Development of the continuous curvilinear lenticulerrhexis technique for small incision lenticule extraction

Refractive Corneal Lenticule Extraction With the CLEAR Femtosecond Laser Application

PURPOSE

The aim of this study was to evaluate a new femtosecond laser application for refractive corneal lenticule extraction with suction control and computerized regulation of centration and alignment (Ziemer CLEAR).

METHODS

This was a retrospective, consecutive, noncomparative case series study. Patients undergoing CLEAR for spherical equivalent (SE) between -3 and -10 D, evaluating SE, defocus equivalent, refractive astigmatism, visual acuity, and centration at 10 months were evaluated in the study.

RESULTS

Fifty-three eyes of 42 patients (mean age 40.4 ± 8.6 years) were included, with preoperative SE -5.99 ± 1.49 D and mean corrected distance visual acuity (CDVA) of 0.05 ± 0.07 logMAR. With no suction losses, an intact lenticule was extracted in all eyes. In 6 eyes, peripheral adhesion was resolved by lenticulerrhexis, and in 1 eye, the incision was opened by a crescent blade. Moderate interface inflammation occurred in 3 eyes. At day 1, in the 42 eyes with uneventful surgery, the mean CDVA was 20/27, whereas in the 11 eyes with extra surgical manipulations, it was 20/36 ( P = 0.04). At 10 months, for the 53 eyes, the mean uncorrected distance visual acuity was 0.05 ± 0.09 logMAR; in 37 eyes (70%), it was 20/25 or better; and the mean CDVA was 0.04 ± 0.06 logMAR. Eight eyes (15%) lost 1 logMAR line. The mean SE was -0.13 ± 0.15 D. The mean defocus equivalent was 0.33 ± 0.32 D, with 46 eyes (87%) ≤0.50 D and 52 eyes (98%) ≤1 D. Refractive astigmatism was ≤0.50 D in 48 eyes (90%). The efficacy index was 1.00, and the safety index was 0.98. The mean decentration from the corneal vertex was 0.28 ± 0.07 mm.

CONCLUSIONS

The application yielded good predictability, efficacy, and safety. Slower visual recovery was observed after extra surgical manipulations.

Modified Technique for Small-Incision Lenticule Extraction: Ye's Swing Technique

INTRODUCTION

This study aimed to evaluate the lenticule integrity and refractive outcomes of a new technique, Ye's swing technique, during small-incision lenticule extraction (SMILE).

METHODS

This prospective study enrolled patients who underwent the SMILE procedure using a modified technique for lenticule dissection. Per the standard SMILE procedure, the cap cut was opened using a hook, and an anterior dissection was performed with a counterclockwise swing, from 8 to 12 o'clock. A posterior dissection was then performed by swinging counterclockwise, leaving a thin band of the peripheral rim undissected, from 8 to 4 o'clock. The counterclockwise swing was continued to separate the edges of the rim from 4 to 12 o'clock, after which microforceps were used to extract the lenticules. The primary outcome measures were safety and lenticule integrity at the end of the surgery, and the secondary outcome measure was efficacy. Changes in the ocular parameters from the preoperative visit to 1 month postoperative, including uncorrected and corrected distance visual acuity, manifest refraction, lenticule quality, and lenticule residual, were assessed using optical coherence tomography.

RESULTS

A total of 246 patients (490 eyes) with myopia and myopic astigmatism were included in the present study. The dissected lenticules ranged in size from 52 to 148 µm. Postoperatively, the lenticule was completely and successfully extracted in all cases. There was no incisional edge tearing during lenticule separation.

CONCLUSIONS

Ye's swing technique is a safe and effective procedure for lenticule dissection and refractive outcomes. We have now adopted this technique as our routine method for performing the SMILE procedure.

Five-year stability of posterior corneal surface after small incision lenticule extraction for high myopia

Background

To study the 5-year changes in the posterior corneal surface after small incision lenticule extraction (SMILE) for high myopia.

