Clinical Outcomes of SMILE With a Triple Centration Technique and Corneal Wavefront-Guided Transepithelial PRK in High Astigmatism

Epithelial thickness map-adjusted transepithelial photorefractive keratectomy for treatment of myopic astigmatism: 12-month results

PURPOSE

To evaluate the refractive results of Transepithelial Photorefractive Keratectomy (t-PRK) with the Technolas Teneo2 Excimer laser platform.

METHODS

In this retrospective comparative interventional case series, a total of 199 patients with myopia ranging from - 1 to - 7 diopters were enrolled and separated into three groups based on their target refraction of zero (group 1), - 0.25 (group 2), and - 0.5 diopters (group 3), respectively. The main outcome measure was post-operative cycloplegic refraction. Trans-PRK was performed using the Technolas Teneo2 Excimer laser. To prevent any remaining epithelium during stromal ablation, we adopted the thickest epithelial point in the 7 mm central map as the reference for Phototherapeutic keratectomy (PTK) depth. Patients were examined three and twelve months after the procedure, and the results were analyzed.

RESULTS

At the 12-month follow-up, uncorrected distance visual acuity was 20/20 in all patients. However, there was a significant difference in cycloplegic spherical equivalent refraction between the three groups. The 12-month post-operative spherical equivalent refraction was 0.90 ± 0.33 D, 0.79 ± 0.26 D, and 0.60 ± 0.19 D in groups 1, 2, and 3, respectively (P < 0.001; Kruskal-Wallis test). The rates of spherical equivalent refraction of more than 0.75 D were 58.3%, 39.1%, and 9.1% in the 0 D, - 0.25 D, and -0.50 D groups, respectively (P < 0.001; Chi-squared test).

CONCLUSIONS

The t-PRK with Technolas Teneo2 Excimer laser and epithelial thickness map adjustment of PTK induce a significant amount of residual hyperopia (> 0.75 D) in a large proportion of eyes with a target refraction of 0 or - 0.25, which is significantly reduced by using a target refraction of - 0.5.

Association of myopia and astigmatism with postoperative ocular high order aberration after small incision lenticule extraction

OBJECTIVE

To investigate the correlation between higher-order aberrations (HOA) after small incision lenticule extraction (SMILE) and the severity of myopia and astigmatism, along with the relevant factors. These findings will provide valuable insights for decreasing the occurrence of HOA after SMILE and enhancing visual quality.

METHODS

A total of 75 patients (150 eyes) with myopia and astigmatism who underwent SMILE were categorized into four groups based on the severity of myopia and astigmatism: Myopia Group 1 (Group M1, spherical diopter ranged from -1.00 D to -4.00 D), Myopia Group 2 (Group M2, spherical diopter ranged from -4.10 D to -10.00 D), Astigmatism Group 1 (Group A1, cylindrical diopter ranged from 0 D to -1.00 D), and Astigmatism Group 2 (Group A2, cylindrical diopter ranged from -1.10 D to -3.00 D). A comprehensive assessment was performed to examine the association between HOA and various relevant factors, including a detailed analysis of the subgroups.

RESULTS

Group M1 had significantly lower levels of total eye coma aberration (CA), corneal total HOA (tHOA), internal tHOA, and vertical CA ( Z 3 - 1 ) after SMILE than Group M2 (P < 0.05). Similarly, Group A1 had significantly lower levels of total eye tHOA, CA, trefoil aberration (TA), corneal tHOA, TA, and vertical TA ( Z 3 - 3 ) after SMILE than Group A2 (P < 0.05). Pearson correlation analysis indicated a statistically significant positive relationship between the severity of myopia/astigmatism and most HOA (P < 0.05). Subgroup evaluations demonstrated a notable increase in postoperative HOA associated with myopia and astigmatism in Groups M2 and A2 compared with the control group. Lenticule thickness, postoperative central corneal thickness (CCT), postoperative uncorrected distance visual acuity (UDVA), and postoperative corneal Km and Cyl were strongly correlated with most HOA. Age, eyes, and postoperative intraocular pressure (IOP) were only associated with specific HOA.

CONCLUSION

HOA positively correlated with the severity of myopia and astigmatism after SMILE. However, this relationship was not linear. HOA after SMILE was influenced by various factors, and additional specialized investigations are required to establish its clinical importance.

Effect of Cyclotorsion Compensation in Small Incision Lenticule Extraction Surgery for the Correction of Myopic Astigmatism: A Systematic Review and Meta-Analysis

INTRODUCTION

Small incision lenticule extraction (SMILE) has made notable advancements in addressing myopic astigmatism. Nevertheless, the potential impact of cyclotorsion on surgical outcomes cannot be overlooked. This study aims to assess the effectiveness of cyclotorsion compensation technology in SMILE surgery for the correction of myopic astigmatism, examining its influence on postoperative visual quality.

METHODS

A systematic review and meta-analysis were conducted. A comprehensive literature search was performed using databases, including PubMed, Web of Science, EMBASE, Cochrane Library, EBSCO, Scopus, CNKI, VIP, and Wan Fang. Studies meeting the criteria were selected and included. Data were independently extracted by three authors. Clinical outcome parameters were analyzed using Review Manager version 5.3.

RESULTS

This meta-analysis included ten studies. The results showed that, compared with the control group (cyclotorsion compensation was not performed in SMILE), the following indicators in the cyclotorsion compensation group were: residual astigmatism (RA) [weighted mean difference (MD) = 0.73, 95% confidence interval (CI) + 0.26 to + 1.19, P = 0.002], spherical equivalent (SE) (MD = 1.99, 95% CI + 0.77 to + 3.21, P = 0.001), coma (MD = -0.06, 95% CI -0.08 to -0.04, P < 0.00001), higher-order aberrations (HOAs) (MD = -0.04, 95% CI -0.06 to -0.02, P < 0.0001), follow-up 6-month angle of error (AE) (MD = -2.67, 95% CI -3.71 to -1.63, P < 0.00001), and follow-up 6-month uncorrected distance visual acuity (UDVA) (MD = -0.05, 95% CI -0.08 to -0.01, P = 0.005), and the differences in results were statistically significant. However, the differences among correction index, index of success (IOS), targeted induced astigmatism (TIA), magnitude of error (ME), and spherical aberration (SA) were not statistically significant.

CONCLUSION

Cyclotorsion compensation proves to be effective and predictable for correcting myopic astigmatism. The cyclotorsion compensation group demonstrated advantages over the control group in terms of postoperative residual astigmatism, and it induced fewer coma aberrations. Whether cyclotorsion compensation can lead to better visual quality remains to be seen, and further research on correcting myopic astigmatism through cyclotorsion compensation is warranted.

Differences in ocular high order aberrations before and after small incision lenticule extraction for correction of myopia: a systematic review and meta-analysis

Objective

To examine the causes and factors that lead to high order aberration (HOA) during the treatment of myopia using small incision lenticule extraction (SMILE), as well as the differences between SMILE and other corneal refractive surgeries through a systematic review and meta-analysis.

Methods

A systematic search was conducted from January 2015 to February 2023 in Pubmed, Embase, Web of Science, and Google Scholar databases to gather relevant studies on SMILE and HOA. Studies meeting specific criteria were chosen, and clinical data was retrieved for analysis.

Results

This meta-analysis resulted in the inclusion of 19 studies involving 1,503 eyes. Pooled results showed significant induction of total HOA (tHOA, d = -0.21, p < 0.001), spherical aberration (SA, d = -0.11, p < 0.001) and coma aberration (CA, d = -0.18, p < 0.001) after SMILE compared to pre-SMILE, while no significant change in trefoil aberration (TA) was observed (d = -0.00, p = 0.91). There was a significantly lower induction of tHOA after SMILE compared to femtosecond laser-assisted in situ keratomileusis (FS-LASIK, d = 0.04, p < 0.001), and no significant difference was observed compared to wavefront aberration-guided (WFG) refractive surgery (d = 0.00, p = 0.75). There was also a significant association between different levels of myopia and astigmatism, duration of follow-up, lenticule thickness, and preoperative central corneal thickness (CCT) on the induction of tHOA after SMILE (p < 0.05), while the higher preoperative myopia group (sphere > -5D), lower preoperative astigmatism group (cylinder ≤ -1D), larger lenticule thickness group (lenticule thickness > 100 μm), shorter follow-up group (follow-up 1 month postoperatively) and the thicker CCT group (CCT > 550 μm) brought a significant induction of tHOA compared to the opposite comparison group (p < 0.001).

