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Table 2 Parameters associated with posterior corneal elevation at 6-month and 5-year follow-up

From: Impact of ablation ratio on 5-year postoperative posterior corneal stability after refractive surgery: SMILE and FS-LASIK

Univariate analysis         Multivariate analysis       
6-month follow-up   PCE PTE PME 6-month follow-up PCE PTE PME
Parameters   Correlation coefficient P value Correlation coefficient P value Correlation coefficient P value Parameters Correlation coefficient P value Correlation coefficient P value Correlation coefficient P value
Sex Male −1.32 ± 3.01 < 0.05 −0.48 ± 2.74 < 0.05 −0.24 ± 1.85 0.98 Sex (Male vs. Female) −1.99 ± 0.74 0.01 −2.15 ± 0.72 0.003 NS 0.84
Female 1.13 ± 4.23 2.04 ± 4.32 −0.25 ± 1.93
Age ≥20 −2.00 ± 2.28 0.16 0.80 ± 1.64 0.09 −2.67 ± 3.21 0.13 Age 0.19 ± 0.07 0.003 0.19 ± 0.07 0.01 NS 1.00
21 ~ 30 0.05 ± 4.28 1.00 ± 4.30 −0.04 ± 1.97
31 ~ 40 0.67 ± 3.83 1.30 ± 3.72 −0.39 ± 1.54
≥41 3.50 ± 3.42 4.88 ± 3.94 −0.36 ± 1.66
Surgical group FS-LASIK 1.34 ± 4.21 0.23 2.09 ± 4.00 0.35 0.03 ± 1.88 0.04 Surgical group (SMILE vs. FS-LASIK) NS 0.26 NS 0.36 NS 0.42
SMILE 0.26 ± 4.21 1.23 ± 4.37 −0.82 ± 1.82
Ablation ratioa High-level 0.69 ± 4.43 0.87 1.69 ± 4.43 0.7 −0.35 ± 1.79 0.63 Ablation ratio NS 0.76 NS 0.82 NS 0.90
Low-level 0.55 ± 4.08 1.36 ± 4.14 −0.16 ± 1.98
5-year follow-up   PCE   PTE   PME   5-year follow-up PCE PTE PME
Sex Male 1.38 ± 4.97 0.6 2.07 ± 5.26 0.95 0.28 ± 2.26 0.38 Gender (Male vs. Female) NS 0.81 NS 0.90 NS 0.78
Female 0.76 ± 5.75 1.99 ± 6.20 −0.15 ± 2.25
Age ≥20 2.43 ± 3.55 0.23 3.57 ± 3.21 0.24 1.23 ± 1.90 < 0.001 Age NS 0.31 NS 0.28 −0.13 ± 0.04 0.001
21 ~ 30 1.46 ± 5.23 2.55 ± 5.70 0.44 ± 1.99
31 ~ 40 0.13 ± 4.16 1.39 ± 4.79 −0.59 ± 2.24
≥41 −1.73 ± 10.27 −1.00 ± 10.42 −2.35 ± 2.38
Surgical group FS-LASIK 1.63 ± 5.83 0.18 2.74 ± 6.13 0.22 −0.01 ± 2.21 0.83 Surgical group (SMILE vs. FS-LASIK) NS 0.75 NS 0.80 NS 0.88
SMILE 0.30 ± 5.25 1.42 ± 5.78 −0.01 ± 2.27
Ablation ratioa High-level 2.33 ± 4.68 < 0.05 3.38 ± 4.88 < 0.05 0.20 ± 2.03 0.25 Ablation ratio 2.68 ± 1.05 0.01 2.35 ± 1.17 0.04 NS 0.48
Low-level −0.56 ± 5.99 0.61 ± 6.64 −0.28 ± 2.40
  1. aHigh and low-level were divided by median ablation ratio in univariate analysis. Parameters with P value less than 0.1 in any one of follow-ups were entered into a multivariable analysis using generalized estimating equations. SMILE= small incision lenticule extraction; FS-LASIK=femtosecond laser-assisted in situ keratomileusis; PCE=posterior central elevation; PTE=posterior corneal surface at thinnest point; PME=posterior corneal mean elevation; NS=not significant. P values less than 0.05 were considered statistically significant