Methods

Eighty eyes received SMILE was included in this prospective study. They were allocated into two groups based on the spherical equivalent: high myopia (40eyes, -7.49 ± 0.70D) and moderate myopia (40eyes, -4.43 ± 0.87D). Certain points of posterior corneal elevation (the central point (PCE), thinnest point (PTE), maximal point (PME), and in various corneal areas) were evaluated using a Scheimpflug camera (Pentacam; Oculus GmbH, Germany) preoperatively and at 6 months and 5 years after surgery.

Results

All surgeries were completed uneventfully and no ectasia was developed throng the observation. The safety index and efficacy index were 1.14 and 1.03 in the high myopia group, and 1.16 and 1.06 in the moderate myopia group, respectively. Most of the calculated values in the high myopia group showed a slight increase at 6 months but decreased at 5 years. At 5 years postoperatively, the value of the PTE was significantly lower than at baseline in both groups (P ≤ 0.047); a statistical difference was also revealed in the PME in the moderate group with slight changes (10.15 ± 3.01 μm vs. 11.60 ± 4.33 μm, P = 0.002); no statistical significance was observed in other calculated values (P ≥ 0.067). Similarly, no significant linear correlation was noted between changes in all values and the residual bed thickness either (P ≥ 0.057).

Conclusions

SMILE causes no protrusion in posterior corneal surface for correction of high myopia at the follow-up visit of 5 years.

Bilateral Lenticule Creation Followed by Bilateral Lenticule Separation Improves Visual Outcomes After SMILE

PURPOSE

To explore the impact of different surgical sequences on the visual and refractive outcomes of bilateral small incision lenticule extraction (SMILE) surgery using propensity score matching (PSM) analysis.

METHODS

Participants who underwent uneventful SMILE between March 2018 and September 2019 were retrospectively analyzed and were divided into two groups: Sequence A (laser scanning [LS] of the right eye, manual separation lenticule [MSL] of the right eye, and LS and MSL of the left eye) and Sequence B (LS of the right eye, LS of the left eye, MSL of the left eye, and MSL of the right eye). PSM was conducted to minimize the effect of confounding factors on postoperative visual outcomes at days 1 and 7 and months 1, 3, and 6. Safety, efficacy, predictability, and stability were compared between groups.

RESULTS

Overall, 1,854 eyes of 927 participants were included (Sequence A, n = 280; Sequence B, n = 647). After PSM, there were no significant differences in baseline characteristics, and 534 eyes (267 patients) in the Sequence A group were matched (1:1) to the Sequence B group. The postoperative corrected distance visual acuity significantly differed between groups at 3 months (adjusted P = .007). The uncorrected distance visual acuity significantly differed between groups at all follow-up visits (adjusted P < .01). The safety index (1.341 ± 0.265 and 1.413 ± 0.294) and efficacy index (1.173 ± 0.191 and 1.251 ± 0.269) were different in the Sequence A and Sequence B groups, respectively, at 3 months (adjusted P < .01). No difference in visual outcomes was found between right and left eyes.

CONCLUSIONS

Patients who had bilateral lenticule creation followed by bilateral lenticule separation had better postoperative visual outcomes than those who underwent complete SMILE surgery in each eye separately. Regardless of the surgical sequence chosen for the SMILE procedure, there was no impact on outcomes between the right and left eyes. Adjusting the sequence of the surgical procedure may be a way to improve the visual results. [J Refract Surg. 2021;37(11):726-733.].

Corneal lenticule extraction assisted by a low-energy femtosecond laser

A lenticule of intrastromal corneal tissue was cut together with 2 small incisions of 3.0 mm using a low-energy femtosecond laser system, FEMTO LDV Z8; 1 incision led to the posterior plane and 1 to the anterior, allowing dissection of the lenticule. When needed, recentering of the treatment area was possible without repeating the docking stage. Five eyes were operated, and a complete dissection and removal of the lenticule was achieved in all cases without any intraoperative complications. In addition, at postoperative day 1, all patients had a clear cornea. In conclusion, guided lenticule extraction using a low-energy femtosecond laser was a promising and easy procedure.

