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

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.

Reproducibility of laser in situ keratomileusis flap thickness using a new multifunctional femtosecond laser platform and correlation with clinical preoperative measurements.

PURPOSE: To analyze the reproducibility of laser in situ keratomileusis (LASIK) flap thickness (target 120 µm) using the multifunctional femtosecond laser (Lensx) and correlate postsurgical measurements with preoperative factors. SETTING: Hospital Oftalmológico Visão Laser, Santos, São Paulo, Brazil. DESIGN: Prospective case series. METHODS: Patients with stable refraction for over a year were evaluated. Patients who submitted to refractive surgery with -1.25 to -6.00 diopters (D), with or without astigmatism up to -4.00 D, and corneal curvature of 40.00 to 47.00 D were included. At 100 days postoperatively, an independent examiner performed 4 high-resolution tomographic sections of the cornea for each eye at 45- to 225-degree, 90- to 270-degree, 135- to 315-degree, and 0- to 180-degree meridians. Two masked experienced observers analyzed each section using measuring points located at the center of the cornea (0.0 mm), 2.0 mm to the left and to the right of the center, and 4.0 mm to the left and to the right of the center. RESULTS: The study comprised 33 patients (63 eyes), aged 21 to 50 years. A significant difference from the target flap thickness (120 µm) was found in 2 of 20 measurements; however, the actual difference was approximately 2.2 µm. Interrater reliability was excellent (ICC > 0.75), with an interrater bias close to 0. Clinical measurements were not predictive of the set of 20 postoperative measurements. CONCLUSION: Reproducibility of the multifunctional femtosecond laser was good for LASIK flap creation and no predictive correlation was found with preoperative clinical factors.