Conclusion

While SMILE can induce HOA significantly, it induces less HOA than FS-LASIK. Postoperative HOA following SMILE can be affected by factors such as myopia, astigmatism, lenticule thickness, CCT, and duration of follow-up. Future research should continue to explore techniques to decrease the induction of HOA by using this methodology.

Systematic review registration

https://www.crd.york.ac.uk/prospero/.

Three-Month Clinical Outcomes to Correct Myopia or Myopic Astigmatism Using a Femtosecond Laser for Lenticule Creation With Automated Centration and Cyclotorsion Compensation

PURPOSE

To individually evaluate the clinical outcomes for right and left eyes in the first 3 months after laser-assisted lenticule extraction for myopia and myopic astigmatism with the use of the new ATOS femtosecond laser system (Smart-Sight; SCHWIND eye-tech-solutions).

METHODS

A total of 331 eyes from 168 patients (166 right eyes and 165 left eyes) consecutively treated with SmartSight lenticule extraction were retrospective analyzed after a 3-month follow-up period. Patients' mean age was 26 ± 6 years (range: 18 to 47 years) and mean preoperative spherical equivalent (SEQ) was -5.07 ± 1.92 diopters [D] (range: -1.50 to -11.25 D) with a mean astigmatism of -1.04 ± 0.85 D (range: 0.00 to -4.00 D). At 3 months of follow-up, visual acuity, SEQ and cylinder, safety index, efficacy index, corneal higher order aberrations, and intraocular pressure (IOP) were analyzed. Furthermore, refractive and visual outcomes were also analyzed for the right and left eyes individually. All lenticule extraction treatments were performed with the SmartSight treatment method of the SCHWIND ATOS femtosecond laser.

RESULTS

At 3 months after surgery, mean SEQ was -0.12 ± 0.19 D and 98% of eyes were within ±0.50 D of the SEQ. All eyes were within ±1.00 D of the SEQ. Astigmatism of 0.50 D or less was achieved in 99% of eyes. The change in Snellen lines (difference between preoperative corrected distance visual acuity and postoperative uncorrected distance visual acuity) showed a gain of one or more lines in 13% and in 85% of the eyes the same was achieved. There was a loss of one or more lines at 3 months of follow-up in 1.6%. The safety index was 1.03 and efficacy index was 1.02. No significant difference between the right and left eyes was found.

CONCLUSIONS

The 3-month follow-up data show that SmartSight treatment for correction of myopia and myopic astigmatism with the SCHWIND ATOS is a safe, efficient, and accurate procedure. It provided excellent results in terms of visual recovery, predictability, and higher order aberrations. [J Refract Surg. 2024;40(1):e30-e41.].

Comparison of myopic astigmatic correction after cross-assisted SMILE, FS-LASIK, and transPRK

PURPOSE

To compare astigmatic correction among cross-assisted small-incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and transepithelial photorefractive keratectomy (transPRK).

SETTING

The Eye Hospital of Wenzhou Medical University, Zhejiang, China.

DESIGN

Prospective comparison study.

METHODS

154 right eyes of 154 patients with astigmatism of -1.00 to -2.75 diopters (D) were included in this study. 64 eyes, 42 eyes, and 48 eyes were receiving SMILE, FS-LASIK, and transPRK, respectively. The SMILE group used cross-axial alignment for head positioning for astigmatism correction. In the FS-LASIK and transPRK groups, static and dynamic cyclotorsion control were used. Changes in ocular parameters and vector analysis were assessed at 6 months postoperatively.

RESULTS

The safety and efficacy indices were comparable among the 3 groups at 6 months postoperatively. Residual astigmatism was smallest in the SMILE group (-0.23 ± 0.25 D) compared with that in FS-LASIK (-0.40 ± 0.28 D, P = .009) and transPRK groups (-0.42 ± 0.32 D, P = .001). 53 (82.8%), 36 (85.7%), and 37 (77.1%) eyes achieved an angle of error within ±5 degrees, respectively ( P = .55). Notably, vector analysis showed that the difference vector, the magnitude of the error, and its absolute value were significantly smaller in the SMILE group than those in the other groups ( P < .05). In addition, the higher-order aberrations, especially coma, were significantly induced postoperatively in each group ( P < .001).

CONCLUSIONS

Residual astigmatism magnitude was smallest by cross-assisted SMILE, followed by FS-LASIK and transPRK, and the astigmatism axial correction was comparable among groups.

Vector analysis of astigmatism correction after PRK, FS-LASIK, and SMILE for myopic astigmatism

PURPOSE

To compare astigmatic correction among photorefractive keratectomy (PRK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and small-incision lenticule extraction (SMILE).

METHODS

This prospective study enrolled 157 eyes that underwent three procedures (59 PRK, 47 FS-LASIK, and 51 SMILE) for the treatment of myopia with low to high astigmatism (- 0.25 to - 4.50 D). Ocular residual astigmatism (ORA) was calculated by vector analysis using refractive (RA) and corneal astigmatism. Vector analysis results were compared in different procedures in the two RA groups (low ≤ 1.00 D and high > 1.00 D) at 3 and 12 months postoperatively.

RESULTS

There were no significant between-group differences in postoperative safety and efficacy outcomes (all P > 0.05). No significant differences were found in postoperative cylinders between all surgical groups (all p > 0.05), except for 3 months postoperative ORA in FS-LASIK (P = 0.004). At 12 months, 77%, 59.2%, and 50% of eyes attain emmetropia in the FS-LASIK, SMILE, and PRK groups, respectively. Vector analysis showed comparable values for surgical induced astigmatism, target induced astigmatism, mean error, and angle of error between groups at 12 months. Significant differences were observed only in the correction index and difference vector parameters in the astigmatic > 1.00 D group at 3 months (P < 0.001), and FS-LASIK was preferable.

CONCLUSIONS

One-year outcomes revealed that PRK, FS-LASIK, and SMILE were all equally effective in correcting myopic astigmatism. However, FS-LASIK demonstrated more favorable astigmatism correction in eyes with astigmatism > 1.00D in early postoperatively.

Method to determine the centration of a lenticule of tissue extracted from a cornea

A simple and novel method to analyse the centration of a lenticule of tissue extracted from a cornea has been developed, in which the centre of "mass" of the individual differences between post and preoperative maps of several corneal metrics represents the lenticule centration and its spatial distance to a reference point (aimed centration) determines the decentration. Different parameters have been evaluated to weight the centre of "mass". The robustness of the methods has been evaluated using perturbation analysis (adding white-noise to the data) based on realistic uncertainties. A clipped analysis has been performed to prevent large, localised areas of lacking/missing data from affecting the centre of "mass". The method has been tested on a pilot cohort of clinical data showing 30% and 63% of the treatments within 200 µm of decentration for corneal thickness and refractive equivalent power, respectively. Except for anterior elevation with a total standard deviation of 17 µm, all other metrics show excellent precision of ∼5 µm. The method provides a reliable and objective way to determine the centration of a lenticule of tissue extracted from a cornea and it can be applied to any topo- or tomographic derived metric.

Comparative analysis of visual outcomes following small-incision lenticule extraction with or without cyclotorsion compensation in eyes with high astigmatism: Contralateral eye study

Purpose

To compare the visual outcomes in patients undergoing small-incision lenticule extraction (SMILE) for correction of myopic astigmatism (≥-1.50 D) with or without manual cyclotorsion compensation.