Inverse centripetal dissection: A rescue technique for mis-dissected lenticule during SMILE

Management of mis-dissected lenticule during Small-incision lenticule extraction (SMILE) is technically challenging and might be experienced more by novice surgeons especially in eyes with low refractive errors and thin lenticules. Presently, we describe a rescue method of inverse centripetal dissection (ICD) to manage mis-dissected lenticules. In this technique, after inadvertent dissection of posterior plane prior to anterior plane, the double-ended SMILE dissector is rotated along its shaft axis clockwise from the left upper margin of the mis-dissected lenticule to form an inversely folded lenticule which is then subsequently dissected centripetally till midline. This is then extracted by performing lenticulorrhexis with a pair of microforceps. We performed this technique in 10 eyes of 10 patients and the lenticule extraction was accomplished successfully in all eyes. At six months follow-up, the uncorrected visual acuity was 20/20 with a clear interface in all eyes. The ICD approach might serve as a useful rescue technique for managing mis-dissected lenticules.

Stop sign for correct tissue plane identification in small incision lenticule extraction

We describe the “stop sign“ which allows correct anterior and posterior lenticular plane delineation in Small Incision Lenticule Extraction (SMILE). This sign describes the resistance noted at the junction between the dissected and undissected halves of both the planes, interfering with subsequent lateral movement of the instrument. The resistance is demonstrated at both the anterior and posterior lenticular plane. This allows ideal dissection of the lenticule from the overlying cap and underlying stroma, thereby reducing the complications arising from incorrect tissue dissection.

Advances in refractive corneal lenticule extraction

Refractive errors are the leading cause of reversible visual impairment worldwide. In addition to the desired spectacle independence, refractive procedures can improve quality of life, working ability, and daily working performance. Refractive corneal lenticule extraction (RCLE) is a relatively new technique, dependent only on a femtosecond laser (FS). This leads to potential benefits over laser-assisted in situ keratomileusis (LASIK) including a quicker recovery of dry eye disease, a larger functional optical zone, and no flap-related complications. SMILE, available with the VisuMax FS (Carl Zeiss Meditec AG, Jena, Germany), is the most established RCLE application, offering visual and refractive outcomes comparable to LASIK. SmartSight (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany) and CLEAR (Ziemer Ophthalmic Systems AG, Port, Switzerland) are two new RCLE applications that received Conformité Européenne (CE) approval in 2020. In this article, we review refractive and visual outcomes, advantages, and disadvantages of RCLE and also report on the latest advances in RCLE systems.

The comparison of visual outcomes, aberrations, and Bowman's layer micro-distortions after femtosecond laser small-incision lenticule extraction (SMILE) for the correction of high and moderate myopia and myopic astigmatism

Background

This study compares the clinical outcomes of femtosecond laser small-incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism greater than − 10 D, and − 10 D or less respectively.

Methods

60 eyes/patients were equally selected into group 1 (myopia and myopic astigmatism of − 10 D or less) and group 2 (myopia and myopic astigmatism of over − 10 D), both of which were treated with SMILE. Visual and refractive outcomes, corneal higher-order aberrations, and Bowman’s layer micro-distortions were evaluated preoperatively, 3 months, and 6 months postoperatively.

Results

LogMAR corrected distance visual acuity (CDVA) of group 1 and group 2 was − 0.069 ± 0.047 and − 0.053 ± 0.073 6 months postoperatively (P = 0.48). 100% eyes in group 1 and 97% in group 2 were within 1 D of targeted correction (P = 0.45). Meanwhile, 100% eyes in group 1 and 97% in group 2 had an uncorrected distance visual acuity of 20/25 or better (P = 0.20). Changes in corneal higher-order aberrations root mean square, coma, and trefoil were similar between the two groups but spherical aberration was higher in group 2 (P < 0.01). Micro-distortions were observed in 53% in group 1 and 77% in group 2. More micro-distortions were observed in group 2 (3.40 ± 2.66) than in group 1 (2.07 ± 2.29) (P = 0.041). The total number of micro-distortions was not correlated with postoperative CDVA (P = 0.77).

