<p>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</p>

Abstract

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.

Creation of a Corneal Flap for Laser In Situ Keratomileusis Using a Three-Dimensional Femtosecond Laser Cut: Clinical and Optical Coherence Tomography Features

“…The angle of the side cut achieved using femtosecond LASIK has only been evaluated in a study with another laser platform; the effective side cut angle diverged significantly from the programmed angle, with a mean difference of 25 • [7]. In our series, the achieved angle was, instead, both accurate and precise.…”

“…Precise side cut angles induce different biomechanical properties in the cornea [5,6]. However, in some laser platforms the effective angle of the side cut may considerably differ from the programmed angle, even by 45 • , and with a high standard deviation [7], thus rendering the induced benefits unpredictable.…”

“…There has not, however, been a study to verify the effective side cut angle achieved using this new application nor the possible additional time under suction required to perform a 3D flap. Anterior segment optical coherence tomography (OCT) is the ideal imaging technique to depict the corneal details after laser surgery [7,8]; we, therefore, compared 2D-and 3D-generated LASIK flaps in a large series using the new software, to assess the (1) mean time of suction, (2) mean effective angle of the side cut on OCT, and (3) intraoperative and early postoperative complications. Anterior segment optical coherence tomography (OCT) is the ideal imaging technique to depict the corneal details after laser surgery [7,8]; we, therefore, compared 2Dand 3D-generated LASIK flaps in a large series using the new software, to assess the (1) mean time of suction, (2) mean effective angle of the side cut on OCT, and (3) intraoperative and early postoperative complications.…”

Comparison of 9.0 and 9.2 mm Flap Diameter Options of Femtosecond Laser In-Situ Keratomileusis for Hypermetropia and Hypermetropic Astigmatism

“…Femtosecond laser technology has decreased the time spent in cutting the flap, which can be made more accurately and at a more predictable depth than those created by mechanical microkeratomes, and thus has improved the quality of the stromal bed [4, 9]. In addition, a customized corneal flap configuration can be provided by femtosecond laser technology in many directions [3–5,9]. Flap thickness is one of the most important parameters, and a previous study has shown that many complications including corneal haze, flap tear, bubble escape, free flap, flap fold, diffuse lamellar keratitis, and epithelial ingrowth occur more commonly in thin flaps [10].…”

“…Nowadays, femtosecond LASIK is a widely performed procedure all over the world [3]. The creation of the epithelial-stromal flap is one of the most crucial steps in LASIK surgery, and femtosecond laser provides corneal flap configuration by changing the morphology, depth, and diameter, thereby refining the postoperative results, which have been studied in recent years [5–8].…”