Evaluation of morphological features: femtosecond-LASIK flap vs. SMILE cap, and the effects on corneal higher-order aberrations

Xiaoying He; Qin He; Minjie Yuan; Zhi Fang; Kai Zhang; Tiepei Zhu; Wei Han

doi:10.1007/s00417-022-05841-0

Evaluation of morphological features: femtosecond-LASIK flap vs. SMILE cap, and the effects on corneal higher-order aberrations

Graefes Arch Clin Exp Ophthalmol. 2022 Dec;260(12):3993-4003. doi: 10.1007/s00417-022-05841-0. Epub 2022 Sep 27.

Authors

Xiaoying He^#¹, Qin He^#², Minjie Yuan¹, Zhi Fang¹, Kai Zhang¹, Tiepei Zhu¹, Wei Han³

Affiliations

¹ Department of Ophthalmology, Eye Center of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China.
² Department of Ophthalmology, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China.
³ Department of Ophthalmology, Eye Center of the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China. hanweidr@zju.edu.cn.

^# Contributed equally.

PMID: 36166075
DOI: 10.1007/s00417-022-05841-0

Abstract

Purpose: The aim of this study is to evaluate morphological features of corneal flap/cap and the correlations with corneal higher-order aberrations (HOAs) changes after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE).

Methods: This was a retrospective study. Pre- and postoperative (1 and 3 months) corneal HOAs were assessed with Pentacam HR. The corneal flap/cap thickness at 32 points (± 1.5 mm, ± 2 mm, ± 2.5 mm, and ± 3 mm from the corneal vertex on meridian 0°/45°/90°/135°) were measured using anterior segment optical coherence tomography at 3 months postoperatively. Morphological features of corneal flap/cap including predictability (P), uniformity (U), and symmetry (S) were calculated and used for correlation analysis with corneal HOAs changes.

Results: Eighty-six eyes (44 patients) and ninety-six eyes (50 patients) were involved in FS-LASIK and SMILE groups, respectively. Significant thicker corneal flap/cap than the predicted was observed at each measuring point and meridian in both groups (difference > 2.225 μm, the within-subject standard deviation over 6-mm optical zone). There was no statistically significant difference in predictability of corneal flap/cap thickness, while U_{6 mm} (P < .0001), U₀ (P < .001), U₄₅ (P = .002), U₉₀ (P < .0001), U₁₃₅ (P = .004), S_{6 mm} (P < .0001), S₀ (P < .001), and S₉₀ (P < .0001) over 6 mm zone were less in SMILE than in FS-LASIK. The changes of corneal tHOAs, Z (3, - 1), Z (3, 1), and SA were significantly correlated with morphological features of corneal flap/cap.

Conclusion: Both FS-LASIK and SMILE had good predictability in flap or cap thickness, while the uniformity and symmetry of SMILE cap were better than FS-LASIK flap. The quality of flap/cap was closely associated with the changes of corneal HOAs.

Keywords: Corneal cap; Corneal flap; Femtosecond laser in situ keratomileusis; Higher-order aberrations; Small incision lenticule extraction.

MeSH terms

Cornea / surgery
Corneal Stroma / surgery
Humans
Keratomileusis, Laser In Situ* / methods
Lasers, Excimer / therapeutic use
Myopia* / diagnosis
Myopia* / surgery
Prospective Studies
Retrospective Studies
Visual Acuity