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Representative SEM micrographs showing the remaining stroma after the lenitcule extraction by different instruments in the non-optimizing laser setting. The remaining stroma after the lenticule extraction remained intact, without damage caused by the instruments. Magnification 200x, scale bar: 100 µm.
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Small incision lenticule extraction (SMILE) is an alternative to Laser-Assisted in situ Keratomileusis (LASIK) for correction of myopia. In cases where surgeons inadvertently dissect the posterior surface first, identification of the anterior surface and subsequent removal become difficult since the anterior surface of the lenticule is compacted ag...
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Background:
Small incision lenticule extraction (SMILE) and femtosecond laser in situ keratomileusis (FS-LASIK) have been extensively studied as the main surgical methods for corneal refractive surgery. However, there is no consensus on whether SMILE is superior to FS-LASIK in corneal biomechanics. Therefore, this systematic review and meta-analys...
Purpose:
To compare the clinical outcomes of small incision lenticule extraction (SMILE) and wavefront-guided LASIK (WFG LASIK) in eyes with low and moderate myopia.
Methods:
This was a prospective, comparative study enrolling 110 eyes with low and moderate myopia (spherical equivalent ≤ 6.00 diopters [D]). Two groups were differentiated accordi...
Purpose The aim of this study was to compare the differences in corneal biomechanical changes after laser-assisted in situ keratomileusis (LASIK) and femtosecond laser small-incision lenticule extraction (SMILE) using the corneal visualization Scheimpflug technology (Corvis ST).
Patients and methods This is a prospective study that included two gro...
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Citations
... The procedure entails forming lower and upper lenticule interfaces and a 2-3 mm incision for lenticule extraction. FDA-approved for myopia correction, SMILE stands as a cost-effective alternative to LASIK, requiring only a single laser platform [16,17]. SMILE demonstrates comparable safety, efficacy, and predictability outcomes to LASIK, with heightened patient satisfaction and diminished postoperative dry eye incidence. ...
... Notably however, among the 3 cases that exhibited partially rough surfaces, in 2 cases it was related to the posterior surface and in only 1 case it was related to the anterior surface The results suggested that dissection between the lenticule-stromal bed interface could be more difficult than dissection at the cap-lenticule interface: the anterior surface can be dissected under the cap smoothly, but for the posterior surface, dissection was done more slowly and involved repetition action because the lenticule was thin and unfixed. This emphasizes the importance of good cooperation and careful surgical manipulation during the procedure, for both hyperopia and myopia correction [17]. Visible cavitation holes were absent in all lenticules except 1 in the myopia group that exhibited a few cavitation holes on the anterior surface. ...
Background:
To evaluate lenticule surface characteristics of small incision lenticule extraction (SMILE) for hyperopia correction in rabbits.
Methods:
The left and right eyes of 8 rabbits were divided into two groups. The right eyes were assigned to a myopia group, and the left eyes to a hyperopia group. The rabbits received SMILE procedures with + 3.00 D and - 3.00 D correction for the hyperopia and myopia groups, respectively. Extracted lenticules were examined via scanning electron microscopy. Lenticules from odd-numbered rabbits were accessed with the anterior surface, and lenticules from even-numbered rabbits were observed with the posterior surface. A previously established scoring system was used to evaluate lenticule surface characteristics. Statistical analysis was conducted to compare the scores between the two groups.
Results:
All procedures were performed successfully, and the lenticules were extracted smoothly. One myopia lenticule that was facing downward was handled failed in preparation for imaging, thus 15 lenticules were ultimately graded. Twelve lenticules exhibited smooth surfaces, and regularly arranged tissue bridges were observed in almost all regions. Three lenticules exhibited a partially rough surface and irregularities affecting more than 10% of the lenticules (2 in the hyperopia group and 1 in the myopia group). Rough lenticules occurred in twice as many lenticules in the hyperopia group compared to the myopia group.
Conclusions:
Scan quality of lenticules after SMILE for hyperopia correction is comparable to that of myopia lenticules. The shape of hyperopic lenticule may increase the difficulty of surgical manipulation and result in surface roughness.