Methods

A prospective, double-blinded, randomized, contralateral study was conducted in the refractive services of a tertiary eye care center. Eligible patients with bilateral high myopic astigmatism (≥1.5 D) and intraoperative cyclotorsion (≥5°) undergoing SMILE between June 2018 and May 2019 were included. Cyclotorsion compensation was performed using triple centration method before femtosecond laser delivery. Uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) measurement, manifest refraction, slit-lamp biomicroscopy, and corneal tomography were performed preoperatively and at 1 and 3 months' postoperative visit. Astigmatic outcomes were analyzed using Alpins criteria.

Results

A total of 30 patients (60 eyes) were included in this study. The patients underwent bilateral SMILE surgery, with manual cyclotorsion compensation in one eye (CC group, n = 30 eyes) and no cyclotorsion compensation in the other eye (NCC group, n = 30 eyes). Preoperative astigmatism and intraoperative cyclotorsion were -2.0 D and 7.03° ± 1.06° (CC) and -1.75 D and 7.24° ± 0.98° (NCC) (P = 0.472 and 0.240, respectively). No significant differences were noted in mean refractive spherical equivalent (MRSE), UDVA, CDVA, and refractive error between the two groups at 3 months' postoperative visit. Astigmatic outcomes measured using Alpins criteria demonstrated no significant difference between the two cohorts.

Conclusion

The cyclotorsion compensation technique provided no additional advantage in terms of astigmatic outcomes or postoperative visual quality, in eyes with high preoperative astigmatism and intraoperative cyclotorsion.

Methods of Corneal Vertex Centration and Evaluation of Effective Optical Zone in Small Incision Lenticule Extraction

Inappropriate small incision lenticule extraction (SMILE) centration methods can affect the decentration of the effective optical zone (EOZ) after operation, which can subsequently lead to the decline of postoperative visual quality. We aimed to provide an overview of corneal vertex (CV) centration methods and an evaluation of the size and decentration of the EOZ in SMILE. We described the CV centration methods for patients with myopia, myopic astigmatism, hyperopia, and large kappa angle. The measurement methods of the EOZ were evaluated from the aspects of corneal morphology and corneal refractive power. Additionally, we summarized the advantages and disadvantages of measuring decentration based on topographic mapping and intraoperative video-captured images. Finally, we discussed the relationship between the EOZ and visual quality. Based on our review, clinicians should consider the following when choosing CV centration methods and evaluating EOZ postoperatively. First, the tear film mark center or topographic map comparison method is preferred for the correction of myopia, low myopic astigmatism, hyperopia, and large kappa angle (>0.2 mm). Triple marking centration is recommended for high myopic astigmatism (-3.5 diopters). Second, the total corneal power better reflects the change in refractive power than the topographic method. The measurement of the area rather than the diameter of the total corneal refractive power is more suitable for the evaluation of noncircular EOZs after high myopia astigmatism (<-2.0 diopters). Third, for the evaluation of decentration, the tangential curvature difference map method is preferred as it is not influenced by offset pupils. Finally, a large EOZ after SMILE may improve patient tolerance to decentration.

The 18-Month Outcomes of a Contralateral, Randomized, Prospective Clinical Trial Comparing Photorefractive Keratectomy and SMILE for Myopia

PURPOSE

To compare clinical outcomes and patient satisfaction of photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) for myopia.

METHODS

This contralateral, randomized, prospective clinical trial included 86 eyes of 43 patients diagnosed as having spherical equivalent (SE) from -1.00 to -8.00 diopters (D). One eye of each patient was randomly allocated to receive either PRK with 0.02% mitomycin C or SMILE. Visual acuity measurement, slit-lamp microscopy, manifest and cycloplegic refraction, Scheimpflug corneal tomography, contrast sensitivity assessment, ocular wavefront aberrometry, and a satisfaction questionnaire were performed preoperatively and during an 18-month follow-up.

RESULTS

Forty-three eyes of each group completed the study. After 18 months of follow-up, eyes treated with PRK and SMILE showed comparable results regarding uncorrected distance visual acuity (-0.12 ± 0.07 and -0.25 ± 0.09, respectively), safety, efficacy, contrast sensitivity, and ocular wavefront aberrometry. For predictability, eyes treated with PRK had a statistically lower residual spherical equivalent when compared with eyes treated with SMILE. Residual astigmatism of 0.50 D or less was achieved in 95% of the PRK group and 81% of the SMILE group. At the 1-month follow-up visit, the PRK group presented worse evaluation in relation to vision and foreign body sensation when compared to the SMILE group.

CONCLUSIONS

Both PRK and SMILE presented as safe and effective strategies for treating myopia with comparative clinical results. Eyes treated with PRK showed lower spherical equivalent and residual astigmatism. In the first month, eyes treated with SMILE showed less foreign body sensation and faster visual recovery. [J Refract Surg. 2023;39(3):180-186.].

Efficacy of small-incision lenticule extraction surgery in high astigmatism: A meta-analysis

Purpose

This study aimed to evaluate the efficacy of small-incision lenticule extraction (SMILE) in improving vision and visual quality and correcting astigmatism for the treatment of high astigmatism.

Methods

Eligible studies and studies comparing the efficacy of SMILE with femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) or transepithelial photorefractive keratectomy (T-PRK) for high astigmatism (≥2.00 D) were identified in PubMed, Embase, and the Cochrane Central Register of Controlled Trials, searched from their inception to 29 May 2022. The references of all searched studies were checked as supplements. The risk of bias was evaluated for each eligible study. The literature was screened according to the inclusion and exclusion criteria, and relative data were extracted. Data were extracted and analyzed by ReviewManager 5.4. The primary outcome was post-operative uncorrected distance visual acuity (UDVA). The secondary outcomes included corneal aberrations and vector parameters. The weight mean difference (WMD) and their 95% confidence intervals (95% CI) were used to assess the strength of the association.

Results

A total of six studies including 380 astigmatism eyes were involved, with 211 high-astigmatism eyes and 31 low-astigmatism eyes undergoing SMILE surgery, 94 high-astigmatism eyes undergoing FS-LASIK surgery, and 44 high-astigmatism eyes undergoing T-PRK surgery. Compared with non-SMILE, SMILE induced more astigmatism (weighted mean difference [WMD] = -0.07, 95% CI [-0.12 to -0.02], P = 0.005) and fewer sphere aberrations (WMD = -0.12, 95% CI [-0.17 to -0.08], P < 0.00001). The post-operative UDVA, sphere, spherical equivalent (SE), and higher order aberrations in different surgeries were likewise equivalent. The difference vector and index of success were significantly higher, and the surgically induced astigmatism vector, correction index, and magnitude of error were significantly lower in SMILE.

Conclusion

This meta-analysis suggests that SMILE, FS-LASIK, and T-PRK show excellent efficacy, predictability, and safety for myopia. SMILE exhibited less astigmatism refraction predictability and less surgically induced spherical aberrations. There may be more under-correction in SMILE. More randomized, prospective, and large sample-sized studies are needed to confirm these conclusions in the long term.

Effect of keratometric astigmatism on visual outcomes following small incision lenticule extraction

Purpose

To investigate the influence of keratometric astigmatism on visual outcomes following small incision lenticule extraction (SMILE).

Methods

Eighty eyes undergoing SMILE for myopia correction were classified into two groups based on preoperative keratometric astigmatism: low keratometric astigmatism (LA) and high keratometric astigmatism (HA) groups. Refractive outcomes, vector components, and changes in higher order aberrations (HOAs) were evaluated preoperatively and 6 months postoperatively.

Results

At the postoperative 6-month visit, no significant difference was observed in the decentered distance between the HA and LA groups (HA: 0.17 ± 0.08 mm, LA: 0.16 ± 0.08 mm, P = 0.189). No significant differences in the correction index (P = 0.481), absolute angle of error (P = 0.104), or index of success (P = 0.147) were observed between the two groups. There was no significant difference in the induction of corneal aberrations between the two groups. Furthermore, there were no significant associations between the decentered distance and the vector components of astigmatic correction or induction of higher-order aberration in the HA group (P ≥ 0.294, P ≥ 0.112) or the LA group (P ≥ 0.323, P ≥ 0.080).

