Suction stability management in small incision lenticule extraction: incidence and outcomes of suction loss in 4000 consecutive procedures

Refractive outcomes of small lenticule extraction (SMILE) Pro® with a 2 MHz femtosecond laser

PURPOSE

To evaluate the initial visual outcomes of Small Incision Lenticule Extraction (SMILE) Pro® using a 2 MHz femtosecond laser (VisuMax 800, Carl Zeiss Meditec) and to assess the efficacy, safety, predictability, accuracy, and complication rate.

METHODS

This retrospective analysis included eyes which underwent the SMILE Pro® procedure using VisuMax 800 femtosecond laser to correct myopia. All surgeries were performed by one surgeon (DB). Follow-up was conducted 3 months postoperatively to evaluate visual outcomes after neuroadaptation, corrected visual acuity (CDVA) and intra- and postoperative complications.

RESULTS

One hundred and fifty-two eyes of 82 patients (mean age 31 ± 6 years) results at 3 months are presented. The mean spherical equivalent (SE) was - 4.44 ± 1.86 D preoperatively while -0.24 ± 0.32 D postoperatively. 99% of eyes achieved SE within ± 1.0 D of attempted correction and 91% were within ± 0.5 D. Efficacy index was 0.93 while the safety index was 1. No complications occurred intra- or postoperatively. No eyes lost more than 1 line of their preoperative CDVA. All highly myopic eyes (- 6.25 to - 10.00 D; n = 18) achieved 20/20 at 3 months postoperatively and were within 0.5 D from the attempted SE and no eyes lost more than 1 line of CDVA.

CONCLUSION

The SMILE Pro® is a safe, efficient, and predictable procedure for the treatment of myopia and myopic astigmatism, with comparable results of conventional SMILE surgery. High myopic eyes achieve better results than low and moderate myopia. No complications were recorded in our patients.

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.

Refractive and Visual Outcomes of SMILE for Compound Myopic Astigmatism With the VISUMAX 800

PURPOSE

To report the first refractive and visual outcomes of small incision lenticule extraction (SMILE) using the VISUMAX 800 femtosecond laser (Carl Zeiss Meditec AG).

METHODS

This was a retrospective analysis of consecutive eyes treated by SMILE using the VISUMAX 800 femtosecond laser at London Vision Clinic, EuroEyes Group, London, United Kingdom. Inclusion criteria were patients aged younger than 45 years, a corrected distance visual acuity (CDVA) of 20/20 or better, and the 3-month postoperative timepoint data being available for analysis. Standard outcomes analysis and vector analysis by the Alpins method were performed.

RESULTS

During the study period, 128 eyes of 66 consecutive patients were treated. Three-month data were available for 118 eyes (92%), and 10 eyes (8%) were lost to follow-up. The mean attempted spherical equivalent refraction (SEQ) was -4.65 ± 1.91 diopters (D) (range: -1.90 to -10.05 D) and the mean cylinder was -0.98 ± 0.78 D (range: 0.00 to -4.00 D). The mean age was 30 ± 5 years (range: 20 to 43 years), with 54% women and 46% men. Postoperative SEQ was within ±0.50 D in 86% and ±1.00 D in 100% of eyes. Uncorrected distance visual acuity was 20/20 or better in 91% of eyes. One line of CDVA was lost in 8% of eyes, and no eyes lost two or more lines. There was a small but statistically significant increase in contrast sensitivity at 3, 6, 12, and 18 cpd.

CONCLUSIONS

Early outcomes data for SMILE with the second generation VISUMAX 800 femtosecond laser demonstrated an effective and safe option equivalent to published first generation VisuMax outcomes for the treatment myopia and astigmatism. [J Refract Surg. 2023;39(5):294-301.].

Grading for suction loss in small incision lenticule extraction

INTRODUCTION

To observe the characteristics of suction loss in small-incision lenticule extraction (SMILE) and analyze the factors affecting the stability of the suction ring, classify and grade suction loss, and determine the principles for its prevention and control.