Conclusions

Visual outcomes showed similar results of SMILE for myopic correction of > − 10 D and ≤ − 10 D. Refractive outcomes showed slightly under-correction in higher myopic eyes. Higher myopic treatment tends to induce more spherical aberrations. Micro-distortions had no impact in visual and refractive outcomes.

Small incision lenticule extraction (SMILE) techniques: patient selection and perspectives

Refractive lenticule extraction is becoming the procedure of choice for the management of myopia and myopic astigmatism owing to its precision, biomechanical stability, and better ocular surface. It has similar safety, efficacy, and predictability as femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and is associated with better patient satisfaction. The conventional technique of small incision lenticule extraction (SMILE) involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and extraction. It has a steep learning curve compared to conventional flap-based corneal ablative procedures, and the surgical technique may be challenging especially for a novice surgeon. As SMILE is gaining worldwide acceptance among refractive surgeons, different modifications of the surgical technique have been described to ease the process of lenticule extraction and minimize complications. Good patient selection is essential to ensure optimal patient satisfaction, and novice surgeons should avoid cases with low myopia (thin refractive lenticules), difficult orbital anatomy, high astigmatism, or uncooperative, anxious patients to minimize complications. A comprehensive MEDLINE search was performed using “small incision lenticule extraction,” “SMILE,” and “refractive lenticule extraction” as keywords, and we herein review the patient selection for SMILE and various surgical techniques of SMILE with their pros and cons. With increasing surgeon experience, a standard technique is expected to evolve that may be performed in all types of cases with optimal outcomes and minimal adverse effects.

Development of a liquid dissection technique for small-incision lenticule extraction: Clinical results and ultrastructural evaluation

PURPOSE

To determine the effect of a liquid dissection technique on clinical outcomes with ultrastructural analysis of the lenticule surface in small-incision lenticule extraction (SMILE).

SETTING

Zhongshan Ophthalmic Center, Guangzhou, China.

DESIGN

Prospective case series.

METHODS

Consecutive patients with myopia scheduled for small-incision lenticule extraction were included. The liquid dissection technique was performed in 1 eye and the traditional dissection technique was performed in the other eye by randomized assignment. Ophthalmic examinations were evaluated preoperatively and at different timepoint follow-ups after small-incision lenticule extraction. Ten human corneal lenticules were analyzed using scanning electron microscopy.

RESULTS

The study comprised 29 patients (58 eyes). Uncorrected distance visual acuity (logarithm of the minimum angle of resolution) postoperative measurements at 2 and 4 hours were significantly better in the liquid dissection group than in the traditional dissection group (P < .001 and P = .001, respectively); however, there were no significant differences between the 2 groups at 1 day, 1 week, and 1 month postoperatively. Compared with the traditional dissection technique, the liquid dissection technique induced significantly fewer corneal aberrations at 2 hours and 1 month after the procedures (P = .031 and P = .016, respectively), the postoperative contrast sensitivity in the liquid dissection group was significantly higher after 1 day (P = .01). The liquid dissection samples showed smoother lenticule surfaces compared with the traditional dissection samples qualitatively and quantitatively (P = .004 and P < .001, respectively).

CONCLUSION

The liquid dissection technique was helpful in facilitating better visual acuity recovery and produced smooth cuts in the early postoperative period.

Short-term Observation of Intraocular Scattering and Bowman's Layer Microdistortions After SMILE-CCL

PURPOSE

To investigate changes in intraocular scattering and Bowman's layer microdistortions after femtosecond laser small incision lenticule extraction using the continuous curvilinear lenticulerhexis technique (SMILE-CCL).

METHODS

In this prospective study, 93 eyes of 93 patients (44 women, 49 men) were treated with SMILE-CCL. Mean age was 26.09 ± 4.39 years and mean spherical equivalent was -6.31 ± 2.16 diopters. The Objective Scatter Index (OSI) was examined with an objective optical quality analysis system. Bowman's layer microdistortions in the central 4-mm optical zone were measured using Fourier-domain optical coherence tomography.