Conclusions

SMILE for high keratometric astigmatism could achieve comparable treatment centration and visual quality to that of low keratometric astigmatism

Clinical outcomes of the immediate reapplication of small-incision lenticule extraction without adjusting the surgical parameters after suction loss

This study was to analyze the clinical outcomes of immediate reapplication of small-incision lenticule extraction (SMILE) without adjusting the surgical parameters after suction loss and to compare the outcomes with contralateral eyes that underwent uneventful SMILE. A total of 74 patients who underwent uneventful SMILE in one eye (Uneventful group) and immediate reapplication of SMILE without adjusting the surgical parameters after suction loss in the contralateral eye (Suction loss group) were included. Suction loss occurred during the posterior lenticule surface cut in 39 eyes (53%) and the cap cut in 35 eyes (47%). Surgical outcomes, including visual acuity, manifest refraction, keratometry, and corneal wavefront aberrations, were evaluated at 6 months postoperatively. The mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and spherical equivalent were − 0.02 ± 0.07, − 0.04 ± 0.04, and − 0.10 ± 0.46 diopters (D), respectively, in the Suction loss group and − 0.02 ± 0.07, − 0.04 ± 0.05, and − 0.19 ± 0.53 D, respectively (P = 0.965, 0.519, and 0.265, respectively), in the Uneventful group. Changes between the preoperative and 6-month postoperative total corneal aberrations, spherical aberrations, and horizontal and vertical coma did not significantly differ between the Suction loss and Uneventful groups. Immediate reapplication of SMILE without adjusting the surgical parameters after suction loss resulted in good surgical outcomes that were comparable with those of uneventful SMILE.

Comparison of Visual Outcomes and Optical Quality of Femtosecond Laser-Assisted SMILE and Visian Implantable Collamer Lens (ICL V4c) Implantation for Moderate to High Myopia: A Meta-analysis

PURPOSE

To compare visual outcomes and optical quality of femtosecond laser-assisted small incision lenticule extraction (SMILE) and Visian Implantable Collamer Lens (ICL V4c; STAAR Surgical) implantation for moderate to high myopia.

METHODS

For this systematic review and meta-analysis, the Cochrane, PubMed, Embase, and Chinese databases (Wan-fang data and CNKI) were comprehensively searched to identify studies comparing SMILE and ICL V4c implantation. Data of interest were extracted and analyzed by Stata V.16.0 software (StataCorp). The weighted mean differences and their 95% confidence intervals were used to assess the strength of the association.

RESULTS

Twelve studies incorporating 1,390 eyes of 822 patients were included. The analysis revealed ICL V4c implantation had a significantly higher safety index and lower high order aberrations, coma, and spherical aberration than SMILE in treating moderate to high myopia (P < .05). Subgroup analysis revealed such differences were more prominent in patients with high myopia who had shorter follow-up duration. When follow-up was longer than 6 months, the differences in safety index and total HOAs became nonsignificant (P > .05). The two procedures had no difference in efficacy index, postoperative visual acuity, spherical equivalent, trefoil, Objective Scatter Index, or modulation transfer function cut-off frequency (P > .05).

CONCLUSIONS

Both SMILE and ICL V4c implantation were safe and efficient for moderate to high myopia. Compared with SMILE, ICL V4c implantation might provide better postoperative visual quality in patients with high myopia in the early postoperative period. [J Refract Surg. 2022;38(6):332-338.].

Vector analysis of high astigmatism (≥ 2.0 diopters) correction after small-incision lenticule extraction with stringent head positioning and femtosecond laser-assisted laser in situ keratomileusis with compensation of cyclotorsion

Background

The purpose of this study was to compare the astigmatic correction by vector analysis in patients with high myopic astigmatism after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) with cyclotorsion compensation or small-incision lenticule extraction (SMILE) with stringent head positioning.

Setting

Beijing Aier-Intech Eye Hospital, Beijing, China.

Design

A retrospective case series.

Methods

Patients who had correction of myopic astigmatism of 2 diopters (D) or more treated with either FS-LASIK with cyclotorsion compensation or SMILE with stringent head positioning were included. The results of vision and refraction were analyzed and compared between groups with the right eye.

Results

The study enrolled 94 patients (41eyes in an FS-LASIK with compensation of cyclotorsion group and 53 eyes in a SMILE with stringent head positioning control group. The mean preoperative manifest cylinder was -2.65 ± 0.77D in the FS-LASIK group and 2.51 ± 0.56D in the SMILE group (P = 0.302). At 12 months, there was no significant between-group difference in uncorrected distance visual acuity (UDVA, P = 0.274) and postoperative spherical equivalent (SEQ) (P = 0.107). 46.3% and 24.5% of eyes in the FS-LASIK and SMILE groups were within 0.25 D were within 0.25D postoperative cylinder, respectively, and 78% and 66% of eyes in these two groups were within 0.5 D postoperative cylinder (P = 0.027, P = 0.202). The vector analysis showed comparable between-group target-induced astigmatism (TIA) (P = 0.114), surgically induced astigmatism (SIA) (P = 0.057), difference vector (DV, P = 0.069), and the angle of error (AE) (P = 0 .213) values. The index of success (IOS) was 0.18 in the FS-LASIK group and 0.24 in the SMILE group (P = 0.024), with a significant difference between the two groups.

Conclusion

FS-LASIK with compensation of cyclotorsion showed a favorable correction of high myopic astigmatism (≥ 2.0 D) compared to SMILE with stringent head positioning at 12 months.

Comparison of clinical outcomes of LASIK, Trans-PRK, and SMILE for correction of myopia

Transepithelial photorefractive keratectomy (Trans-PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) are three mainstay refractive surgeries worldwide. The applicability, efficacy, safety, and predictability of these different techniques are quite similar. Trans-PRK has the strongest biostability, earliest return to normal corneal sensitivity but the longest recovery time, most uncomfortable postoperative experience, and possibility of corneal haze. LASIK possesses the fastest visual rehabilitation but the slowest corneal nerve reinnervation, and flap displacement is possibly lifelong. SMILE incurs no flap-related complications and has intermediate vision recovery time and biomechanics compared with Trans-PRK and LASIK. However, it lacks the cyclotorsion-compensation system, eye-tracking system, and customized treatment profile for high astigmatism or irregular corneal surface. This review aims to introduce the mechanisms, pros, and cons of these three types of refractive surgery. With full understanding, practitioners could advise patients on the most suitable treatment of choice.

Comparison of small incision lenticule extraction and transepithelial photorefractive keratectomy in terms of visual quality in myopia patients

PURPOSE

To comprehensively compare visual quality between small incision lenticule extraction (SMILE) and transepithelial photorefractive keratectomy (tPRK).

METHODS

Sixty-four eyes in the SMILE group and 42 eyes in the tPRK group were enrolled in this study. In both groups, visual acuity, manifest refraction, higher-order aberrations (HOAs), contrast sensitivity (CS) at four spatial frequencies (3, 6, 12, 18 c/d) under three conditions (photopic, low glare, high glare), the cut-off value of the modulation transfer function (MTFcut-off), the objective scatter index (OSI) and the Strehl ratio (SR) were measured preoperatively and 1, 3 and 6 months postoperatively.

RESULTS

At 6 months postoperatively, the SMILE and tPRK groups showed similar safety, efficacy and predictability. Additionally, MTFcut-off, SR and OSI exhibited comparable results. In contrast, the photopic area under the logarithm of the CS function (AULCSF) showed better outcomes in the tPRK group than in the SMILE group (SMILE versus tPRK: 1.21 ± 0.10 versus 1.25 ± 0.09, p = 0.014). Furthermore, the induced coma aberrations were larger in the SMILE group (SMILE versus tPRK: 0.10 ± 0.16 versus 0.06 ± 0.12, 95% CI [0.08, 0.31], p < 0.0001).