METHODS

This study enrolled patients who underwent SMILE between June 2014 and June 2017. The relationship between the stability of the suction ring and suction loss was ascertained using surgical records and video recordings. The suction loss was classified and graded according to its characteristics and relationship with eye or head movement. The effect of target intervention on suction loss was observed.

RESULTS

Suction loss can be divided into sudden and progressive types. According to the severity, the latter was divided into three grades (grade 1A or 1B, 2 and 3). Of the 1200 eyes (608 patients), two (0.17%) had sudden suction loss, and 132 (11%) had progressive suction loss. The superior part, inferior part, and other parts accounted for 63.4%, 19.3%, and 17.3% of progressive suction loss, respectively. The proportion of grades 1A, 1B, 2, and 3 suction loss was 53%, 34%, 12%, and 1%, respectively. The location of the threatened suction loss was opposite to the direction of the patient's head movement. After the intraoperative intervention, grades 1 and 2 did not develop into "actual" suction loss.

CONCLUSIONS

Progressive suction loss was the most frequently observed suction loss during SMILE procedure. Grading suction loss can elucidate its underlying mechanism, which can guide targeted intervention measures to effectively control and reduce suction loss-induced damage, and further improve the safety and efficacy of SMILE.

SMILE for Hyperopia With and Without Astigmatism: Results of a Prospective Multicenter 12-Month Study

PURPOSE

To investigate the safety and effectiveness of small incision lenticule extraction (SMILE) in patients who have hyperopia with or without astigmatism.

METHODS

This was a prospective multicenter trial including 374 eyes of 199 patients treated by SMILE for hyperopia using the VisuMax femtosecond laser (Carl Zeiss Meditec AG). Inclusion criteria were sphere up to +6.00 diopters (D), cylinder up to 5.00 D, and maximum hyperopic meridian up to +7.00 D, with preoperative corrected distance visual acuity (CDVA) of 20/25 or better. The optical zone was 6.3 mm with a transition zone of 2 mm. The minimum lenticule thickness was set at 25 µm in the center and at 10 µm at the edge. Patients were examined at 1 day, 1 week, and 1, 3, 6, 9, and 12 months after surgery. Standard refractive surgery outcomes analysis was performed.

RESULTS

The preoperative spherical equivalent was +3.20 ± 1.48 D (range: +0.25 to +6.50 D). At the 12-month follow-up visit, 81% of eyes treated were within ±0.50 D and 93% of eyes were within ±1.00 D of intended correction. A total of 1.2% of eyes lost two or more lines of CDVA at the 12-month follow-up visit, and 83% were at least 20/20, corresponding to a safety index of 1.005 at 12 months. Of the 219 eyes with plano target, 68.8% had an uncorrected distance visual acuity of 20/20 or better and 88% were at least 20/25 uncorrected at 12 months. There were no statistically significant changes in contrast sensitivity.

CONCLUSIONS

SMILE was found to be an effective treatment method for the correction of compound hyperopic astigmatism, demonstrating a high level of efficacy, predictability, safety, and stability. [J Refract Surg. 2022;38(12):760-769.].

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.

Large Population Outcomes of Small Incision Lenticule Extraction in Young Myopic Patients

PURPOSE

To evaluate the outcomes of small incision lenticule extraction (SMILE) for myopia in a large population of young adults.

METHODS

In this retrospective case series, the patient population consisted of the first 4,138 consecutive SMILE treatments using the VisuMax femtosecond laser (Carl Zeiss Meditec) between 2012 and 2018 at the London Vision Clinic. Inclusion criteria were myopic spherical equivalent up to -9.00 diopters (D), cylinder up to 6.00 D, corrected distance visual acuity of 20/20 or better, age younger than 40 years, and follow-up of 12 months. Outcomes analysis was performed using the Standard Graphs for Reporting Refractive Surgery.

