flaps were wider than planned by 0.453 ± 0.25 mm, M2 wider by 0.005 ± 0.31 mm and SBK wider by 0.202 ± 0.48 mm
- Flap Hinge chord length (HCL): FS had HCL longer than planned by 0.301 ± 0.53 mm, M2 shorter than planned by 0.703 ± 0.34 mm and SBK shorter than planned by 0.177 ± 0.66 mm
- Central flap thickness (CT): FS CT was thicker than planned by 7.567 ± 7.6 µm, M2 CT thicker by 18.6 ± 10.98 µm and SBK CT thicker by 11.167 ± 7.52 µm
- Mid-peripheral flap thickness (PT): FS PT was thicker than planned by 14.433 ± 7.06 µm, M2 PT thicker by 47.567 ± 14.51 µm and SBK PT thicker by 27.617 ± 6.6 µm
VisuMax Femtosecond laser produces relatively planar flaps as regards central and peripheral flap thickness with diameter and HCL significantly larger than planned. Moria M2 130µm single use heads produce meniscus flaps significantly thicker at periphery with predictable diameters and HCL less than planned. Moria SBK produces semi-planar flaps that have larger diameters and shorter HCL than planned.