CONCLUSIONS

Both SMILE and tPRK obtained comparable visual quality at 6 months postoperatively, accompanied by better photopic CS and smaller induced coma aberrations with tPRK. Paying more attention to alignment or developing a centration technique would be beneficial for visual quality when performing SMILE.

Comparison of refractive and visual outcomes between image-guided assisted small incision lenticule extraction and wavefront-optimized femtosecond laser in situ keratomileusis in treatment of high astigmatism

PURPOSE

To compare refractive and visual results of image-guided assisted small-incision lenticule extraction (IGA-SMILE) and wavefront-optimized femtosecond laser in situ keratomileusis (FS-LASIK) in the treatment of high astigmatism.

SETTINGS

Osmangazi Aritmi Hospital, Bursa, Turkey.

DESIGN

Retrospective.

METHODS

This retrospective case-matched study included 64 eyes that had undergone IGA-SMILE and 64 eyes that had undergone wavefront optimized FS-LASIK. The mean preoperative myopia and astigmatism were -4.05 ±1.98 diopter (D) and 3.11 ±1.06 D in the IGA-SMILE group and -4.21 ±2.23 D and -3.15 ±0.62 D in the FS-LASIK group. One year later, visual and refractive results were compared in the groups. Vector analysis based on Alpins method was done to evaluate astigmatic treatment.

RESULTS

At one year, the residual astigmatism was -0.21 ± 0.25 D in the IGA-SMILE and -0.21 ± 0.24 D in the FS-LASIK group (p=0.305). In the IGA-SMILE group, 57 (89.1%) eyes achieved uncorrected distance visual acuity (UDVA) of 20/20 or better, as did 56 (85.9%) eyes in the FS-LASIK group. Vector analysis results demonstrated that the difference vectors were 0.22 ±0.24 D and 0.21 ±0.22 D (p=0.230), the correction indexes were 0.95 ±0.08 and 0.95 ±0.08 (p=0.239), the indices of success were 0.08 ±0.09 and 0.08±0.09 (p=0.248), in the IGA-SMILE and the FS-LASIK groups, respectively.

CONCLUSION

The combination of an image-guided system with SMILE resulted in high efficacy and safety indices that were comparable to FS-LASIK surgery.

Comparison of Clinical and Biomechanical Outcomes of Small Incision Lenticule Extraction With 120- and 140-µm Cap Thickness

Purpose

The purpose of this study was to compare the clinical outcomes and corneal biomechanical changes between 120-µm and 140-µm cap thickness after small incision lenticule extraction (SMILE).

Methods

This prospective study included 150 eyes (150 patients: 91 eyes in the 120-µm group, and 59 eyes in the 140-µm group) who underwent SMILE. Enhanced correction nomograms were applied for patients according to cap thickness. Clinical outcomes, including visual acuity, refraction, and corneal wavefront aberrations, were compared between the two groups. Corneal biomechanics were evaluated using the Corvis ST (Oculus, Wetzlar, Germany).

Results

The mean uncorrected-distance visual acuity, safety and efficacy indices, and refractive predictability were comparable in the 120-µm and 140-µm groups after SMILE. The postoperative total corneal root mean square higher-order aberrations (HOAs) and spherical aberrations was 0.48 ± 0.31 and 0.26 ± 0.10 in the 120-µm group, and 0.53 ± 0.16 and 0.34 ± 0.13 in the 140-µm group, which showed significant differences between the two groups (P = 0.027, and <0.001, respectively). Although corneal stiffness decreased after SMILE in both groups, the changes in the deformation amplitude ratio were significantly higher in the 140-µm group than in the 120-µm group (P = 0.022).

Conclusions

SMILE with 120-µm and 140-µm cap thickness provided excellent predictable outcomes according to our enhanced correction nomogram. The amount of tissue removal required to achieve the same amount of refractive correction was greater in the thicker cap group. The induction of corneal HOAs and weakening of corneal biomechanics were less pronounced in the thin-cap group, which may be associated with the thinner cap, lesser lenticule thickness, or thicker residual stromal bed.

Translational Relevance

Although SMILE with different cap thickness was effective, thicker lenticule thickness in the thick-cap group may be associated with induction of HOAs, and corneal stiffness changes.

Comparison of clinical outcomes between vector planning and manifest refraction planning in SMILE for myopic astigmatism

PURPOSE

To compare clinical outcomes of small-incision lenticule extraction (SMILE) between manifest refraction (MR) and vector planning for myopic astigmatism with high ocular residual astigmatism (ORA).

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea.

DESIGN

Prospective, randomized, comparative case series.

METHODS

Patients with myopic astigmatism and ORA of 0.75 diopters (D) or greater were randomized into the MR or vector planning group and underwent SMILE without applying any nomogram for cylinder correction. Visual acuity, MR, corneal topography, and corneal aberration were measured preoperatively and postoperatively. Outcomes at 6 months postoperatively were compared between the groups.

RESULTS

The study comprised 114 patients (114 eyes): 58 eyes in MR planning and 56 eyes in vector planning. The mean uncorrected and corrected distance visual acuity, safety and efficacy indices were comparable between the 2 groups. Postoperative refractive cylinder reached statistically significant differences between the groups (-0.22 ± 0.18 D and -0.14 ± 0.16 D in the MR and vector planning groups, respectively, P = .02). Postoperative corneal toricity and ORA reached statistically significant lower in the vector planning group.

CONCLUSIONS

In myopic astigmatism with high ORA, MR and vector planning in SMILE were effective with comparable visual outcomes; vector planning showed statistically significant lower postoperative refractive and corneal astigmatism and ORA. Use of vector planning may improve refractive outcomes in SMILE cases with high ORA. However, the results may have been different had a nomogram adjustment been applied, as is often used for cylinder corrections with SMILE.

Three-Month Outcomes of Myopic Astigmatism Correction With Small Incision Guided Human Cornea Treatment

PURPOSE

To evaluate refractive and visual outcomes of small incision guided human cornea treatment (SmartSight; SCHWIND eye-tech-solutions) in the treatment of myopic astigmatism with the use of a new femtosecond laser system.

METHODS

This retrospective, observational case series study included 104 eyes of 56 patients who underwent SmartSight to correct myopic astigmatism and completed the 3-month follow-up. Procedures were performed with a SCHWIND ATOS femtosecond laser.

RESULTS

Preoperatively, mean manifest spherical equivalent refraction was -6.12 ± 1.99 diopters (D) (range: -3.00 to -11.50 D) and astigmatism was 1.02 ± 0.56 D (range: 0.25 to 2.75 D). Three months postoperatively, it was +0.47 ± 0.32 D (range: -0.75 to +1.00 D) and 0.27± 0.22 D (range: 0.00 to 0.75 D), respectively (both P < .05). Spherical equivalent correction within ±0.50 D was achieved in 62 eyes (60%), and cylindrical correction in 90 eyes (87%). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 94 eyes (90%) and postoperative uncorrected distance visual acuity was 20/20 or better in 96 eyes (92%). No eye lost two or more Snellen lines of CDVA.

CONCLUSIONS

Myopic astigmatism correction with Smart-Sight provided good results for efficacy, safety, predictability, and visual outcomes in the first 3 months of follow-up. [J Refract Surg. 2021;37(5):304-311.].

Clinical Outcomes of Small Incision Lenticule Extraction in Myopia: Study of Vector Parameters and Corneal Aberrations

PURPOSE

To investigate clinical outcomes of small incision lenticule extraction (SMILE) including vector parameters and corneal aberrations in myopic patients.

METHODS

This retrospective, observational case series included 57 eyes (29 patients) that received treatment for myopia using SMILE. Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1 and 3 months after surgery. We analyzed the safety, efficacy, vector parameters, and corneal aberrations at 3 months after surgery.

