A Study Of Corneal Posterior Surface Elevation And Biomechanical Changes After Smile And Fs-Lasik In High Pta Patients: A Long-Term Observation

Published 2026 - 44th Congress of the ESCRS

Reference: PP10.03 | Type: Free paper | DOI: 10.82333/j7wx-bs31

Authors: Dr Yan Gao* ¹ , Mr Jianting Wang ²

¹Shanxi Eye Hospital,Taiyuan,China, ²Shanxi Medical University,Taiyuan,China

Purpose

To compare the differences in corneal posterior surface elevation and biomechanical changes two years after surgery between SMILE and FS-LASIK in high myopia patients with PTA ≥ 40%.

Setting

This prospective cohort study was conducted at the Refractive Surgery Center of Shanxi Eye Hospital, Taiyuan, China, from June to December 2023. Approved by the hospital’s Ethics Committee, all participants signed consent per the Declaration of Helsinki. Eligible patients were high myopes (-6.00 to -9.00 D SE, PTA ≥40%), SMILE and FS-LASIK were performed by experienced surgeons. Preoperative and 2-year postoperative corneal posterior elevation and biomechanical parameters were measured.

Methods

A prospective cohort study. The right eye data of of 58 patients who underwent refractive surgery were included for statistical analysis. The patients were divided into the SMILE group (29 eyes) and the FS-LASIK group (29 eyes) based on the surgical method. Preoperative SE was -6.00 D to -9.00 D. Using Pentacam and Corvis ST, corneal posterior surface elevation , including posterior central elevation, posterior elevation at the thinnest point , posterior maximum elevation, the mean posterior elevation in the central 2, 4, 6-mm area (MPE-2, 4, 6 mm) and biomechanical parameters (SP-A1, DA, IR, ARTH) were measured preoperatively and two years postoperatively. Change values for each parameter (Δ=postoperative - preoperative) were calculated.

Results

Baseline data of the two groups were matched preoperatively. Two years postoperatively, UCVA significantly improved in both groups. In the FS-LASIK group, MPE-2 mm decreased, while MPE-4,6 mm increased. PCE, PME and PTE all decreased. SP-A and ARTH decreased, DA and IR increased, all with statistical significance. In the SMILE group, except for MPE-2 mm and PCE, which had no statistically significant changes, the changing trends of the other values were the same as those in the FS-LASIK group. There were no statistical differences in ΔSP-A1, ΔDA, ΔIR, ΔARTH, ΔMPE-4, ΔMPE-6, ΔPTE, ΔPCE, ΔPME between the two groups (all P > 0.05). There were statistical differences in cutting depth, ΔMPE-2, and ΔPCE between the SMILE and FS-LASIK (P < 0.05).

Conclusions

Two years postoperatively, the uncorrected visual acuity of both groups showed significant improvement. For correcting high myopia with PTA ≥ 40%, SMILE and FS-LASIK show similar changes (Δ values) in the main corneal biomechanical parameters (SP-A1, DA, IR, ARTH) and most corneal posterior surface elevation parameters (except for MPE-2, PCE) two years after surgery. However, the SMILE technique demonstrates smaller changes in the corneal posterior surface elevation under deeper cutting, suggesting a potential advantage in maintaining the morphological stability of the corneal central area.