RESULTS

Data were available at 12 months in 3,722 eyes (90%), and 416 eyes (10%) were lost to follow-up. Mean attempted spherical equivalent refraction (SEQ) was -4.61 ± 1.84 D (range: -1.12 to -9.00 D). Mean cylinder was -0.78 ± 0.66 D (range: 0.00 to -6.00 D). Postoperatively, the mean SEQ relative to target was -0.13 ± 0.30 D (range: -1.35 to +1.25 D) and was within ±0.50 D in 88.1% and ±1.00 D in 99.6% of eyes. Uncorrected distance visual acuity was 20/20 or better in 95.4% of eyes and 20/25 or better in 98.7% of eyes. One line of CDVA was lost in 3.0% of eyes, and 0.08% (n = 3) lost two or more lines of CDVA, for which CDVA was restored following phototherapeutic keratectomy treatment. There was a statistically significant improvement of 0.05, 0.06, 0.07, and 0.07 log units for contrast sensitivity at 3, 6, 12, and 18 cycles per degree, respectively (P < .001).

CONCLUSIONS

SMILE achieved excellent outcomes for myopia up to -9.00 D with cylinder up to -5.50 D for a large population in patients without presbyopia. [J Refract Surg. 2022;38(8):488-496.].

Research Progress on Morphological Changes and Surgery-related Parameters of Corneal Cap in Small Incision Lenticule Extraction

Small incision lenticule extraction (SMILE) is an "all-in-one" surgical method for refractive correction. An advantage of the SMILE over traditional surgery is that it depends on the corneal cap's design. This review discusses the morphological evaluation of the corneal cap, selection of the corneal cap with different thickness and diameters, influence of the corneal cap design on retreatment, and management of corneal cap-related complications. The following points should be recognized to define the correct morphology and design of the operation-related parameters of the corneal cap during SMILE: (1) the thickness and diameter of the corneal cap are predictable and influence postoperative visual quality, (2) the change in anterior surface curvature of the corneal cap should be considered in the design of nomogram value, (3) for patients with moderate myopic correction, early visual quality is better with a 6.9-mm than with a 7.5-mm diameter corneal cap, (4) there is no significant difference in visual quality or biomechanics among corneal caps with different thickness; (5) primary corneal cap thickness plays an important role in the SMILE retreatment, (6) a 7.78-mm diameter corneal cap has a greater risk of suction loss than a 7.60-mm diameter corneal cap, (6) if suction loss occurs when lenticular scanning exceeds 10%, then SMILE can be continued by changing corneal cap thickness, (7) preventive collagen cross-linking with SMILE caps are 90-120 μm thick and 7-7.8 mm in diameter, and (8) properly treating SMILE-related complications ensures better postoperative results. The data presented herein shall deepen the understanding of the importance of the corneal cap during SMILE and provide diversified analysis for personalized operational design of corneal cap parameters.

Options and results in managing suction loss during small-incision lenticule extraction

Suction loss is an intraoperative complication in small-incision lenticule extraction (SMILE) that presents a management challenge for the refractive surgeon. The purpose of this review is to evaluate the visual, refractive, and wavefront outcomes after suction loss across the different stages of SMILE with various respective surgical treatments. Surgical management options include immediate re-SMILE by redocking or delayed re-SMILE, with or without adjustment of the laser parameters, conversion to femtosecond laser in situ keratomileusis, transepithelial photorefractive keratectomy, refractive lenticule extraction, or pseudo-SMILE. The restart treatment module on VisuMax provides appropriate retreatment recommendation. Most retreatment options for suction loss, immediate or delayed, resulted in effective, safe, and predictable outcomes, and patients were satisfied with their outcomes. Based on available level II evidence, immediate re-SMILE with or without adjustment to the laser settings achieve favorable visual and refractive outcomes in handling this intraoperative complication across all stages of SMILE.

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.