RESULTS

The mean OSI value increased from 0.67 preoperatively to 1.09 at 20 days, and then decreased to 0.84 at 3 months (P < .05). Microdistortions were observed in 62.37% of the eyes at 20 days and 48.39% at 3 months postoperatively (P < .05). The width of the microdistortions per meridian was 283.18 ± 197.19 μm at 20 days; this decreased to 156.00 ± 159.86 μm at 3 months (P < 0.05). Regression analysis models revealed that older age (b = 0.02, P = .03) and higher preoperative spherical equivalent (b = -0.09, P < .05) resulted in higher postoperative OSI values; no significant association was found between postoperative OSI values and microdistortion-related parameters (P > .05). Higher preoperative spherical equivalent (b = -0.28, P = .01) and thinner preoperative corneal thickness (b = -0.02, P = .01) were associated with more microdistortions.

CONCLUSIONS

SMILE induced a temporary increase in OSI values and Bowman's layer microdistortions. The microdistortions did not influence intraocular scattering. [J Refract Surg. 2018;34(6):387-392.].

Intraoperative Optical Coherence Tomography-Guided Management of Cap-Lenticule Adhesion During SMILE

PURPOSE

To report successful lenticule extraction using intraoperative optical coherence tomography (OCT) in a case of cap-lenticule adhesion during small incision lenticule extraction (SMILE).

METHODS

Case report.

RESULTS

A 22-year-old patient with a refractive error of -5.00 -0.50 × 120° and -5.00 -0.75 × 60° in the right and left eyes, respectively, was scheduled for SMILE. The lenticule was created using the VisuMax femtosecond laser system (Carl Zeiss Meditec, Jena, Germany). The surgeon experienced difficulty while extracting the lenticule in the right eye. The patient was immediately shifted under the surgical microscope integrated with intraoperative OCT. The lenticule was found to be adherent to the anterior stromal cap, which was seen as hyperreflective spikes in the posterior plane, in contrast to the anterior plane, which showed minimal reflectivity, suggesting an inadvertent posterior plane entry. The peripheral edge of the lenticule was lifted from the anterior stromal cap under direct visualization of intraoperative feedback images provided by intraoperative OCT. The edge of the lenticule, which was freed, was then grasped with microforceps and extracted in toto using the continuous curvilinear lenticulerrhexis technique. At the end of surgery, the intrastromal pocket was screened under intraoperative OCT for any lenticule remnants. One week after surgery, the uncorrected distance visual acuity was 20/20 with smooth, regular interface on anterior segment optical coherence tomography.

CONCLUSIONS

Intraoperative OCT is useful in cases of difficult lenticule extraction during SMILE because it provides real-time visualization of the lenticule and helps in discerning its relation with the anterior stromal cap and the underlying stromal bed. By using intraoperative OCT and the continuous curvilinear lenticulerrhexis technique, satisfactory anatomical and visual outcomes were obtained. [J Refract Surg. 2017;33(11):783-786.].

Early visual outcomes and optical quality after femtosecond laser small-incision lenticule extraction for myopia and myopic astigmatism correction of over -10 dioptres

PURPOSE

To investigate early visual and refractive outcomes, corneal stability and optical quality after femtosecond laser small-incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism over -10 D.

METHODS

Thirty eyes (30 patients) with myopia and myopic astigmatism of over -10 D were treated with VisuMax^® femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany). Six months postoperative safety, efficacy and predictability were evaluated. Corneal Scheimpflug topography was measured preoperatively, 1 day, 3 months and 6 months postoperatively. Wavefront aberrations were measured preoperatively, 3 months and 6 months postoperatively.

