| Purpose: This study aims to evaluate short-term and long-term outcomes of astigmatic correction following small incision lenticule extraction(SMILE) with the use of vector method; to compare the correction of low to moderate astigmatism between SMILE and femtosecond laser assisted laser in-situ keratomileusis(FS-LASIK) and the correction of moderate to high astigmatism between SMILE and wavefront-guided laser in-situ keratomileusis(WG-LASIK). Methods: Retrospective study. Ninety-eight patients(98 eyes) were enrolled to accept SMILE. The observations of visual acuity and manifest refraction were followed preoperatively and at 1 month, 6 months and 12 months. Fifty-one patients(95 eyes) underwent SMILE and 40 patients(69 eyes) underwent FS-LASIK with low to moderate myopic astigmatism. Twenty-two patients(42 eyes) had SMILE and 12 patients(22 eyes) had WG-LASIK with moderate to high myopic astigmatism. Alpins' s vector analysis was used to calculate the target induced astigmatism(TIA), surgically induced astigmatism(SIA), and difference vector(DV). The correction index(CI), index of success(IOS), magnitude of error(Mof E), angle of error(Aof E) and flattening index(FI) were used to indicate the correction of astigmatism. Safety efficacy indexes were used to evaluate the recovery of visual acuity. Comparisons between surgeries were analyzed with independent-sample t test or Mann-Whitney test. Pearson or Spearman rank correlation coefficients were applied to indicate the association between each parameter. Results: 1. The mean astigmatism in vector form was-0.14 D × 27.19° at 1 month,-0.13 D × 27.29° at 6 months, and-0.10 D × 28.63° at 12 months after SMILE. No significant difference of refraction was found between follow-ups. 2. Significant negative correlations were found between CI and the magnitude of preoperative astigmatism(P < 0.05), and positive correlations were found between IOS and absolute Aof E value at each follow-up(P < 0.01). 3. Mean astigmatism was-0.02 D × 172.98° after SMILE and-0.02 D × 49.27° after FS-LASIK. Postoperative sphere and SE were lower in SMILE(P < 0.05). 4. The CI were(0.97 ± 0.16) and(1.03 ± 0.23) after SMILE and FS-LASIK, the FI were(0.96 ± 0.16) and(1.03 ± 0.24) after SMILE and FS-LASIK, respectively. Statistical significances were observed in above parameters(P < 0.05). 5. The mean astigmatism in vector form was-0.32 D × 177.3° after SMILE and-0.26 D × 2.2° after WG-LASIK without significant difference. 6. For the correction of moderate astigmatism, the mean astigmatism was-0.20 D × 174.3° after SMILE and-0.11 D × 84.8° after WG-LASIK. Significant difference was found in CI between SMILE and WG-LASIK(P < 0.05). 7. For the correction of high astigmatism, the mean astigmatism was-0.42 D × 178.6° after SMILE and-0.51 D × 1.1° after WG-LASIK. CI was(0.88 ± 0.12) after SMILE and(0.87 ± 0.13) after WG-LASIK without statistical significance. Conclusions: 1. Vector method could describe and evaluate the correction of astigmatism accurately in corneal refractive surgery. 2. SMILE surgery was effective and safe in correcting myopic astigmatism, and stable refractive outcomes were observed at long-term follow-up. 3. SMILE and FS-LASIK were effective to correct low to moderate astigmatism. Significant difference was found in axial direction, but not in residual diopters. 4. SMILE and WG-LASIK could achieve preferable outcomes. However, undercorrection was obvious found after both procedures for high astigmatism. 5. Quantitative error and axial error could have an effect on the correction of astigmatism. Quantitative error could be one of the major factors for the undercorrection of high astigmatism. |
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