... This emphasizes the importance of good cooperation and careful surgical manipulation during the procedure, for both hyperopia and myopia correction. [17] Visible cavitation holes were absent in all lenticules except 1 in the myopia group that exhibited a few cavitation holes on the anterior surface. Cavitation holes are gas bubbles formed during the vaporization of the corneal tissue, and they affect scanning quality. ...
Background: To evaluate lenticule surface characteristics of small incision lenticule extraction (SMILE) for hyperopia correction in rabbits.
Methods: The left and right eyes of 8 rabbits were divided into two groups. The right eyes were assigned to a hyperopia group, and the left eyes to a myopia group. The rabbits received SMILE procedures with +3.00 D and –3.00 D correction for the hyperopia and myopia groups, respectively. Extracted lenticules were examined via scanning electron microscopy. Lenticules from odd-numbered rabbits were accessed with the anterior surface, and lenticules from even-numbered rabbits were observed with the posterior surface. A previously established scoring system was used to evaluate lenticule surface characteristics. Statistical analysis was conducted to compare the scores between the two groups.
Results: All procedures were performed successfully, and the lenticules were extracted smoothly. One myopia lenticule that was facing downward was handled failed in preparation for imaging, thus 15 lenticules were ultimately graded. Twelve lenticules exhibited smooth surfaces, and regularly arranged tissue bridges were observed in almost all regions. Three lenticules exhibited a partially rough surface and irregularities affecting more than 10% of the lenticules (2 in the hyperopia group and 1 in the myopia group). Rough lenticules occurred in twice as many Lenticules in the hyperopia group compared to the myopia group.
Conclusions: Scan quality of lenticules after SMILE for hyperopia correction is comparable to that of myopia lenticules. The shape of hyperopic lenticule may increase the difficulty of surgical manipulation and result in surface roughness.
... However, SMILE also has higher demands for the operator and a steeper learning curve than does traditional LASIK surgery [3]. It is also difficult to perform due to the optical lens being too thin for low myopia [4]. Moreover, due to the limitations of femtosecond lasers, the lens may still have a tissue bridge connection with adjacent tissues, resulting in partial lens separation difficulty, intraoperative epithelial damage, incision tears, and other complications [5]. ...
To investigate the effect of corneal stromal pocket irrigation after small-incision lenticule extraction (SMILE) on visual acuity, intraocular pressure (IOP), corneal parameters and complications after surgery.
A total of 242 eyes of 121 patients undergoing SMILE were enrolled in this prospective controlled study, and it was designed for one eye to randomly undergo SMILE with balanced salt solution irrigation of the corneal stromal pocket, while the other eye was not. The uncorrected distance visual acuity (UDVA) and slit lamp examination were recorded at 1 hour, 1 day, 1 week, and 1 month. Postoperative corneal density, corneal biomechanical, corneal endothelial cell number, and anterior OCT images were compared at 1 day, 1 week, and 1 month.
Compared with the nonirrigation group, the irrigation group showed significantly higher UDVA at 1 day postoperatively (P < 0.05), but there was no significant difference during the rest of the postoperative period (1 hour, 1 week, and 1 month). In addition, no significant differences were found in IOP, corneal density, corneal biomechanics, corneal endothelial cells, and corneal morphology. No visual decline or severe postoperative complications were found in the patients in this study.
Interlamellar irrigation did not affect IOP, corneal parameters, morphology, complications, or UDVA at 1 hour, 1 week, and 1 month after the operation, but it may promote UDVA 1 day after the operation.
... This emphasizes the importance of good cooperation and careful surgical manipulation during the procedure, for both hyperopia and myopia correction. [17] Visible cavitation holes were absent in all lenticules except 1 in the myopia group that exhibited a few cavitation holes on the anterior surface. Cavitation holes are gas bubbles formed during the vaporization of the corneal tissue, and they affect scanning quality. ...