RESULTS

Six months postoperatively, LogMAR uncorrected and corrected distance visual acuity (CDVA) were -0.013 ± 0.086 and -0.073 ± 0.069, respectively. 73% (97%) of eyes were within 0.5 (1) D of target refraction. No eyes lost CDVA, 43% (13 eyes) gained one line and 7% (two eyes) gained two lines. Mean corneal back curvature (KMB) and posterior central elevation (PCE) did not change significantly comparing preoperative and 6 months postoperative data (p = 0.91 and 0.77, respectively). Comparing 1 day with 6 months postoperative data, central corneal thickness (CCT), mean corneal front curvature (KMF), KMB and PCE did not change significantly (p = 0.27, 0.07, 0.52, 0.71, respectively). Total higher-order aberration (HOA), spherical aberration and coma increased significantly (p < 0.01) but trefoil remained stable (p = 0.49).

CONCLUSION

Our results indicate that SMILE can correct myopia and myopic astigmatism of over -10 D predictably. No early ectasia was observed. Long-term changes in visual quality and corneal stability require further investigation.

Lenticuloschisis: A "No Dissection" Technique for Lenticule Extraction in Small Incision Lenticule Extraction

PURPOSE

To describe a "no dissection" technique of lenticule removal in small incision lenticule extraction (SMILE).

METHODS

After docking and laser delivery, a microforceps is used to grasp and gently peel off the lenticule from the underlying stromal bed, without performing any dissection of the upper and lower planes of the lenticule. Prerequisites are a surgeon experienced in the conventional SMILE technique, optimized laser energy settings, and a minimum peripheral lenticule thickness of 25 to 30 µm.

RESULTS

The interface as assessed in postoperative dilated clinical photographs was seen to be clearer with less roughness compared to the conventional dissection technique. This may potentially result in better first postoperative visual acuity and quality of vision due to less corneal tissue trauma and minimal tissue handling, thus potentially resulting in faster visual recovery.

CONCLUSIONS

No dissection lenticule removal is a feasible and reproducible technique that may result in better immediate visual quality compared to the conventional SMILE technique. [J Refract Surg. 2017;33(8):563-566.].

Three-Year Stability of Posterior Corneal Elevation After Small Incision Lenticule Extraction (SMILE) for Moderate and High Myopia

PURPOSE

To investigate long-term changes in posterior corneal elevation after small incision lenticule extraction (SMILE).

METHODS

Thirty-six eyes of 20 patients (7 male, 13 female) who underwent SMILE were recruited for this prospective consecutive study. The mean preoperative manifest spherical equivalent was -6.24 ± 1.47 diopters (D) (range: -3.88 to -8.75 D). Posterior corneal surfaces were measured by a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and at 1 month, 6 months, 12 months, 2 years, and 3 years after surgery. Posterior central elevation (PCE), posterior maximal elevation (PME), and posterior elevation at the thinnest corneal point (PTE) in the central 4-mm area above the best-fit sphere (BFS) were analyzed. The BFS was the same across all follow-up periods and determined by the preoperative data. A P value of less than .05 was considered statistically significant.

RESULTS

All surgeries were executed without complications and no case of keratectasia was observed during the follow-up. An uncorrected distance visual acuity of 20/20 or better was achieved in 100% of eyes at the last visit. The mean change of PCE, PME, and PTE at 3 years after the operation was -2.39 ± 2.85, 0.50 ± 3.33, and -2.33 ± 2.90 µm, respectively. There were significant differences in the measurements of PCE and PTE before surgery and 3 years after surgery (P ≤ .009); however, there was no significant difference in PME before surgery and 3 years after surgery (P = 1.000). No correlation was found between changes in posterior corneal elevation and residual bed thickness, ablation depth, and preoperative thinnest corneal thickness.

CONCLUSIONS

The posterior corneal surface, measured using the Pentacam, was stable after SMILE in the long-term follow-up. The cause of the slight backward change of PCE and PTE needs further study. [J Refract Surg. 2017;33(2):84-88.].

Quantitative Evaluation of Microdistortions in Bowman's Layer and Corneal Deformation after Small Incision Lenticule Extraction

Purpose

To quantitatively evaluate microdistortions in Bowman's layer and change in corneal stiffness after small incision lenticule extraction (SMILE).