RESULTS

Preoperatively, mean manifest refraction spherical equivalent refraction was -4.94 ± 1.94 D (range, -8.25 to 0 diopters [D]), and the cylinder was -1.14 ± 0.82 D (range, -3 to 0 D). Mean manifest refraction spherical equivalent improved to -0.10 ± 0.23 D at 3 months postoperatively, when uncorrected distance visual acuity was 20 / 20 or better in 55 (96%) eyes. The linear regression model of target induced astigmatism vector versus surgically induced astigmatism vector exhibited slopes and coefficients (R²) of 0.9618 and 0.9748, respectively (y = 0.9618x + 0.0006, R² = 0.9748). While total corneal root mean square higher order aberrations, coma and trefoil showed statistically significant increase, spherical aberration did not show statistically significant change after SMILE.

CONCLUSIONS

SMILE has proven to be effective and safe for correcting myopia and astigmatism. We showed that SMILE did not induce spherical aberrations. A small increase in postoperative corneal higher order aberration may be associated with increase in coma and trefoil.

Evaluation of preoperative corneal astigmatism using swept-source optical biometry in Chinese cataract surgery candidates with high myopia: a prospective, comparative observational study

Background

High myopia and cataracts are major causes of blindness in East and Southeast Asia. Corneal astigmatism is a major contributor to uncorrected poor vision after cataract surgery in patients with high myopia. The purpose of the present study was to evaluate the demographic characteristics and distribution of preoperative corneal astigmatism in Chinese cataract surgery candidates with high myopia.

Methods

Swept-source optical coherence tomography-based optical biometry was performed preoperatively in consecutive cataract surgery candidates who were classified by axial length (AL) into a high myopia group (defined as AL ≥26.0 mm) and a control group (normal ALs). The demographics, ALs, and keratometry values were recorded.

Results

Among 15,063 cataract surgery candidates (15,063 eyes), 1,921 patients (12.8%, 1,921 eyes) in the high myopia group and 11,880 patients (11,880 eyes) in the control group were enrolled. In the high myopia group, the mean age was 59.8±12.6 (standard deviation) years, which was younger than that in the control group (69.1±11.0 years, P<0.001). In the high myopia group, the mean corneal astigmatism was 1.20±0.83 dioptre (D), which was greater than that in the control group (0.93±0.69 D, P<0.001). In the high myopia group, 82.2% had corneal astigmatism ≥0.50 D, 51.4% ≥1.00 D, 27.4% ≥1.50 D and 14.4% ≥2.00 D, all of which were higher than the respective proportions in the control group (P<0.001 for all). In the high myopia group, 66.8% had moderate to high corneal astigmatism, and 42.8% had “with-the-rule” astigmatism, and both of these proportions were higher than the respective proportions in the control group (P<0.001 for both). In the high myopia group, corneal astigmatism tended to increase with increasing age (r =0.134, P<0.001) after the age of 50, which was consistent with the tendency in the control group.

Conclusions

A significant burden of preoperative corneal astigmatism was observed in Chinese cataract surgery candidates with high myopia. Moderate to high corneal astigmatism was more common in highly myopic eyes than in normal AL eyes.

Two-year outcomes after full-thickness astigmatic keratotomy combined with small-incision lenticule extraction for high astigmatism

Background

To evaluate clinical outcomes after full-thickness astigmatic keratotomy (FTAK) combined with small-incision lenticule extraction (SMILE) in eyes with high astigmatism.

Methods

This study comprised 75 eyes of 43 patients with over 4.0 diopters (D) of astigmatism who were treated with SMILE after FTAK. Visual acuities and refractive measurements were evaluated at 1 month after FTAK, and 1, 6, 12, and 24 months after SMILE. Vector analysis of the astigmatic changes was performed using the Alpins method.

Results

Twenty-four months after the combined procedure, the average spherical equivalent was reduced from − 6.56 ± 2.38 D to − 0.36 ± 0.42 D (p < 0.001). The uncorrected and corrected distance visual acuities improved from 1.54 ± 5.53 to − 0.02 ± 0.09 and from − 0.03 ± 0.07 D to − 0.07 ± 0.08 D (both p < 0.001), respectively. The preoperative mean astigmatism was − 5.48 ± 1.17 D, which was reduced to − 2.27 ± 0.97 D and − 0.34 ± 0.26 D at 1 month after FTAK and 24 months after SMILE, respectively (p < 0.001). The surgically-induced astigmatism after FTAK, SMILE, and FTAK and SMILE combined was 3.38 ± 1.18 D, 2.22 ± 0.84 D, and 5.39 ± 1.20 D, respectively. Furthermore, the correction index of FTAK, SMILE, and FTAK and SMILE combined was 0.63 ± 0.17, 0.90 ± 0.40, and 0.98 ± 0.06, respectively. There were no intraoperative or postoperative complications.

Conclusion

Our surgical procedure combining FTAK and SMILE showed good and stable clinical outcomes during two-year follow-up for the treatment of high astigmatism.

Refractive outcomes of high-magnitude astigmatism correction using femtosecond LASIK versus transepithelial PRK

PURPOSE

To compare the outcomes of femtosecond laser assisted in situ keratomileusis (FS-LASIK) with transepithelial photorefractive keratectomy (T-PRK) for the correction of high-grade astigmatism.

METHODS

Medical records of patients with astigmatism of 2 diopters (D) or higher, who were treated with FS-LASIK or T-PRK in 2013 through 2014 at a private practice laser clinic, were retrospectively analyzed. Efficacy, safety, predictability and vector analysis of astigmatism correction were compared between the treatment groups.

RESULTS

The study included 93 eyes treated with FS-LASIK and 186 eyes treated with T-PRK. No significant differences in postoperative spherical equivalent (-0.10 ± 0.7 D and -0.11 ± 0.7 D, respectively, p = 0.958) and postoperative refractive astigmatism (0.79 ± 0.54 D and 0.82 ± 0.63 D, respectively, p = 0.685) were demonstrated. A significant advantage of FS-LASIK over T-PRK was seen for the efficacy (1.00 ± 0.18 and 0.86 ± 0.22, respectively, p < 0.001) and safety (1.03 ± 0.17 and 0.89 ± 0.21, respectively, p < 0.001) indices. Results remain statistically significant in a multivariate analysis model. Vector analysis for the astigmatism correction showed no significant difference between the surgery methods in the surgically induced astigmatism, difference vector, correction index and index of success.

CONCLUSION

Both procedures demonstrated desirable post-operative SE outcomes for high-grade astigmatism correction. However, FS-LASIK achieved better results than T-PRK in the efficacy and safety parameters.

Initial Single-Site Experience Using SMILE for the Treatment of Astigmatism in Myopic Eyes and Comparison of Astigmatic Outcomes with Existing Literature

Purpose

To assess a single site’s initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes and vector analysis results with the US Food and Drug Administration (FDA) results and published literature.

Patients and Methods

Forty-eight eyes (29 patients) with mean preoperative sphere of −5.11 ± 1.31 diopters (D) and cylinder of −1.12 ± 0.60 D underwent SMILE. Visual acuity, refractive, and vector analysis outcomes as well as subjective measures were reported at three and twelve months postoperatively and compared with FDA results and the published literature between 2014 and 2020 involving treatment of patients with mean cylinders of >−0.50 to ≤−3.00 D.

Results

At three and twelve months, 43 and 32 eyes were evaluated, respectively. At twelve months, mean cylinder power was reduced to −0.38 ± 0.38 D with 78.1% achieving ≤±0.50 D. Uncorrected distance visual acuity (UDVA) ≥20/20 was achieved in 77.4% of eyes by twelve months with 100% achieving ≥20/30 UDVA. No loss of corrected distance visual acuity was observed in eyes seen at twelve months. Correction index (CI) at twelve months was 0.90 indicating overall undercorrection of 10%. Twelve-month CI was 0.96, 0.90, and 0.83 in eyes with preoperative cylinders of <−1.00 D, ≥−1.00 to <−2.00 D, and ≥−2.00 D, respectively. Mean angle of error was −1.58 ± 11.61° ranging from −24.22° to 37.75°.

Conclusion

We found SMILE to be an effective and safe means of achieving spectacle independence and improving visual acuity in patients with myopic astigmatism. SMILE has the potential for improved clinical outcomes with better nomogram guidance and advancements in technique. However, surgeons must be aware of the potential for undercorrection in with-the-rule astigmatism and at higher preoperative cylinders and as well as the potential for overcorrection in against-the-rule and lower preoperative cylinder astigmatism.

