Variation of Lenticule Thickness for SMILE in Low Myopia

First European results of a new refractive lenticular extraction procedure-SmartSight by SCHWIND eye-tech-solutions

BACKGROUND

To evaluate vision 3 months after SmartSight lenticule extraction treatments.

DESIGN

Case series.

METHODS

This case series of patients were treated at Specialty Eye Hospital Svjetlost in Zagreb, Croatia. Sixty eyes of 31 patients consecutively treated with SmartSight lenticule extraction were assessed. The mean age of the patients was 33 ± 6 years (range 23-45 years) at the time of treatment with a mean spherical equivalent refraction of -5.10 ± 1.35 D and mean astigmatism of 0.46 ± 0.36 D. Monocular corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) were assessed pre- and post-operatively. Ocular and corneal wavefront aberrations have been postoperatively compared to the preoperative baseline values. Changes in ocular wavefront refraction, as well as changes in keratometric readings are reported.

RESULTS

At 3 months post-operatively, mean UDVA was 20/20 ± 2. Spherical equivalent showed a low myopic residual refraction of -0.37 ± 0.58 D with refractive astigmatism of 0.46 ± 0.26 D postoperatively. There was a slight improvement of 0.1 Snellen lines at 3-months follow-up. Compared to the preoperative status, ocular aberrations (at 6 mm diameter) did not change at 3 months follow-up; whereas corneal aberrations increased (+0.22 ± 0.21 µm for coma; +0.17 ± 0.19 µm for spherical aberration; and +0.32 ± 0.26 µm for HOA-RMS). The same correction was determined using changes in ocular wavefront refraction, as well as changes in keratometric readings.

CONCLUSION

Lenticule extraction after SmartSight is safe and efficacious in the first 3 months postoperatively. The post-operative outcomes indicate improvements in vision.

Predictability of the Achieved Lenticule Thickness in Keratorefractive Lenticule Extraction for Myopia Correction

PURPOSE

To assess the predictability between the SCHWIND ATOS femtosecond laser (SCHWIND eye-tech-solutions) read-out and achieved lenticule thickness measured using MS-39 anterior segment optical coherence tomography (ASOCT; CSO) at the corneal vertex at postoperative 1 day and 1 and 3 months of follow-up.

METHODS

This retrospective case series included 130 eyes of 65 consecutive patients who were treated with SmartSight (SCHWIND eye-tech-solutions) lenticule extraction. Sixty-four percent of patients were women with a mean spherical refraction of -4.98 ± 1.19 diopters (D) and mean astigmatism of 0.53 ± 0.64 D. The measurements were performed using AS-OCT with the Phoenix Software v 4.1.1.5. Lenticule thickness was obtained by the subtraction method between preoperative and postoperative total corneal thickness.

RESULTS

A lower reduction in central corneal thickness (CCT) compared to the laser read-out for all three follow-up visits can be observed. Essentially, the reduction in CCT was identical at 3 months versus 1 month. The reduction in CCT was lowest at postoperative 1 day. Examining the 1- and 3-month data (essentially equivalent), one can see a best fit of y = 0.94 x -7 µm.

CONCLUSIONS

The reduction in CCT was stable from 1 month of follow-up. The stable reduction in CCT was -6% (-1.5% after accounting for design decisions) and -7 µm lower than the respective laser read-out. The findings are predictable, showing a certain level of the lenticules becoming slightly thinner than their respective laser read-outs. [J Refract Surg. 2023;39(11):728-735.].

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.].

Twelve-month outcomes of a new refractive lenticular extraction procedure

BACKGROUND

To evaluate the 12-month refractive and visual outcomes of Small Incision Guided Human-cornea Treatment (SmartSight®, SCHWIND eye-tech-solutions, Kleinostheim, Germany) in the treatment of myopia corrections with low to moderate astigmatism with the use of a new femtosecond laser system.

METHODS

221 eyes of 114 patients consecutively treated with SmartSight lenticule extraction were assessed. The mean age of the patients was 28±6 years at the time of treatment with a mean spherical equivalent refraction of -6.26±2.17D and mean astigmatism of 0.92±0.68D. Monocular corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) were assessed pre- and post-operatively. Refractive changes have been determined in terms of changes in refraction, as well as changes in keratometric readings. The changes in central epithelial thickness have been determined.

RESULTS

At twelve months post-operatively, mean UDVA was 20/21±2. Spherical equivalent showed a residual refraction of +0.48±0.31D with refractive astigmatism of 0.13±0.18D postoperatively. There was a slight decrease of -0.1 Snellen lines at 12-months follow-up. The same correction was determined using changes in refraction, as well as changes in keratometric readings. The central epithelial thickness increased by +3±2µm. Spherical equivalent correction within ±0.50D was achieved in 199 eyes (90%), and cylindrical correction in 221 (100%). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 213 eyes (96%), and postoperative uncorrected (UDVA) was 20/20 or better in 205 eyes (93%). No eye had lost two or more Snellen lines of CDVA.

CONCLUSIONS

Myopic astigmatism correction with SmartSight provided good results for efficacy, safety, predictability, and visual outcomes at the twelve months of follow up. The central epithelial thickness barely increased by 3±2µm.

Comparison of Changes in Corneal Thickness and Curvature After Myopia Correction Between SMILE and FS-LASIK

PURPOSE

To comparatively investigate the changes in corneal thickness and curvature between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).