Purpose: To evaluate lenticule surface characteristics of small incision lenticule extraction (SMILE) for hyperopia correction in rabbits. Methods: The left and right eyes of 8 rabbits were divided into two groups. The right eyes were assigned to a hyperopia group, and the left eyes to a myopia group. The rabbits received SMILE procedures with +3.00 D and –3.00 D correction for the hyperopia and myopia groups, respectively. Extracted lenticules were examined via scanning electron microscopy. Lenticules from odd-numbered rabbits were accessed with the anterior surface, and lenticules from even-numbered rabbits were observed with the posterior surface. A previously established scoring system was used to evaluate lenticule surface characteristics. Statistical analysis was conducted to compare the scores between the two groups. Results: All procedures were performed successfully, and the lenticules were extracted smoothly. One myopia lenticule that was facing downward was handled failed in preparation for imaging, thus 15 lenticules were ultimately graded. Twelve lenticules exhibited smooth surfaces, and regularly arranged tissue bridges were observed in almost all regions. Three lenticules exhibited a partially rough surface and irregularities affecting more than 10% of the lenticules (2 in the hyperopia group and 1 in the myopia group). Rough lenticules occurred in twice as many Lenticules in the hyperopia group compared to the myopia group. Conclusions: Scan quality of lenticules after SMILE for hyperopia correction is comparable to that of myopia lenticules. The shape of hyperopic lenticule may increase the difficulty of surgical manipulation and result in surface roughness.
... This emphasizes the importance of good cooperation and careful surgical manipulation during the procedure, for both hyperopia and myopia correction. [17] Visible cavitation holes were absent in all lenticules except 1 in the myopia group that exhibited a few cavitation holes on the anterior surface. Cavitation holes are gas bubbles formed during the vaporization of the corneal tissue, and they affect scanning quality. ...
Background: To evaluate lenticule surface characteristics of small incision lenticule extraction (SMILE) for hyperopia correction in rabbits.
Methods: The left and right eyes of 8 rabbits were divided into two groups. The right eyes were assigned to a hyperopia group, and the left eyes to a myopia group. The rabbits received SMILE procedures with +3.00 D and –3.00 D correction for the hyperopia and myopia groups, respectively. Extracted lenticules were examined via scanning electron microscopy. Lenticules from odd-numbered rabbits were accessed with the anterior surface, and lenticules from even-numbered rabbits were observed with the posterior surface. A previously established scoring system was used to evaluate lenticule surface characteristics. Statistical analysis was conducted to compare the scores between the two groups.
Results: All procedures were performed successfully, and the lenticules were extracted smoothly. One myopia lenticule that was facing downward was handled failed in preparation for imaging, thus 15 lenticules were ultimately graded. Twelve lenticules exhibited smooth surfaces, and regularly arranged tissue bridges were observed in almost all regions. Three lenticules exhibited a partially rough surface and irregularities affecting more than 10% of the lenticules (2 in the hyperopia group and 1 in the myopia group). Rough lenticules occurred in twice as many Lenticules in the hyperopia group compared to the myopia group.
Conclusions: Scan quality of lenticules after SMILE for hyperopia correction is comparable to that of myopia lenticules. The shape of hyperopic lenticule may increase the difficulty of surgical manipulation and result in surface roughness.
... Special instruments have been developed to assist in this task. 12 Because the correction of low refractive errors results in increasingly low minimum lenticule thickness and thus thin lenticule borders, their safe delineation, dissection, and removal can not only pose a great challenge for SMILE novices, but may also lead to an increase in intraoperative complications in experienced surgeons. Therefore, common experience suggests either enlargement of the optical zone or a deliberate increase in minimum lenticule thickness to enhance surgical ease and safety. ...
Purpose:
To report the impact of increasing minimum lenticule thickness on the safety and efficacy of small incision lenticule extraction (SMILE) in low myopia up to -3.50 diopters (D).
Methods:
SMILE was performed in 76 eyes of 76 patients. Thirty-eight eyes of 38 patients with low myopia were prospectively operated on with a programmed minimum lenticule thickness of 15 to 30 μm (thicker lenticule group). Thirty-five eyes suitable for analysis were then retrospectively matched by spherical equivalent to 35 eyes operated on with a minimum standard setting of 10 μm (standard thickness group), as provided in the database of the SMILE Eyes Clinic Linz, Linz, Austria. Comparison of outcomes was performed with the Standard Graphs for Reporting Refractive Surgery and by analysis of higher order aberrations as provided by Scheimpflug imaging.