Comparison between aberration-free transepithelial photorefractive keratectomy and small incision lenticule extraction for correction of myopia and myopic astigmatism

PURPOSE

To evaluate the clinical outcomes of small incision lenticule extraction (SMILE) and aberration-free transepithelial photorefractive keratectomy (AF t-PRK) in patients with low to moderate myopic astigmatism, including visual acuity, refractive outcomes, astigmatic vector analysis and corneal aberrometric changes.

METHOD

This retrospective comparative case series study involved 110 right eyes of 110 patients who underwent either SMILE (55 eyes) or AF t-PRK (55 eyes). Visual acuity, manifest refractive error and corneal higher-order aberrations (HOAs) were measured and analyzed at baseline, 1 month and 3 months after operation. The safety and efficacy indices, and vector parameters were also compared.

RESULT

1 month postoperatively, the mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) and spherical equivalent refraction (SE) were better after SMILE than AF t-PRK (logMAR UDVA,  - 0.03 ± 0.07 and  - 0.006 ± 0.07, P = 0.050; logMAR CDVA,  - 0.06 ± 0.07 and  - 0.03 ± 0.07, P = 0.043; SE,  - 0.04 ± 0.25 and 0.15 ± 0.26, P < 0.001). However, these parameters were comparable between the groups at 3 months after surgery. Residual astigmatism ≤ 0.25 diopters was observed in 74.5% and 90.9% (P = 0.023) of the eyes at one month and in 87.3% and 85.5% (P = 0.781) of the eyes at 3 months after SMILE and AF t-PRK, respectively. There were no significant differences between the groups in any of the vector parameters at 1 month or 3 months after surgery. Coma and total HOAs after SMILE were significantly higher than AF t-PRK (1 month coma, 0.49 ± 0.23 and 0.29 ± 0.15, P < 0.001; 1 month total RMS HOAs, 0.65 ± 0.20 and 0.54 ± 0.14, P = 0.001; 3 months coma, 0.50 ± 0.22 and 0.30 ± 0.17, P < 0.001; 3 months total RMS HOAs, 0.68 ± 0.20 and 0.55 ± 0.17, P < 0.001).

CONCLUSION

In this study, both SMILE and AF t-PRK were effective and comparable for correction of low to moderate myopic astigmatism. AF t-PRK group induced less coma and total HOAs than SMILE.

Long-term Vector Outcomes of SMILE in Correcting Moderate to High With-the-Rule Astigmatism Under Astigmatism Axis Marked Condition

PURPOSE

To evaluate the vector outcomes of small incision lenticule extraction (SMILE) in correcting moderate to high myopic astigmatism under astigmatic axis marked condition.

METHODS

In a prospective, longitudinal, interventional study, 71 eyes (71 patients) that had with-the-rule preoperative cylinder refraction exceeding 1.50 diopters (D) were corrected with the VisuMax femtosecond laser (Carl Zeiss Meditec AG) at Zhongshan Ophthalmic Center. Refractive outcomes and astigmatic vector were evaluated preoperatively and at 1, 3, 6, and 30 months postoperatively.

RESULTS

At 30 months postoperatively, the efficacy and safety indexes were 1.04 ± 0.18 and 1.15 ± 0.17, respectively. The magnitude of the surgically induced astigmatism (SIA) (2.13 ± 0.71 D at 1 month [P_1m-pre = .018], 2.12 ± 0.72 D at 3 months [P_3m-pre = .006], 2.13 ± 0.69 D at 6 months [P_6m-pre = .010], and 2.19 ± 0.72 D at 30 months [P_30m-pre < .001]) was slightly higher than that of the target induced astigmatism (TIA) (2.07 ± 0.69 D). Only the y-coordinate of the SIA vector had a significant overcorrection compared to that of the TIA vector (P_1m-pre = .033, P_3m-pre = .011, P_6m-pre = .012, P_30m-pre < .001). The corrected index (CI = |SIA|/|TIA|) varied from 1.03 ± 0.07 at 1 month to 1.06 ± 0.10 at 30 months, which was higher when correcting moderate astigmatism than when correcting high astigmatism (P = .041) at 30 months postoperatively.

CONCLUSIONS

SMILE had long-term safety, efficacy, predictability, and stability when correcting moderate to high myopic astigmatism under astigmatism axis marked condition. Meanwhile, a cylinder overcorrection was observed due to the overcorrection of y-coordinate astigmatic power, which implied that the vector adjustment of the cylinder refraction nomogram should be considered. [J Refract Surg. 2020;36(9):585-591.].

Four-year outcomes of small incision lenticule extraction (SMILE) to correct high myopic astigmatism

AIMS

To evaluate the long-term outcomes of small incision lenticule extraction (SMILE) in subjects with myopic astigmatism of ≥2.00 dioptres (D).

METHODS

Patients who underwent SMILE 4 years prior with astigmatism ≥2.00 D and ≤1.00 D were assigned to the high astigmatic group (HA group) or the low astigmatic group (LA group), respectively. The visual and refractive results as well as corneal wavefront aberrations were measured.

RESULTS

The preoperative cylinder was -2.47±0.54 D in 43 eyes in the HA group and -0.55±0.28 D in 31 eyes in the LA group. At 4 years, the residual cylinder was -0.31±0.29 D in the HA group and -0.20±0.28 D in the LA group (p=0.088). An uncorrected distance visual acuity of 20/20 was achieved in 88.4% of eyes in the HA group and 93.5% of eyes in the LA group. The efficacy index was 0.99±0.14 and 1.10±0.21 (p=0.025), and the safety index was 1.11±0.20 and 1.22±0.21 in the HA and LA groups, respectively (p=0.012). Eighty-six per cent and 90.3% of eyes were within ±0.50 D of the attempted cylindrical correction in the HA and LA groups, respectively. Vector analysis showed that the magnitude of error was -0.14±0.28 D and -0.05±0.16 D (p=0.085), the angle of error was -0.13±4.48 degrees and -2.57±29.42 degrees (p=0.592), the correction index was 0.94±0.13 and 0.94±0.35 (p=0.959), the index of success was 0.15±0.14 and 0.46±0.62 (p=0.517), and the flattening index was 0.93±0.13 and 0.71±0.59 (p=0.450) in the HA and LA groups, respectively.

CONCLUSIONS

This study demonstrates that SMILE is effective and safe for correcting high astigmatism. Vector analysis shows a tendency for the undercorrection of astigmatism in subjects with high astigmatism.

Detection of and Compensation for Static Cyclotorsion With an Image-Guided System in SMILE

PURPOSE

To evaluate the effect of cyclotorsion compensation with an image-guided system (Callisto eye; Carl Zeiss Meditec AG, Jena, Germany) on the visual and refractive outcomes of small incision lenticule extraction (SMILE) surgery for astigmatism.

METHODS

The medical records of 124 right eyes of 124 patients with astigmatism of 0.75 diopters (D) or greater who underwent SMILE for myopic astigmatism were reviewed. Patients were treated with cyclotorsion compensated SMILE or standard SMILE. After the sitting position reference axis was registered with IOLMaster 700 (Carl Zeiss Meditec AG), these data were transferred to the Callisto eye system, which was connected to the operating VisuMax microscope (Carl Zeiss Meditec AG). Cyclotorsion was measured by activating the Z-align function and compensated for by repositioning the patient's body or tilting the head until the reference axis from the IOLMaster 700 (0-180) was parallel to a manually drawn reference axis on the screen (0-180) before docking. The visual and refractive results were studied preoperatively and postoperatively. Astigmatic changes were interpreted using the Alpins method.