Methods

This was a prospective, longitudinal, and interventional study. Thirty eyes of 30 patients were screened preoperatively and underwent SMILE for treatment of myopia with astigmatism. Visual acuity, refraction, optical coherence tomography (OCT; Bioptigen, Inc., Morrisville, NC) imaging of the layer and air-puff applanation (Corvis-ST, OCULUS Optikgeräte Gmbh, Germany) was performed before and after surgery (1 day, 1 week, and 1 month). The Bowman's Roughness Index (BRI) was defined as the enclosed area between the actual and an ideal smooth layer to quantify the microdistortions. A viscoelastic model was used to quantify the change in corneal stiffness using applanation.

Results

Uncorrected distance visual acuity improved (P < 0.001) and refractive error decreased (P < 0.0001) after SMILE. BRI increased from preoperative levels (1.81 × 10⁻³ mm²) to 1 week (3.14 × 10⁻³ mm²) after SMILE (P < 0.05) and then decreased up to a month (2.43 × 10⁻³ mm²; P < 0.05). Increase in the magnitude of the index correlated positively with refractive error (P = 0.02). However, corneal stiffness reduced after SMILE (105.86 ± 1.4 N/m versus 97.97 ± 1.21 N/m at 1 month, P = 0.001). The decrease in corneal stiffness did not correlate with refractive error (P = 0.61).

Conclusions

BRI correlated positively the magnitude of refractive error. However, decrease in corneal stiffness, assessed by air-puff applanation, may not be related to microdistortions after SMILE.

Translational Relevance

An objective method of quantification of Bowman's layer microdistortions using OCT was developed to monitor corneal wound healing and improve lenticule extraction methods.

Accommodative changes after SMILE for moderate to high myopia correction

Background

To investigate accommodative response and accommodative lag changes after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction.

Methods

A total of 32 eyes of 32 patients with no strabismus who underwent SMILE were enrolled in this prospective clinical study. The accommodative response was obtained viewing monocularly with spherical equivalent refractive error corrected, using an open-field autorefractor at different stimulus levels (2.00D, 2.50D, 3.00D, 4.00D and 5.00D) for the right eye before a standard SMILE surgery and at 1-month follow-up after surgery.

Results

The mean age of the patients were 23.34 ± 2.90 years and the mean preoperative manifest refraction spherical equivalent was −5.74 ± 1.98 diopters. Significant differences were detected in both preoperative and postoperative accommodative responses to different stimulus levels (P < 0.001). Multiple linear regression model analysis revealed preoperative manifest refractive spherical equivalent (P = 0.006) and preoperative accommodative lag (P = 0.04) showed a significant impact on postoperative accommodative lag.

Conclusions

This is the first report of accommodative changes after SMILE. Our preliminary results showed that a decrease in postoperative accommodative lag that might be related to the relief of the visual discomfort symptom.

Chung's swing technique: a new technique for small-incision lenticule extraction

Background

To introduce the Chung’s swing technique for small-incision lenticule extraction (SMILE).

Methods

A total of 112 eyes of 56 patients were included in this study. Patients were divided into two groups: 52 eyes of 26 patients were treated with SMILE using a traditional method (traditional group) and 60 eyes of 30 patients were treated with SMILE using the Chung’s swing technique (swing group).

Results

At 1 month postoperatively, all eyes in both groups had an uncorrected distance visual acuity of 20/20 or better. The efficacy indices were 1.09 ± 0.17 and 1.02 ± 0.11 (p = 0.492), and the safety indices were 1.12 ± 0.14 and 1.09 ± 0.15 (p = 0.537), for the traditional and swing group, respectively. All eyes in both groups underwent successful lenticule extraction; all lenticules were intact and complete. The mean lenticule extraction times were 48.67 ± 4.9 and 39.8 ± 5.53 s, for the traditional and swing group, respectively (p < 0.001).

Conclusions

The Chung’s swing technique is efficient for lenticule separation and extraction. Our study results showed good clinical outcomes.

Trial registration

Trial registration number: KCT0001978. Registered 22 July 2016. Retrospectively registered.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-016-0321-2) contains supplementary material, which is available to authorized users.