Results:
Apart from lenticule thickness, there was no significant difference in preoperative baseline or treatment parameters between both groups. Mean minimum lenticule thickness differed significantly (standard thickness = 10 ± 0 μm; thicker lenticule = 20 ± 5 μm; P < .0001). This also translated into a significant difference in maximum lenticule thickness (standard thickness: 54 ± 11 μm; thicker lenticule: 62 ± 8 μm; P = .0002). Mean SEQ preoperatively was -2.25 ± 0.51 (standard thickness) and -2.24 ± 0.46 (thicker lenticule) D, respectively, and changed to -0.11 ± 0.50 (standard thickness) and +0.01 ± 0.36 (thicker lenticule) D postoperatively (P < .0001 for both comparisons). Uncorrected postoperative visual acuity was -0.08 ± 0.35 (standard thickness) versus -0.10 ± 0.09 (thicker lenticule) logMAR (P = .706). After SMILE, the thicker lenticule group showed better safety (1.20 vs 1.08; P = .025) and efficacy (1.14 vs 0.96; P = .011) indices, translating into more eyes within ±0.50 D from target (91% vs 77%) and with at least 0.0 logMAR visual acuity (97% vs 86%), and fewer eyes losing one (3% vs 17%) and two (0% vs 3%) lines.
Conclusions:
Increasing minimum lenticule border thickness seems to improve the safety and efficacy of SMILE in low myopia. [J Refract Surg. 2018;34(7):453-459.].
... Previously, our knowledge and understanding of the wound ultrastructure after SMILE was mainly derived from studying the surface quality of extracted human lenticules 10-12 and from animal models. 13,14 To our knowledge, the current study is the first to image the SMILE incision architecture and the surface texture of the lenticule bed after SMILE in human donor corneas by means of SEM. Although the SMILE incisions displayed sharp and uniform stromal edges, the surface texture of the stromal lenticule bed had a more irregular appearance with more fringed collagen lamellae when compared to stromal beds after FS-LASIK. ...
Purpose:
To assess the wound healing, inflammation, and tissue ultrastructure in the human corneal stroma after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK).
Methods:
Sixteen corneoscleral discs of 16 human donors unsuitable for corneal transplantation were obtained from an eye bank. Eight eyes underwent SMILE with -5.00 diopters (D) of myopic correction; in 3 of them the lenticule was not extracted. Further 5 donor corneas were subjected to FS-LASIK with -5.00 D ablation, and 3 eyes served as the control group without surgical intervention. Postoperatively, specimens were incubated in organ culture medium for 72 hours before being subjected to immunofluorescence staining for CD11b, Ki67, fibronectin, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay, and high-magnification scanning electron microscopy.
Results:
Keratocyte apoptosis, keratocyte proliferation, and infiltration of immune cells were generally mild and comparable between FS-LASIK and SMILE (irrespective of surgical lenticule extraction). By staining for fibronectin, we observed a trend toward milder fibrotic response in the corneal stroma after SMILE than after FS-LASIK. On the contrary, scanning electron microscopy analysis revealed a smoother, more regular ultrastructural appearance of the residual corneal bed after FS-LASIK.
Conclusions:
Corneal stromal wound healing after SMILE and FS-LASIK was virtually identical with respect to keratocyte proliferation and apoptosis in the human donor eye model. Although reactive fibrosis adjacent to the laser application site appeared less marked after SMILE, the stromal bed after LASIK exhibited a smoother surface texture. [J Refract Surg. 2018;34(6):393-399.].
... SMILE was performed by the same surgeon (JSM) using a 500 kHz VisuMax Femtosecond (FS) laser (Carl Zeiss Meditec, Jena, Germany). All SMILE procedures were for myopic treatment as previously described [22,23]. The mean patient age was 31.2 ± 7.30 years, and the mean spherical equivalent refractive correction was −6.0 ± 1.8 diopters. ...
