Corneal Aberrations after ReLEx and Femtosecond Laser In Situ Keratomileusis for Moderate and High Myopia

Abstract

Purpose: : ReLEx is a new corneal refractive procedure, where a stromal lenticule is cut by a femto-second laser and manually extracted. The purpose of this study was to compare corneal higher-order aberrations after ReLEx and Femtosecond Laser In Situ Keratomileusis (FS-LASIK).

Methods: : Forty patients were treated with ReLEx and 41 patients with FS-LASIK in both eyes. The two groups were comparable with respect to preoperative BSCVA (≥ 0.8) and age. Preoperative spherical equivalent refraction averaged -7.5 D (range -4.5 D to -11.5 D) with a maximal astigmatism of -2.25 D. A Visumax femto-second laser (Carl Zeiss-Meditec, Jena, Germany) was used for ReLEx treatments and FS-LASIK flaps. In FS-LASIK, photoablation was performed with a MEL-80 excimer laser (Carl Zeiss-Meditec, Jena, Germany). Lenticule diameter was 6.5 mm in ReLEx, and ablation zone diameter was 6.0 mm in FS-LASIK. Flap thickness was 120 µm in all cases. BSCVA was measured before and 3 months after surgery, along with corneal tomography using an Oculus Pentacam-HR Scheimpflug camera. Corneal wavefront aberrations were calculated from the tomography data over the 4- and 6-mm-diameter central corneal zone and decomposed into Zernike polynomials up to the 8th order.

Results: : Preoperative corneal aberrations were similar in the two groups, and in both groups, 3^rd, 4^th, and other higher order aberrations increased after treatment. Three months after surgery there were significant differences in corneal higher-order aberrations between the groups at the 6 mm-diameter zone in the favor of ReLEx, i.e. lower spherical aberration (fourth order) and coma (third order). No significant difference was found with regard to trefoil (third order).BSCVA did not change preoperatively to 3 months after surgery in the two groups. A significantly greater proportion of ReLEx patients was within ± 1.0 D of the intended correction.

Conclusions: : Total corneal high-order aberrations increase after ReLEx and FS-LASIK for moderate and high myopia, but less in eyes treated with lenticule extraction compared to photoablation. BSCVA was unchanged, both after ReLEx and after FS-LASIK.

Keywords: refractive surgery • refractive surgery: optical quality