In vivo confocal laser microscopy of morphologic changes after small incision lenticule extraction with accelerated cross-linking (SMILE Xtra) in patients with thin corneas and high myopia.

PURPOSE: To evaluate the microstructural modifications and safety of small incision lenticule extraction combined with accelerated cross-linking (SMILE Xtra) in high myopia and thin corneas by means of in vivo confocal microscopy (IVCM) and 3D-OCT after a 6-month follow-up. METHODS: Forty-three eyes with high myopia and thin corneas were enrolled. All eyes underwent SMILE procedure. After the lenticule was extracted, 0.25% riboflavin was injected into the interface and allowed to diffuse for 60 s. The eye was irradiated with UVA radiation of 30 mW/cm2 for 90 s through the cap. The total energy delivered was 2.7 J/cm2. Morphologic modifications of corneal architecture were evaluated prior to SMILE Xtra and 7 days, 1, 3, and 6 months after SMILE by in vivo confocal microscopy (IVCM) and 3D-OCT. RESULTS: The corneal epithelial cells showed slight damage until 3 months postoperatively. The subepithelial nerve plexus decreased but no absence within the treatment zone at the first week after treatment, recolonized at 3 months postoperatively, and had mostly recovered at the 6 months postoperative but remained less than its normal baseline state. Keratocytes were absent in the surgical interface area, and the presence of strong reflective particles and cicatricial reaction in the anterior stroma were observed during the entire 6-month examination period. Increased hyperreflectivity was observed from the cap side at a depth of 60 µm to stroma bed at a depth of 388 µm through 6 months. The depth of the demarcation line in 40 eyes (93.0%) was at a mean depth of 296.12 ± 47.86 µm (range, 211-388 µm). No particular change between preoperative and postoperative corneal endothelium was observed. CONCLUSIONS: Confocal microscopy showed increased hyperreflectivity in the SMILE Xtra eyes, and no changes in corneal endothelium. We confirmed the safety of the SMILE Xtra but recognize that larger and longer-term studies of SMILE Xtra are necessary.

Revealing the Impact of Dual Site Modification on the Phase Transformation and Ion Transport Mechanism of Ni-Rich Cathode Materials.

Ni-rich cathode materials have garnered significant attention attributable to the high reversible capacity and superior rate performance, particularly in the electric vehicle industry. However, the structural degradation experienced during cycling results in rapid capacity decay and deterioration of the rate performance, thereby impeding the widespread application of Ni-rich cathodes. Herein, a Mg/Ti co-doping strategy was developed to boost the structure stability and Li-ion transport kinetics of the Ni-rich cathode material LiNi0.90Co0.05Mn0.05O2 (NCM9055) under long cycle. It is demonstrated that the Mg2+ ions inserted into the lithium layer could serve as pillars, enhancing the stability of the delithiated layer structure. The introduction of robust Ti-O bonding mitigated the detrimental H2-H3 phase transition (∼4.2 V) during cycling. In addition, despite the fact that Mg/Ti co-doping slightly reduces Li+ diffusion coefficient in the modified cathode material (NCM9055-MT), it effectively stabilized the robustness of the layered structure and maintained the Li+ diffusion channel while charging and discharging, thereby improving the Li+ diffusion coefficient after a long cycle. Therefore, the Mg/Ti co-doped cathode materials exhibited an exceptional capacity retention rate of 99.9% (100 cycles, 1 C). Additionally, the Li+ diffusion coefficient of the co-doped NCM9055-MT (2.924 × 10-10 cm2 s-1) after 100 cycles was effectively enhanced compared with the case of undoped NCM9055 (4.806 × 10-11 cm2 s-1). This work demonstrates that the Mg/Ti co-doping approach effectively enhanced the stability of layered Ni-rich cathode materials.

Safety and Efficacy of Corneal Minimized-Volume Ablation With Accelerated Cross-Linking in Improving Visual Function for Keratoconus.

