To investigate the impact of the ablation ratio on 5-year postoperative posterior corneal stability in myopic eyes after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery. A prospective, nonrandomized, cohort study: 80 eyes of 43 patients underwent SMILE surgery and 63 eyes of 32 patients underwent FS-LASIK surgery at the EYE & ENT Hospital, Fudan University. Ablation ratio was defined as lenticule thickness (SMILE cases) or ablation depth (FS-LASIK cases) divided by central corneal thickness (CCT). Posterior corneal elevation changes were recorded as posterior central elevation (PCE), posterior corneal surface at thinnest point (PTE) and posterior corneal mean elevation (PME). Patients were followed up at 6-month and 5-year interval to investigate the impact of the ablation ratio on posterior corneal elevation after SMILE and FS-LASIK surgery. PCE dropped at the 6-month follow-up for both SMILE (decreased by −1.11 ± 2.93 μm, P < 0.05) and FS-LASIK groups (decreased by −0.46 ± 3.72 μm, P < 0.05). PTE also dropped in SMILE (reduced by −2.04 ± 3.02 μm, P < 0.05) and FS-LASIK group (reduced by −1.28 ± 4.21 μm, P < 0.05) at the 6-month follow-up. Stable PCE (elevation change: SMILE −0.28 ± 4.03 μm; FS-LASIK 0.79 ± 4.13 μm, P > 0.05) and PTE (elevation change: SMILE −0.08 ± 4.28 μm; FS-LASIK 1.42 ± 3.85 μm, P > 0.05) for both groups were recorded at the 5-year follow-up compared to the 6-month visit. Ablation ratio was strongly correlated with 5-year postoperative PCE (β = 2.68 ± 1.05, P < 0.01) and PTE (β = 2.35 ± 1.17, P < 0.05). Cut-off value for 5-year postoperative raised PCE and PTE was 27.3 and 27.1%, respectively. Ablation ratio was strongly correlated with postoperative posterior corneal elevation in a 5-year follow-up in both SMILE and FS-LASIK groups. PCE and PTE underwent slight backward displacement 6-month postoperatively and remain stable at the 5-year follow-up. Threshold of the ablation ratio for resisting forward displacement of posterior corneal surface was 27.3 and 27.1% for SMILE and FS-LASIK groups, respectively.

中文翻译：

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消融率对屈光手术后5年术后角膜后稳定性的影响：SMILE和FS-LASIK

目的探讨小切口小孔摘除术（SMILE）和飞秒激光辅助原位角膜磨镶术（FS-LASIK）手术后近视眼术后5年术后角膜稳定性的消融率的影响。一项前瞻性，非随机队列研究：复旦大学眼与耳鼻喉科医院的43例患者的80眼进行了SMILE手术，32例患者的63眼进行了FS-LASIK手术。消融比定义为小透镜厚度（SMILE病例）或消融深度（FS-LASIK病例）除以中央角膜厚度（CCT）。角膜后高度的变化记录为后中央高程（PCE），最薄点后角膜表面（PTE）和角膜后平均高度（PME）。患者每隔6个月和5年进行一次随访，以研究消融率对SMILE和FS-LASIK手术后角膜后抬高的影响。SMILE组（减少-1.11±2.93μm，P <0.05）和FS-LASIK组（减少-0.46±3.72μm，P <0.05）在6个月随访中PCE下降。在6个月的随访中，SMILE的PTE也下降（降低了-2.04±3.02μm，P <0.05），而FS-LASIK组（降低了-1.28±4.21μm，P <0.05）。稳定的PCE（仰角变化：SMILE −0.28±4.03μm; FS-LASIK 0.79±4.13μm，P> 0.05）和PTE（仰角变化：SMILE −0.08±4.28μm; FS-LASIK 1.42±3.85μm，P> 0.05）两组的随访均为5年，而6个月为随访。消融率与术后5年PCE密切相关（β= 2.68±1.05，P <0。01）和PTE（β= 2.35±1.17，P <0.05）。术后5年PCE和PTE升高的临界值分别为27.3％和27.1％。在SMILE和FS-LASIK组的5年随访中，消融率与术后角膜后高度明显相关。术后6个月PCE和PTE发生轻微的向后移位，并在5年的随访中保持稳定。对于SMILE组和FS-LASIK组，抵抗后角膜表面向前移位的消融率阈值分别为27.3％和27.1％。术后6个月PCE和PTE发生轻微的向后移位，并在5年的随访中保持稳定。对于SMILE组和FS-LASIK组，抵抗后角膜表面向前移位的消融率阈值分别为27.3％和27.1％。术后6个月PCE和PTE发生轻微的向后移位，并在5年的随访中保持稳定。对于SMILE组和FS-LASIK组，抵抗后角膜表面向前移位的消融率阈值分别为27.3％和27.1％。