Vector analysis of low to moderate astigmatism with small incision lenticule extraction (SMILE): results of a 1-year follow-up

Abstract

BackgroundTo evaluate the refractive outcomes for the correction of low to moderate astigmatism up to 1 year following small incision lenticule extraction (SMILE) surgery.MethodsThis retrospective study enrolled 98 eyes from 98 patients who underwent SMILE surgery for the correction of myopia and astigmatism. Only right eyes were included in this study to avoid the bias of orientation errors. The vector method was used to analyze the outcomes of astigmatism at 1 month, 6 months and 12 months after the procedure, including the double-angle plots, correction index (CI), index of success (IOS), angle of error (AofE) and magnitude of error (MofE). The effectiveness, safety, stability and predictability were also investigated during the 12-month follow-up.ResultsThe preoperative cylinder ranged from -2.75 D to -0.25 D (average of -0.90 ± 0.68 D), and the mean postoperative cylinder values were -0.24 ± 0.29 D, -0.24 ± 0.29 D, and -0.20 ± 0.27 D at 1 month, 6 months, and 12 months, respectively. 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 surgery. The CI was 1.00 ± 0.32 and IOS was 0.29 ± 0.44 at the 12-month follow-up. Significant negative correlations were found between the CI and absolute target induced astigmatism (TIA) value, and positive correlations were found between the IOS and absolute AofE value (P < 0.05). The MofE was limited within ±1.00 D at the 12-month follow-up. Fifty-six eyes (57.1%) gained one line in corrected distance visual acuity (CDVA) and five eyes (5.1%) gained two lines. There were no significant differences observed in the refractive outcomes among time points.ConclusionsSMILE surgery was effective and safe in correcting low to moderate astigmatism, and stable refractive outcomes were observed at the long-term follow-up. The undercorrection of astigmatism could possibly be influenced by attempted astigmatism correction preoperatively, the axis rotation during the surgery or wound healing postoperatively. This study suggested that nomograms should be adjusted in correcting astigmatism with SMILE surgery.

Early outcomes after small incision lenticule extraction and photorefractive keratectomy for correction of high myopia

“…Ivarsen and Hjortdal reported that undercorrection of astigmatism increased with attempted treatment following SMILE16. Undercorrection of astigmatic error has been reported in previous studies comparing SMILE to other corneal refractive surgeries8171819. The CI was very close to 1.0 for SMILE in our cohort, representing accurate astigmatic correction.…”

Comparison of Moderate- to High-Astigmatism Corrections Using WaveFront–Guided Laser In Situ Keratomileusis and Small-Incision Lenticule Extraction

“…For low to moderate astigmatism, a previous study revealed that SMILE was an effective, safe, and stable procedure, despite having a tendency for slight undercorrection. 23 High astigmatism was considerably undercorrected after both surgical procedures. The unmodified nomogram might be one of the potential factors and could result in undercorrection.…”

Matched population comparison of visual outcomes and patient satisfaction between 3 modalities for the correction of low to moderate myopic astigmatism

“…Pedersen et al have shown significant undercorrection of cylinder with SMILE over time 20. This was mainly attributed to non-compensation of errors of cyclotorsion and non-application of nomograms during the procedure 12. However, excellent results for astigmatism treatment were observed with ReLEx SMILE, which were far better compared to the published literature on SMILE.…”

“…Data from various studies suggest that this modality is a safe and effective method to correct varying degrees of myopia, with the advantages of minimum postoperative discomfort and restrictions, less dry eye, and probably better biomechanics compared to LASIK 9,10. Studies comparing the results of astigmatism correction with ReLEx SMILE and LASIK, however, showed better outcomes with LASIK, most likely due to non-availability of iris registration and eye tracker in the current version of the femtosecond laser used for the ReLEx SMILE procedure 11,12. However, similar comparison studies have not been reported between T-ICL and ReLEx SMILE.…”