PURPOSE: To evaluate the safety and efficacy of corneal minimized-volume ablation with accelerated cross-linking in improving visual function in keratoconus eyes. METHODS: Through a pilot study, 25 eyes of 25 consecutive patients with keratoconus grade I-III were recruited that underwent corneal transepithelial photorefractive keratectomy with "minimized volume" ablation profile and accelerated corneal cross-linking in the same session. Corrected and uncorrected distance visual acuities, manifest refraction, corneal curvature and higher-order aberrations, endothelial cells, and the ocular modulation transfer function were assessed preoperatively and postoperatively, with a minimum follow-up of 6 months. A P value < 0.05 was the threshold of statistical significance. RESULTS: At 8.2 ± 3.6 months postoperatively, the mean corrected and uncorrected distance visual acuities (LogMAR) were 0.07 ± 0.15 and 0.45 ± 0.39, significantly improving from the baseline of 0.24 ± 0.24 (P8m-before = 0.005) and 1.12 ± 0.33 (P8m-before < 0.001), respectively. Spherical equivalent was -2.80 ± 2.72 diopters (D), significantly decreasing from the baseline of -6.61 ± 3.06 D (P8m-before < 0.001), whereas the attempted corrected spherical equivalent was-2.30 ± 1.22 D. Meanwhile, a significant reduction was found in higher-order aberration, along with the postoperative improvement in ocular modulation transfer function. Corneal surface morphological parameters were found with significant decreases postoperatively (index of surface variance: P8m-before = 0.003; index of vertical asymmetry: P8m-before = 0.005; keratoconus index: P8m-before = 0.004; center keratoconus index: P8m-before = 0.003; and index of height decentration: P8m-before < 0.001). Nevertheless, no significant change was found in posterior corneal curvature or endothelial cell density between pre- and post-operative periods. CONCLUSIONS: Corneal minimized-volume ablation with accelerated cross-linking was an effective and safe option for correction of mild refractive error, leading to significant improvement of visual function in patients with keratoconus.

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

PURPOSE: To evaluate the vector outcomes of small incision lenticule extraction (SMILE) in correcting moderate to high myopic astigmatism under astigmatic axis marked condition. METHODS: In a prospective, longitudinal, interventional study, 71 eyes (71 patients) that had with-the-rule preoperative cylinder refraction exceeding 1.50 diopters (D) were corrected with the VisuMax femtosecond laser (Carl Zeiss Meditec AG) at Zhongshan Ophthalmic Center. Refractive outcomes and astigmatic vector were evaluated preoperatively and at 1, 3, 6, and 30 months postoperatively. RESULTS: At 30 months postoperatively, the efficacy and safety indexes were 1.04 ± 0.18 and 1.15 ± 0.17, respectively. The magnitude of the surgically induced astigmatism (SIA) (2.13 ± 0.71 D at 1 month [P1m-pre = .018], 2.12 ± 0.72 D at 3 months [P3m-pre = .006], 2.13 ± 0.69 D at 6 months [P6m-pre = .010], and 2.19 ± 0.72 D at 30 months [P30m-pre < .001]) was slightly higher than that of the target induced astigmatism (TIA) (2.07 ± 0.69 D). Only the y-coordinate of the SIA vector had a significant overcorrection compared to that of the TIA vector (P1m-pre = .033, P3m-pre = .011, P6m-pre = .012, P30m-pre < .001). The corrected index (CI = |SIA|/|TIA|) varied from 1.03 ± 0.07 at 1 month to 1.06 ± 0.10 at 30 months, which was higher when correcting moderate astigmatism than when correcting high astigmatism (P = .041) at 30 months postoperatively. CONCLUSIONS: SMILE had long-term safety, efficacy, predictability, and stability when correcting moderate to high myopic astigmatism under astigmatism axis marked condition. Meanwhile, a cylinder overcorrection was observed due to the overcorrection of y-coordinate astigmatic power, which implied that the vector adjustment of the cylinder refraction nomogram should be considered. [J Refract Surg. 2020;36(9):585-591.].

Development of low laser energy levels in small-incision lenticule extraction: clinical results, black area, and ultrastructural evaluation.

