Verification and measurement of the side-cut angle of corneal flap in patients undergoing LASIK surgery using FS 200 kHz femtosecond laser system versus conventional mechanical microkeratome

Introduction: This is a prospective nonrandomized interventional clinical trial conducted to measure and verify the intended versus the achieved LASIK flap side-cut angle in two groups of patients, Femtosecond laser-assisted in-situ keratomileusis (FS-LASIK) using Wavelight FS200 (Alcon Laboratories Inc. Fort Worth, TX, USA) and the conventional mechanical microkeratme (Moria M(2) 90). Methods: This prospective clinical trial was conducted on 40 eyes of 20 patients (20 eyes in each group) in the interval between December 2017 and August 2018. Heidelberg anterior segment OCT was done for the patients 2 weeks postoperatively to measure the corneal flap side cut angle. Results: The achieved side-cut angles of all the patients in the first group (the femtosecond laser-assisted in-situ keratomileusis group) were equal to or more inverted than the intended angle (110–115°) in all the study candidates with a minimum angle (110°) and maximum angle (155°). Unlike the achieved side-cut angle in the second group (the mechanical microkeratome group) in which all the achieved side-cut angle were acute with a minimum angle (30°) and maximum angle (65°) which is more acute than the intended side-cut angle (70°). Conclusion: In our study we found that the femtoLASIK technology was capable of making the flap side-cut angle more obtuse than the intended angle, unlike the achieved flap side-cut angle done using the mechanical microkeratome which was more acute than the intended angle in 100% of cases.