Long-Term Clinical Comparison Of Five Klex Platforms: Visual, Refractive Outcomes, Higher-Order Aberrations, And Cap Thickness Accuracy

To compare 6-month clinical outcomes of keratorefractive lenticule extraction (KLEX) performed using five different femtosecond laser platforms (Zeiss VisuMax 500, Zeiss VisuMax 800, Johnson & Johnson ELITA, Schwind ATOS, and Ziemer Z8), focusing on visual recovery, refractive stability, higher-order aberrations (HoAs), and cap thickness accuracy and reproducibility.

NuneMiso Eye Center, Seoul, Republic of Korea

Patients who underwent KLEX using one of five different platforms were included and retrospectively analyzed. Postoperative uncorrected distance visual acuity (UDVA) was evaluated at 1 day, 1 week, 1 month, and 6 months. Manifest refraction (MR) was assessed at 1 and 6 months postoperatively. Corneal HoAs were analyzed using the Pentacam HR and Galilei G4 at 1 and 6 months. For cap thickness analysis, 30 eyes per platform were randomly selected. Planned cap thickness was compared with measured cap thickness obtained from anterior segment imaging. Cap accuracy was defined as the mean difference between planned and measured thickness, and reproducibility was assessed using the standard deviation and coefficient of variation.

Visual recovery on postoperative day 1 was significantly faster in the VisuMax 800 group; however, at 1 and 6 months, all groups demonstrated comparable outcomes. More than 95% of eyes in all groups were within ±0.50 diopters of the intended refractive target. Vertical coma was significantly higher in the VisuMax 500 group compared with the other platforms. Spherical aberration (SA) was lowest in the ATOS group, whereas total HoAs were lowest in the ELITA group. Cap thickness analysis demonstrated submicron-level precision in the Z8 and ELITA groups, both of which utilize flat applanation docking. The VisuMax system created deeper-than-intended caps, whereas the ATOS platform showed shallower cap formation relative to the planned thickness.

Long-term visual and refractive outcomes of newly introduced platforms were comparable to VisuMax systems and demonstrated stable results over 6 months. Differences in lenticule design and centration compensation functions of new platforms appeared to influence the induction of HoAs, potentially contributing to improvements in postoperative optical quality. Overall, cap thickness was formed with good accuracy across all platforms; however, systems utilizing flat docking demonstrated a tendency toward greater precision in cap thickness formation.