A Comparative Study of Laser In Situ Keratomileusis Flaps Created Using Single-Functional Versus Multifunctional Femtosecond Laser for Refractive Surgery

Abstract

Purpose: To compare laser in situ keratomileusis flaps created at the programmed target thickness of 120 μm using the LenSx multifunctional and the FS200 single-functional femtosecond lasers as evaluated by anterior segment optical coherence tomography (AS-OCT). Methods: This was a prospective, comparative, consecutive, blinded, nonrandomized study. Patients with stable refraction for over a year were consecutively allocated to the LenSx group or the FS200 group (n = 66; 33 patients in each group). All the patients underwent refractive surgery in both eyes. Previous eye surgery, ocular pathology associated with refractive errors, pregnancy, breastfeeding, and use of medication that causes ocular adverse effects constituted the exclusion criteria. Corneal topography, corneal tomography, dilated fundoscopy, applanation tonometry, ultrasonic pachymetry, dynamic and static refraction, visual acuity, and AS-OCT were evaluated before and after surgery. AS-OCT flap thickness was measured at 20 points on each cornea. Results: In the LenSx group, AS-OCT flap thickness differed significantly from the target thickness at 2 of 20 points (mean differences of 2.106 and 1.803 μm). In the FS200 group, 6 of 20 measurements differed significantly (mean differences ranging from 1.121 to 2.121 μm). The 2 lasers were similarly successful in creating regular and uniform flaps. The agreement between the 2 blinded examiners regarding the AS-OCT flap thickness measurements was excellent (intraclass correlation coefficient >0.75) in both groups. Conclusions: Both femtosecond lasers were safe and capable of creating highly reproducible, uniform, and regular flaps at the target preoperative thickness of 120 μm. The LenSx multifunctional femtosecond laser offers the advantage of allowing both cataract and corneal surgeries.

Corneal Lenticule Creation Using a New Solid-State Femtosecond Laser Measured by Spectral Domain OCT in a Porcine Eye Model

“…Similar results with excellent agreement of intended and measured cap thickness are shown by Reinstein et al 19 and Zhao et al 20 using the Visumax laser platform (Carl Zeiss Meditec) or for LASIK flaps with a deviation of less than 10 µm in eye bank corneas, 15 but some of those studies show a similar deviation but with a lower SD than in our data. A study by Colombo-Barboza was able to show a higher deviation from the intended measures for LASIK flaps but was significant at only 2 of 20 points measured, 21 and Parafita-Fernandez et al 22 had significantly thicker flaps than intended. Alio Del Barrio et al 23 found a thicker cap than expected created by the Visumax laser platform (Carl Zeiss Meditec), in contrast to fs flaps that were closer to the target thickness in the same trial, but Ozgurhan et al 24 reported that they did not find a significant deviation from intended cap thickness for either SMILE or fs-LASIK.…”