+1 Recommend
0 collections
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

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


      Read this article at

          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.



          To evaluate the refractive outcomes for the correction of low to moderate astigmatism up to 1 year following small incision lenticule extraction (SMILE) surgery.


          This 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.


          The 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.


          SMILE 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.

          Related collections

          Most cited references29

          • Record: found
          • Abstract: found
          • Article: not found

          Results of small incision lenticule extraction: All-in-one femtosecond laser refractive surgery.

          To report the clinical results of small incision lenticule extraction to correct refractive errors using a femtosecond laser to refine the femtosecond lenticule extraction technique. Private laser center, Vadodara, India. Prospective clinical study. The VisuMax femtosecond laser system was used to perform small incision lenticule extraction to treat refractive errors. The laser was used to cut a refractive lenticule intrastromally to correct myopia and myopic astigmatism. The lenticule was then extracted from the stroma through a 3.0 to 5.0 mm incision. Outcome measures were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), and manifest refraction during 6 months of follow-up. Corneal topography and ocular wavefront aberrations were also measured. The study enrolled 51 eyes of 41 patients. The mean spherical equivalent was -4.87 diopters (D) ± 2.16 (SD) preoperatively and +0.03 ± 0.30 D 6 months postoperatively. Refractive stability was achieved within 1 month (P<.01). Six months after surgery, 79% of all full-correction cases had a UDVA of 20/25 or better. The 6-month postoperative CDVA was the same as or better than the preoperative CDVA in 95% of eyes. Two eyes lost 1 line of CDVA. All-in-one femtosecond refractive correction using a small incision technique was safe, predictable, and effective in treating myopia and myopic astigmatism. No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
            • Record: found
            • Abstract: found
            • Article: not found

            Safety and complications of more than 1500 small-incision lenticule extraction procedures.

            To evaluate the safety and complications of small-incision lenticule extraction (SMILE). Clinical control cohort study. A total of 922 healthy patients (1800 eyes) who were treated for myopia or myopic astigmatism between January 2011 and March 2013 at the Department of Ophthalmology, Aarhus, Denmark. Patients received a full preoperative examination and were treated with SMILE in both eyes and followed for 3 months (1574 eyes). Patients with complications, including loss of corrected distance visual acuity (CDVA) or dissatisfaction, were offered a late reexamination. Surgical complications and CDVA. Mean preoperative spherical equivalent refraction was -7.25±1.84 diopters (D). Average postoperative refraction was -0.28±0.52 D, and mean error of treatment was -0.15±0.50 D. By 3 months, 86% (1346 eyes) had unchanged or improved CDVA. A loss of 2 or more lines was observed in 1.5% of eyes; however, at a late follow-up visit (average, 18 months), CDVA was within 1 line of the preoperative level in all eyes. Perioperative complications included epithelial abrasions (6%), small tears at the incision (1.8%), and difficult lenticule extraction (1.9%). The cap was perforated in 4 eyes, and a major tear occurred in 1 eye; however, none of these patients had late visual symptoms. In 0.8% (14 eyes), suction was lost during surgery. Re-treatment was successful in 13 eyes, whereas 1 eye had ghost images and was re-treated with topography-guided photorefractive keratectomy (PRK). Postoperative complications included trace haze (8%), epithelial dryness on day 1 (5%), interface inflammation secondary to central abrasion (0.3%), and minor interface infiltrates (0.3%); these complications had an impact on CDVA at 3 months in only 1 case. Irregular corneal topography occurred in 1.0% of eyes, resulting in reduced 3-month CDVA (12 eyes) or ghost images (6 eyes). Topography-guided PRK was performed in 4 eyes, with improvement in 3 cases. Satisfaction was high, with only 2 patients dissatisfied at their latest visit because of blurred vision or residual astigmatism. Overall, SMILE had acceptable safety. Although 1.5% of eyes had reduced CDVA by 3 months, visual acuity was restored in the long term. Likewise, patient satisfaction was high. Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
              • Record: found
              • Abstract: found
              • Article: not found

              Mathematical model to compare the relative tensile strength of the cornea after PRK, LASIK, and small incision lenticule extraction.

              To develop a mathematical model to estimate the relative differences in postoperative stromal tensile strength following photorefractive keratectomy (PRK), LASIK, and small incision lenticule extraction (SMILE). Using previously published data where in vitro corneal stromal tensile strength was determined as a function of depth, a mathematical model was built to calculate the relative remaining tensile strength by fitting the data with a fourth order polynomial function yielding a high correlation coefficient (R(2) = 0.930). Calculating the area under this function provided a measure of total stromal tensile strength (TTS), based only on the residual stromal layer for PRK or LASIK and the residual stromal layers above and below the lenticule interface for SMILE. Postoperative TTS was greatest after SMILE, followed by PRK, then LASIK; for example, in a 550-μm cornea after 100-μm tissue removal, postoperative TTS was 75% for SMILE (130-μm cap), 68% for PRK, and 54% for LASIK (110-μm flap). The postoperative TTS decreased for thinner corneal pachymetry for all treatment types. In LASIK, the postoperative TTS decreased with increasing flap thickness by 0.22%/μm, but increased by 0.08%/μm for greater cap thickness in SMILE. The model predicted that SMILE lenticule thickness could be approximately 100 μm greater than the LASIK ablation depth and still have equivalent corneal strength (equivalent to approximately 7.75 diopters). This mathematical model predicts that the postoperative TTS is considerably higher after SMILE than both PRK and LASIK, as expected given that the strongest anterior lamellae remain intact. Consequently, SMILE should be able to correct higher levels of myopia. Copyright 2013, SLACK Incorporated.

                Author and article information

                BMC Ophthalmol
                BMC Ophthalmol
                BMC Ophthalmology
                BioMed Central (London )
                24 January 2015
                : 15
                : 8
                Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, No.4 Gansu Rd, Heping District, Tianjin, 300020 China
                © Zhang et al.; licensee BioMed Central. 2015

                This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                : 12 June 2014
                : 15 January 2015
                Research Article
                Custom metadata
                © The Author(s) 2015

                Ophthalmology & Optometry
                vector analysis,astigmatism,femtosecond laser,small incision lenticule extraction,refractive surgery,long-term


                Comment on this article