PURPOSE: To evaluate the outcomes of 4 low laser energy levels after small-incision lenticule extraction (SMILE) surgery. SETTING: Zhongshan Ophthalmic Center, Guangzhou, China. DESIGN: Prospective randomized clinical trial. METHODS: This study evaluated consecutive patients who had SMILE to correct myopia or myopia with astigmatism. Eyes were placed into groups based on the laser energy used during surgery (ie, 105 nJ, 110 nJ, 115 nJ, or 120 nJ). All patients had a thorough ophthalmic examination preoperative and at 4 timepoints over 3 months postoperatively. Black areas and surface regularity of the extracted lenticules were observed and evaluated qualitatively and quantitatively. RESULTS: The study comprised 124 eyes of 62 patients (40 women, 22 men), with 31 eyes in each laser energy group. The incidence of black areas was 45.16% (14 of 31 eyes), 12.90% (4 of 31 eyes), 16.13% (5 of 31 eyes), and 12.90% (4 of 31 eyes) for 105 nJ, 110 nJ, 115 nJ, and 120 nJ, respectively. The mean time for lenticule creation was the longest in the 105 nJ group (P = .015). The greatest increase in corneal thickness postoperatively occurred with 105 nJ (P < .05). Regression was highest in the 105 nJ group at 3 months (P < .01). However, corneal horizontal coma (C8) was lowest in the 105 nJ group at 1 week (P = .032). The lenticular surface in the 110 nJ group was the smoothest (P = .011). All contrast sensitivity values varied with time and recovered to preoperative levels by 1 week or 1 month. In all eyes, the uncorrected distance visual acuity and corrected distance visual acuity were good, with no statistically significant differences between the 4 energy groups. CONCLUSIONS: The 105 nJ group, in which the lowest energy was used, had the highest risk for black areas, serious postoperative corneal edema, and a significant healing response.

Optimal Parameters of Scanning Mode in Small Incision Lenticule Extraction (SMILE): Clinical Results and Ultrastructural Analysis.

PURPOSE: To compare the effect of two scanning modes with different femtosecond laser settings on clinical outcomes and ultrastructural analysis of the lenticule surface in small incision lenticule extraction (SMILE). METHODS: A total of 78 eyes from 39 consecutive patients were included with the standard scanning mode (energy level of 105 nJ vs spot distance of 3 mm) in one eye and the fast scanning mode (energy level of 110 nJ vs spot distance of 4.5 mm) in the other eye, all eyes being randomly assigned. Patients received complete ophthalmic examinations preoperatively and at different follow-up visits after SMILE. Ten human corneal lenticules were analyzed using scanning electron microscopy. RESULTS: Uncorrected distance visual acuity at 1 day and 1 week postoperatively was -0.06 ± 0.10 and -0.11 ± 0.05 logMAR, respectively, in the fast scanning group, which was significantly better than in the standard scanning group (-0.11 ± 0.08 and -0.12 ± 0.05 logMAR, respectively), and no significant difference was found between the groups at 1 and 3 months. The contrast sensitivity was higher at different time points in the fast scanning mode group compared with the standard scanning group (all P < .05). Ultrastructurally, the corneal lenticules from the fast scanning group showed a smoother surface than those from the standard scanning mode group qualitatively and quantitatively (all P < .001). CONCLUSIONS: SMILE using the fast scanning mode facilitates better visual acuity with improved contrast sensitivity in the early postoperative period. Experimental studies on the ultrastructure of corneal lenticules support these clinical results. [J Refract Surg. 2020;36(1):34-41.].

Screening Candidates for Refractive Surgery With Corneal Tomographic-Based Deep Learning.

Importance: Evaluating corneal morphologic characteristics with corneal tomographic scans before refractive surgery is necessary to exclude patients with at-risk corneas and keratoconus. In previous studies, researchers performed screening with machine learning methods based on specific corneal parameters. To date, a deep learning algorithm has not been used in combination with corneal tomographic scans. Objective: To examine the use of a deep learning model in the screening of candidates for refractive surgery. Design, Setting, and Participants: A diagnostic, cross-sectional study was conducted at the Zhongshan Ophthalmic Center, Guangzhou, China, with examination dates extending from July 18, 2016, to March 29, 2019. The investigation was performed from July 2, 2018, to June 28, 2019. Participants included 1385 patients; 6465 corneal tomographic images were used to generate the artificial intelligence (AI) model. The Pentacam HR system was used for data collection. Interventions: The deidentified images were analyzed by ophthalmologists and the AI model. Main Outcomes and Measures: The performance of the AI classification system. Results: A classification system centered on the AI model Pentacam InceptionResNetV2 Screening System (PIRSS) was developed for screening potential candidates for refractive surgery. The model achieved an overall detection accuracy of 94.7% (95% CI, 93.3%-95.8%) on the validation data set. Moreover, on the independent test data set, the PIRSS model achieved an overall detection accuracy of 95% (95% CI, 88.8%-97.8%), which was comparable with that of senior ophthalmologists who are refractive surgeons (92.8%; 95% CI, 91.2%-94.4%) (P = .72). In distinguishing corneas with contraindications for refractive surgery, the PIRSS model performed better than the classifiers (95% vs 81%; P < .001) in the Pentacam HR system on an Asian patient database. Conclusions and Relevance: PIRSS appears to be useful in classifying images to provide corneal information and preliminarily identify at-risk corneas. PIRSS may provide guidance to refractive surgeons in screening candidates for refractive surgery as well as for generalized clinical application for Asian patients, but its use needs to be confirmed in other populations.