METHODS

Data were collected preoperatively and postoperatively at 1 week, 1 month, and 3 months, including central corneal thickness (CCT), midperipheral corneal thickness (MPCT), peripheral corneal thickness (PCT), central keratometry (CK), midperipheral keratometry (MPK), and peripheral keratometry (PK), using a dual rotating Scheimpflug analyzer.

RESULTS

At 1 week postoperatively, changes in CCT, MPCT, PCT, and PK were significantly greater in the SMILE group than in the FS-LASIK group (P = .003 for CCT and < .001 for MPCT, PCT, and PK), but no significant inter-group differences were found between changes in CK and MPK (P = .883 and .513, respectively). CCT, MPCT, and PK values showed a similar increase in both groups, but significantly more increase in PCT and significantly less increase in CK and MPK was observed in the SMILE group from 1 week to 3 months after surgery. At 3 months postoperatively, CCT and MPCT were significantly thinner in the SMILE group than in the FSLASIK group (P = .018 and .022, respectively), and there was no significant difference in PCT, CK, MPK, and PK between the two groups.

CONCLUSIONS

SMILE caused significantly more corneal thinning at the center, midperiphery, and periphery, and more corneal flattening at the periphery, compared to FS-LASIK. A different pattern of corneal remodeling was observed between the two surgeries during the 3-month follow-up period. [J Refract Surg. 2023;39(1):15-22.].

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.].

Analysis of factors associated with unintended initial dissection of the posterior plane during small incision lenticule extraction

Background

To investigate potential risk factors for unintended initial dissection of the posterior plane in the initial learning curve of small incision lenticule extraction (SMILE).

Methods

Data were derived from consecutive 263 eyes of 136 patients who underwent SMILE at the beginning of the surgeon's learning curve. Probabilities of unintended initial dissection of the posterior plane in left and right eyes were analyzed. Preoperative sphere, cylinder, spherical equivalent (SE), J0, J45, lenticular diameter, lenticular thickness, corneal thickness, and axial length were assessed between eyes in which posterior plane dissection was unintended and those in which it was not.

Results

Unintended initial dissection of the posterior plane occurred in 29 eyes, corresponding to an incidence rate of 11.03%. The probability of difficulty in plane dissection in the left eye was significantly higher than that in the right eye (P=0.003). Significant differences were found in sphere (T =2.8, P=0.006), SE (T =2.37, P=0.019), J0 (T =2.05, P=0.043) and axial length (T =-2.79, P=0.006) between eyes with and without unintended initial dissection of the posterior plane.

Conclusions

In the present study, difficulty in plane dissection during SMILE was encountered significantly more often in left eyes for a right-hand doctor, and in eyes with low SE or high J0 values. Special attention should be paid to prevent unintended initial dissection of the posterior plane in such situations.

Customized Wavefront-Optimized Transepithelial Photorefractive Keratectomy for a Retained Lenticule Fragment After Primary SMILE

PURPOSE

To describe the surgical outcomes after transepithelial photorefractive keratectomy (PRK) for a case of retained intrastromal lenticule fragment after small incision lenticule extraction (SMILE).

METHODS

Transepithelial PRK was performed to minimize corneal irregularity and to correct residual refractive errors in a patient who had undergone failed lenticule extraction, which resulted in a refractive lenticule fragment being retained for 14 months after primary SMILE.

RESULTS

At the postoperative 6-month visit, uncorrected distance visual acuity and corrected distance visual acuity improved to 20/20 and 20/20, respectively, and corneal tomography depicted normalization of the corneal surface. Corneal higher order aberrations, including coma, trefoil, and spherical aberration, were markedly reduced.

CONCLUSIONS

Transepithelial PRK is a potential option for the management of a retained lenticule fragment after primary SMILE. [J Refract Surg. 2020;36(6):395-399.].

Enhancement Options After Myopic Small-Incision Lenticule Extraction (SMILE): A Review

PURPOSE

To provide an overview of the currently available retreatment methods after myopic small-incision lenticule extraction (SMILE).

DESIGN

Systematic literature review.

METHODS

The PubMed library was searched for articles containing the terms "small-incision lenticule extraction" and "enhancement" or "retreatment". The last search was performed on May 1, 2019.

RESULTS

In contrast to laser in-situ keratomileusis (LASIK), which can be retreated by a flap relift, repeat SMILE retreatment is currently not approved and only seldomly performed. As substitutes, surface ablation, cap-to-flap conversion using the CIRCLE program in the VisuMax platform, and thin-flap LASIK have been recently established. While all options offer safety and efficacy comparable to LASIK retreatments, each has its patient-specific advantages and disadvantages. While surface ablation preserves the flap-free approach of the primary procedure, the aspect of pain and a slow visual recovery might render it less attractive as compared with CIRCLE and thin-flap LASIK which offer quick recovery, however at the price of flap creation. Besides, each retreatment method generates specific tissue responses and has a different impact on corneal biomechanics, which is strongly dependent on the previous SMILE parameters, especially the cap thickness.

CONCLUSIONS

Refractive enhancement after SMILE is currently mostly performed by surface ablation, CIRCLE cap-to-flap conversion or thin-flap LASIK, which all offer safety and efficacy comparable to LASIK retreatments. In this review, a detailed overview over each method, its technical aspects, and specific advantages and disadvantages is given.