RESULTS

Six months after surgery, the results showed that the astigmatic eyes in the cyclotorsion compensated group had improved axial alignment, more precise astigmatic correction, and better postoperative uncorrected distance visual acuity (UDVA) compared with the standard group. The mean logMAR UDVA was 0.02 ± 0.10 (range: -0.15 to 0.30) and 0.06 ± 0.11 (range: -0.15 to 0.30) (P = .13) and the mean astigmatic error was -0.19 ± 0.17 D (range: -0.50 to 0.00 D) and -0.45 ± 0.38 D (range: -1.50 to 0.00 D) (P < .001) in the cyclotorsion compensated group and the standard group, respectively. In regard to vector analysis, the mean index of success was 0.00 ± 0.00 (range: 0.00 to 0.00) and 0.40 ± 0.48 (range: 0.00 to 2.72) (P < .001), and the mean absolute angle of error in degrees was 1.18 ± 2.23 (range: 0.00 to 13.00) and 3.76 ± 3.80 (range: 0.00 to 14.00) (P < .001) in the cyclotorsion compensated group and the standard group, respectively.

CONCLUSIONS

The combination of the Callisto eye system with a VisuMax laser might be an efficacious and reliable approach to enhance astigmatism treatment with SMILE surgery. [J Refract Surg. 2020;36(3):142-149.].

Small-Incision Lenticule Extraction (SMILE) for the Correction of Myopia with Astigmatism: Outcomes of the United States Food and Drug Administration Premarket Approval Clinical Trial

PURPOSE

To present outcomes of the United States Food and Drug Administration premarket approval clinical trial of small-incision lenticule extraction (SMILE) for the correction of myopia and astigmatism.

DESIGN

Prospective, multicenter clinical trial.

PARTICIPANTS

The study included 357 eyes of 357 patients treated with SMILE (50 for myopia and 307 for myopia with astigmatism). Preoperative sphere ranged between -1.00 and -10.00 diopters (D), with manifest spherical equivalent (MSE) of up to -11.50 D and refractive cylinder of up to -3.00 D.

METHODS

-Participants were followed up for 12 months. Corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA), stability of the manifest refraction, and vector analysis of refractive cylinder are presented for the 307 eyes treated for myopia with astigmatism. Adverse events (AEs) are presented for all 357 eyes.

MAIN OUTCOME MEASURES

Corrected distance visual acuity, uncorrected distance visual acuity, manifest refraction, astigmatic outcomes, and adverse events.

RESULTS

Of the 307 astigmatic eyes enrolled in the study, 304 were treated successfully. In 3 eyes, the procedure was aborted because of intraoperative suction loss. The mean MSE reduced from -5.39±2.30 D at baseline to -0.01±0.24 D at 12 months. Of all eyes, 95.3% were within 0.50 D of emmetropia at 12 months. The percentage of eyes with UDVA of 20/20 or better was 89.0%. No loss of 2 or more lines of CDVA was observed at the 12-month visit. The refractive cylinder reduced from -1.53±0.70 D at baseline to -0.18±0.31 D at 12 months. The mean correction ratio of refractive cylinder was 0.96±0.16 and a slight undercorrection was apparent for higher attempted corrections of astigmatism. Three intraoperative AEs associated with difficult lenticule removal and resultant cap tear occurred, and all resolved without sequelae at postoperative day 1. During the postoperative period, 8 AEs were recorded, but none of them had significant consequences.

CONCLUSIONS

Small-incision lenticule extraction for the treatment of myopia and astigmatism was safe and effective, and the reported AEs had no significant impact on visual acuity. Slight undercorrection of refractive cylinder requires further attention.

Review on Centration, Astigmatic Axis Alignment, Pupil Size and Optical Zone in SMILE

The advent of "flapless" small-incision lenticule extraction (SMILE), employing all-in-one technology, has resulted in a revolutionary breakthrough in refractive surgeries. SMILE has been gaining popularity due to fewer potential complications, such as postoperative dry eyes and greater biomechanical stability, etc. However, attention must be given to 1) the centration on the corneal vertex, 2) the proper alignment of the astigmatic axis, and 3) the relationship between pupil size and treatment diameter, to achieve good SMILE results. There is no pupil-tracking system to ascertain the accuracy of centration during the SMILE surgery. To improve the centration accuracy, our center uses two corneal topographers (Pentacam and Sirius) to measure and determine corneal vertex. Proper predicted optical zone diameter is not clearly defined yet in SMILE. Some scholars insist that mesopic pupil size should be taken into consideration when setting the predicted optical zone. Meanwhile, the issue of "functional optical zone" still has many unresolved issues and warrants further studies.

Astigmatism Correction Using SMILE

Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.

Clinical outcomes of mechanical and transepithelial photorefractive keratectomy in low myopia with a large ablation zone

PURPOSE

To evaluate the clinical outcomes, vector parameters, and aberrations between mechanical photorefractive keratectomy (PRK) and transepithelial PRK in eyes with low myopia.

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, Korea.

DESIGN

Retrospective, comparative case series.

METHODS

Eighty-four eyes of 84 patients with low myopia (≤2.00 diopters) were treated with mechanical or transepithelial PRK (41 eyes and 43 eyes, respectively), with the application of a large optical zone (OZ). Visual acuity, manifest refraction, slitlamp evaluation, autokeratometry, corneal topography, and the evaluation of corneal wavefront aberrations were measured preoperatively and at 1, 3, and 6 months after surgery. The efficacy, predictability, vector parameters, corneal aberrations, and safety at 6 months after surgery were compared between the two treatment groups.

RESULTS

The mean uncorrected distance visual acuity was comparable, at -0.13 ± 0.05 (SD) and -0.15 ± 0.05, in the mechanical and transepithelial PRK groups, respectively, at 6 months after surgery. The safety and efficacy indices, vector parameters, and aberrometric values were also comparable between the two groups. The OZ was large in both groups (7.09 ± 0.20 mm and 7.12 ± 0.27 mm in the mechanical PRK and transepithelial PRK groups, respectively), and showed no significant difference between groups. The corneal total root-mean-square higher-order aberrations and coma significantly reduced after treatment in both groups, and spherical aberrations significantly decreased after transepithelial PRK.

CONCLUSIONS

Mechanical and transepithelial PRK with a large OZ provided effective and safe outcomes for the correction of low myopia without differences in visual acuity and refractive outcomes between procedures.

Comparing corneal higher-order aberrations in corneal wavefront-guided transepithelial photorefractive keratectomy versus small-incision lenticule extraction

PURPOSE

To evaluate the changes in corneal higher-order aberrations (HOAs) after corneal wavefront-guided transepithelial photorefractive keratectomy (PRK) and small-incision lenticule extraction (SMILE).

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, South Korea.

DESIGN

Retrospective case series.

METHODS

Medical records of patients having either corneal wavefront-guided transepithelial PRK or small-incision lenticule extraction were examined. The root-mean-square total HOAs, 3rd-order coma aberration, and 4th-order spherical aberration were measured preoperatively and 6 months postoperatively. Independent t tests and analysis of covariance were used to compare changes in corneal HOAs between the 2 groups.

RESULTS

The study comprised 77 eyes having corneal wavefront-guided transepithelial PRK and 81 eyes having small-incision lenticule extraction. The total HOAs and spherical aberration increased after transepithelial PRK (all P < .001), whereas coma aberration was stable after transepithelial PRK. The total HOAs, spherical aberration, and coma aberration increased after small-incision lenticule extraction (P < .001 for total HOAs, spherical aberration; P = .004 for coma). At 6 months postoperatively, total HOAs and spherical aberration were significantly larger in the transepithelial PRK group than in the small-incision lenticule extraction group. Coma aberration was larger in the small-incision lenticule extraction group than in the transepithelial PRK group. Spherical aberration induction was significantly smaller in the small-incision lenticule extraction group than in the transepithelial PRK group (P < .001), and coma aberration induction was larger in the small-incision lenticule extraction group than in the transepithelial PRK group (P = .011).

CONCLUSIONS

Small-incision lenticule extraction demonstrated that the induction of total HOAs was comparable to corneal wavefront-guided transepithelial PRK, accompanied by smaller spherical aberration induction and larger coma aberration induction. During small-incision lenticule extraction, surgeons should aim to obtain optimum centration for smaller induction of corneal HOAs.