15-Month Visual Outcomes and Corneal Power Changes of SMILE in Treating High Myopia With Maximum Myopic Meridian Exceeding 10.00 D.

PURPOSE: To evaluate the long-term visual and refractive outcomes, optical quality, and stability of the cornea and axial length after small incision lenticule extraction (SMILE) for the correction of high myopia with a maximum myopic meridian exceeding 10.00 diopters (D). METHODS: Via a prospective cohort study, 53 eyes (53 patients) with a maximum myopic meridian exceeding 10.00 D were corrected with a VisuMax femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany) at the Zhongshan Ophthalmic Center of Sun Yat-sen University. Refractive outcomes, aberrations, axial length, and corneal curvature were evaluated preoperatively and at 1, 3, and 15 months postoperatively. RESULTS: At 15 months postoperatively, the efficacy and safety indexes were 0.91 ± 0.25 and 1.15 ± 0.18, respectively. A total of 72% of eyes were within ±0.50 D and 89% were within ±1.00 D of the attempted spherical equivalent, respectively. From 1 to 15 months postoperatively, the significant regression was -0.24 ± 0.28 D (P < .001) on manifest refraction and -0.43 ± 0.54 D (P < .001) on anterior corneal curvature. In addition, a significant increase of 0.20 µm (P = .016) was observed in the spherical aberration. No significant change was observed in posterior corneal curvature (P > .999), including mean keratometry or astigmatism, or in the ocular axis length from 1 to 15 months postoperatively (26.82 ± 0.93 and 26.82 ± 0.95 mm, respectively, P > .99). CONCLUSIONS: SMILE had long-term safety, efficacy, and predictability when treating high myopia with a maximum myopic meridian exceeding 10.00 D. Both a manifest refraction regression of -0.24 D and a significant spherical aberration increase of 0.20 µm were observed between 1 and 15 months postoperatively, due to the increased anterior corneal curvature. [J Refract Surg. 2019;35(1):31-39.].

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

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

Effect of Cyclotorsion Compensation With a Novel Technique in Small Incision Lenticule Extraction Surgery for the Correction of Myopic Astigmatism.

PURPOSE: To comparatively investigate the clinical outcomes of small incision lenticule extraction (SMILE) surgery with or without cyclotorsion compensation for the correction of myopic astigmatism. METHODS: This prospective, double-blinded, randomized controlled trial included patients who underwent SMILE surgery with bilateral myopic astigmatism. Two eyes of a single patient were randomly divided into the static cyclotorsion compensation (SCC) group and the control group. In the SCC group, the intraoperative cyclotorsion was manually compensated with a novel technique. In the control group, the cyclotorsion was not compensated. Visual acuity, manifest refraction, aberrations, objective visual quality, and contrast sensitivity were measured preoperatively and postoperatively. RESULTS: A total of 132 eyes from 66 patients were analyzed at the 3-month follow-up. The mean preoperative cylinder values in the SCC and control groups were -1.52 ± 0.81 and -1.57 ± 0.82 diopters (D), respectively. The mean cyclotorsion during surgery was 0.60° ± 0.63° (range: 0° to 3.2°) in the SCC group and 3.21° ± 2.33° (range: 0.1° to 10.8°) in the control group (P < .001). Both groups showed favorable results in the correction of myopic astigmatism. No statistically significant difference was found between the two groups in visual and refractive outcomes, vector parameters, entire eye aberrations, objective visual quality, or contrast sensitivity. No significant benefit was gained from cyclotorsion compensation, even in the high astigmatism subgroup. CONCLUSIONS: The cyclotorsion compensation technique used in this study helped minimize the alignment error but was not compulsory because the ocular rotation in SMILE surgery using a well-controlled position was too small to affect the astigmatic outcomes or postoperative visual quality. [J Refract Surg. 2019;35(5):301-308.].