Purpose
To explore the optimal lenticule storage conditions that maintain lenticule integrity and clarity.
Methods
A total of 99 lenticules obtained from myopic patients undergoing small incision lenticule extraction (SMILE) were divided into four combinations for short-term storage conditions: PBS, Dulbecco’s Modified Eagle’s Medium (DMEM), Optisol GS, or anhydrous glycerol. Two thirds of the lenticules were further stored for 4 weeks under eight different conditions. Clarity evaluation with transmittance measurements, cell-death assays with terminal deoxynucleotidyl transferase-mediated nick end labeling assay (TUNEL), collagen fibril spacing and necrotic response assessed with transmission electron microscopy (TEM), and immunohistochemistry analysis for human leukocyte antigens (HLAs) and CD45 for immunogenicity, and matrix metalloproteinase (MMP)-2 for keratocyte response, were undertaken at baseline, 48 h (short term), and 4 weeks (long term).
Results
The TUNEL and immunogenicity results were comparable among the groups. The mean percentage of TUNEL-positive cells across all groups was 24.3% ± 11.8% and 62.9% ± 20.7% at the 48 h and 4 week time points, respectively. HLA-ABC+, HLA-DR+, and CD45+ cells were extremely rare, and MMP-2 expression ranged from non-detectable to minimal, under all conditions at all time points. Transmittance at 4 weeks was significantly different among groups with the greatest maintenance of clarity seen in the lenticules stored initially in DMEM at 4 °C for 48 h followed by cryopreservation in serum-free medium or glycerol at 4 °C followed by storage at room temperature. At TEM analysis at 4 weeks, the lenticules cryopreserved in liquid nitrogen, regardless of storage solutions, had significantly narrower inter-fibrillar distance than controls, while glycerol-preserved lenticules, at either room temperature or −80 °C, maintained the inter-fibrillar distance.
Conclusions
Clarity, structural integrity, and low immunogenicity under various conditions, at 4 °C or room temperature for short-term storage, offer encouragement for lenticule storage. It can be undertaken without access to s specialized and potentially expensive laboratory setup at least within the first 48 h before transportation to larger facilities for long-term storage.
... To minimize secondary injuries after an OBL, surgeons should avoid using sharp instruments and forceful dissection. 26 An unintended posterior plane dissection occurred in 0.33% of our cases. The anterior plane of the lenticule was commonly dissected first so that the posterior plane of the lenticule could be found easily. ...
Purpose
To assess the intraoperative complications during small-incision lenticule extraction (SMILE) for myopia and myopic astigmatism correction and evaluate visual outcomes 6 months postoperatively.
Setting
Tianjin Eye Hospital, Tianjin, China.
Design
Retrospective case series.
Methods
Patients who had small-incision lenticule extraction surgery were examined 1 day, 7 days, 1 month, 3 months, and 6 months postoperatively. Demographic characteristics, visual outcomes, and intraoperative complications were recorded. Moreover, the incidence and management of the complications and the potential factors were analyzed.
Results
Of the 3004 eyes (1511 patients), 134 (4.46%) had intraoperative complications, including suction loss (28 cases [0.93%]), incisional bleeding (28 cases [0.93%]), opaque bubble layer (22 cases [0.73%]), subconjunctival hemorrhage (20 cases [0.67%]), black areas (10 cases [0.33%]), unintended posterior plane dissection (10 cases [0.33%]), tearing of the lenticule (8 cases [0.27%]), abrasion at the incision (5 cases [0.17%]), and inaccurate laser pulse placement due to eye movement (3 cases [0.10%]). The complications were resolved instantaneously using appropriate management procedures; all cases had good visual outcomes. Six months postoperatively, 99.80% of cases had an uncorrected distance visual acuity better than 20/25 and the mean corrected distance visual acuity was −0.06 logarithm of the minimum angle of resolution ± 0.07 (SD).
Conclusions
Although small-incision lenticule extraction shows promising outcomes for correction of myopia and myopic astigmatism, intraoperative complications still inevitably occur. However, satisfactory visual outcomes may be achieved using appropriate management techniques.