Complications of small incision lenticule extraction

The procedure of small incision lenticule extraction (SMILE) was introduced in 2011, and since then there has been an increase in the number of cases undergoing this procedure worldwide. The surgery has a learning curve and may be associated with problems in the intraoperative and postoperative periods. The intraoperative problems during SMILE surgery include the loss of suction, the occurrence of altered or irregular opaque bubble layer and black spots, difficulty in lenticular dissection and extraction, cap perforation, incision-related problems, and decentered ablation. Most of the postoperative problems are similar as in other laser refractive procedures, but with decreased incidence. The identification of risk factors, clinical features, and management of complications of SMILE help to obtain optimum refractive outcomes.

SMILE – Small Incision Lenticule Extraction

Die SMILE (small incision lenticule extraction) zählt zu den Verfahren der refraktiven Lentikel-Extraktion und hat sich im letzten Jahrzehnt zu einem etablierten Bestandteil des modernen refraktivchirurgischen Spektrums entwickelt. Dieser Beitrag gibt einen Überblick über Patientenselektion, Operationsmethode, mögliche Komplikationen und klinische Ergebnisse dieser Methode.

[SMILE - Small Incision Lenticule Extraction]

Refractive lenticule extraction is a corneal surgical technique that uses a femtosecond laser exclusively to create an intrastromal refractive lenticule for the correction of myopia and myopic astigmatism. In small incision lenticule extraction (SMILE) the generated refractive lenticule is subsequently extracted through a small incision. The reported efficacy, predictability and safety of the flap-less SMILE procedure is similar to those of femtosecond laser in situ keratomileusis (LASIK). Advantages of SMILE over LASIK include less iatrogenic dry eye, fewer induced higher-order aberrations, and potentially less biomechanical weakening of the cornea. However, there is a steeper surgeon learning curve for SMILE as the procedure is technically more challenging than LASIK. Furthermore, the current SMILE laser platform cannot use cyclotorsion control or eye-tracking technology and retreatment options are more complex compared to LASIK. This review looks at patient selection, surgical method, possible complications, retreatment options, and postoperative outcome of the SMILE technique.

Risk factors and incidence of suction loss during small incision lenticule extraction (SMILE) in 8493 eyes

BACKGROUND

To report the incidence and risk factors of suction loss during small incision lenticule extraction (SMILE).

METHODS

This retrospective comparative case control study included 8493 eyes of 4261 patients. Patients underwent SMILE surgery between January 2014 and September 2019 were included. Videos of suction loss were reviewed, and the direct causes of suction loss were noted. An independent samples t-test was used for comparisons between the suction loss group and the control group. A binary logistic regression model was used to determine the possible significant risk factors that might increase the likelihood of suction loss during SMILE surgery.

RESULTS

Suction loss occurred in 31 (0.37%) eyes of 30 patients; 23 (74.2%) cases occurred in the right eye (the first operative eye) and 8 (25.8%) cases occurred in the left eye. Among the 30 patients, 23 (76.7%) were male and 7 (23.3%) were female. The incidence in the six consecutive years were 0, 2.13, 0.34, 0.24, 0.22, and 0.25%. Head and eye movements during surgery caused suction loss in 16 (51.6%) and 15 (48.4%) eyes, respectively. Comparison between the suction loss group and the control group showed that the first operative eye and male sex are at a significantly high risk for suction loss (p < 0.05).

CONCLUSIONS

The risk factors of suction loss were first operative eye and male sex. Head and eye movements due to patient anxiety are the most common direct causes of suction loss. Surgeon's experience may help to reduce the incidence of suction loss. Preoperative education and better communication during surgery needs to be emphasized.

TRIAL REGISTRATION

Retrospectively registered. ChiCTR-ORC-17011040 . Registered 1 April 2017. Name of registry: The observation of clinical results after corneal refractive surgery. Data of enrolment of the first participant to the trial: 1 January 2014.

Refractive surgery beyond 2020

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.