Reversing The Geometry: Contralateral-Eye Comparison Of Reverse‑Asymmetric Versus Asymmetric Klex With A Low-Energy Femtosecond Laser
Published 2026 - 44th Congress of the ESCRS
Reference: FP11.04 | Type: Free paper | DOI: 10.82333/2qdf-tg80
Authors: Mr Ivan Gabric* 1 , Dr Samuel Arba Mosquera 2 , Mr Filip Grulović 3 , Mr Ivan Samuel Modrić 3
1Refractive surgery,Eye Clinic Svjetlost,Zagreb,Croatia;Refractive surgery,Eye Clinic Svjetlost,Zagreb,Croatia, 2Refractive surgery,Schwind,Kleinostheim,Germany, 3Refractive surgery,Eye Clinic Svjetlost,Zagreb,Croatia
Purpose
To determine whether reverse‑asymmetric femtosecond spot–track geometry (spot 2.8 µm / track 6.0 µm) is clinically interchangeable with conventional asymmetric geometry (spot 6.0 µm / track 2.8 µm) for keratorefractive lenticule extraction (KLEx) using a low‑energy femtosecond laser set to 75nJ per pulse.
Setting
Single surgeon single center contralateral randomized study
Methods
Prospective contralateral-eye study of 82 eyes (41 patients) treated on a single platform (ATOS, Schwind). One eye received asymmetric geometry and the fellow eye reverse-asymmetric geometry. Outcomes at POD1, POW1, and POM1 included UDVA (logMAR), Micro-Aberration Scatter Index (MASI), and wavefront RMS (total HOAs, coma, spherical aberration) at 6-mm corneal and 4-mm ocular pupils. HOA change was calculated as Δ = post-op − pre-op at POW1 and POM1. Refractive predictability at POM1 was assessed using attempted vs achieved SEQ. Primary contrasts were paired differences. Holm–Bonferroni corrections were applied per endpoint family. UDVA equivalence was tested against ±0.05 logMAR (90% CIs).
Results
Preoperative demographics, refraction, pachymetry, and HOAs were comparable between geometries (n=41 pairs). UDVA did not differ at any visit (POD1, POW1, POM1; all P≥0.65). Paired UDVA differences remained non-significant after Holm correction, and 90% CIs at POD1 and POW1 were within ±0.05 logMAR, confirming equivalence. MASI showed no intergroup differences. After corneal wavefront trimming (|CW HOA|≤20 µm), paired Δ-HOA outcomes (total HOA, coma, spherical aberration) at 6-mm corneal and 4-mm ocular pupils were non-significant at POW1 and POM1. At POM1, refractive predictability was high and geometry-independent (~96% within ±0.50 D; 100% within ±1.00 D). No intraoperative complications occurred; no eye lost ≥1 line CDVA.
Conclusions
Reversing the spot–track orientation while maintaining same pulse power at 75nJ to 2.8/6.0 µm yields visual, optical, and refractive outcomes equivalent to the conventional 6.0/2.8 µm asymmetric geometry under Holm‑adjusted inference, with UDVA equivalence confirmed at POD1 and POW1. Given the shorter laser‑on time observed with the reverse‑asymmetric pattern, either geometry can be used interchangeably in low‑energy KLEx.