Development of the Modified Lenticule Edge Dissection Technique for Small Incision Lenticule Extraction.

PURPOSE: To identify and develop an efficient technique to separate the lenticule edge in small incision lenticule extraction (SMILE). METHODS: Four hundred eyes of 400 consecutive patients with myopia assigned to receive SMILE were included in the study. Eyes with poor-quality laser treatment were excluded, and the second eye of the same patient was included. Two skilled surgeons performed SMILE in the Zhongshan Ophthalmic Center. Each surgeon was allotted 200 patients. One surgeon used the modified technique, whereas the other surgeon used the conventional technique to identify and separate the lenticule edge. All intraoperative complications associated with lenticule edge dissection and the duration of lenticule dissection were recorded. RESULTS: There were 200 eyes each in the modified technique group (group A) and the conventional technique group (group B). The mean lenticule dissection time was 49 ± 10 seconds in group A and 59 ± 43 seconds in group B (P = 0.002). Within 70 seconds, lenticule dissection was completely finished in 96.5% of eyes in group A and 86.0% in group B. Difficult lenticule dissection was experienced in 3.5% (7/200) of cases in group A and in 14.0% (28/200) of cases in group B. CONCLUSIONS: The modified lenticule edge dissection technique of SMILE is simpler and faster in identifying the correct dissection plane. It is efficient in reducing surgical manipulation, shortening the learning curve required for lenticule dissection, and allows surgeons to perform SMILE more safely and efficiently.

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.

Investigation of iron spin crossover pressure in Fe-bearing MgO using hybrid functional.

Pressure-induced spin crossover behaviors of Fe-bearing MgO were widely investigated by using an LDA + U functional for describing the strongly correlated Fe-O bonding. Moreover, the simulated spin crossover pressures depend on the applied U values, which are sensitive to environments and parameters. In this work, the spin crossover pressures of (Mg1-x ,Fe x )O are investigated by using the hybrid functional with a uniform parameter. Our results indicate that the spin crossover pressures increase with increasing iron concentration. For example, the spin crossover pressure of (Mg0.03125,Fe0.96875)O and FeO was 56 GPa and 127 GPa, respectively. The calculated crossover pressures agreed well with the experimental observations. Therefore, the hybrid functional should be an effective method for describing the pressure-induced spin crossover behaviors in transition metal oxides.

Evaluation of Human Corneal Lenticule Quality After SMILE With Different Cap Thicknesses Using Scanning Electron Microscopy.

PURPOSE: To evaluate the surface characteristics of lenticules created by small-incision lenticule extraction (SMILE) with different cap thicknesses. METHODS: This prospective study included 20 consecutive patients who underwent bilateral SMILE. Surface regularity of the extracted corneal lenticule was analyzed using scanning electron microscopy (SEM) combined with 2 methods: qualitative and quantitative regularity. Qualitative regularity of SEM images was graded by masked observers using an established scoring system. Quantitative regularity of SEM images was assessed by counting the total number and areas of tissue bridges using Image-Pro Plus software. Four different cap thickness of 120, 130, 140, and 150 µm were compared. Refractive outcomes of patients were measured at baseline and 1 month after surgery. RESULTS: As 10 specimens were not analyzable, only 30 eyes were included. Postoperatively, all eyes had postoperative uncorrected distance visual acuity of 20/20 or better; 43% had an unchanged corrected distance visual acuity; 43% gained 1 line; 10% lost 1 line. Ultrastructurally, surface irregularity was primarily caused by tissue bridges. The average surface regularity score obtained was 10.87 ± 2.40 for 120 µm, 10.78 ± 2.60 for 130 µm, 8.76 ± 2.16 for 140 µm, and 8.70 ± 2.66 for 150 µm (P < 0.001). The total number and areas of tissue bridges of 120 to 130 µm were significantly less than 140 to 150 µm (P < 0.05). Surface regularity decreased as cap thickness increased (P < 0.05). CONCLUSIONS: There is smoother appearance of the lenticular surface as seen through SEM when a thin cap is created compared with a thick cap qualitatively and quantitatively.