Three-year results of central corneal stromal thickness reduction in small-incision lenticule extraction for high myopia correction.

BACKGROUND: To investigate the long-term corneal stromal remodeling and central stromal thickness (CST) reduction accuracy after small-incision lenticule extraction (SMILE) for high myopia correction. METHODS: This prospective study included 30 patients (50 eyes) who had undergone SMILE. Measurements of CST reduction using optical coherence tomography were performed at 1 month, 6 months, 1 year, and 3 years after surgery. Correlations were performed between planned and achieved CST reductions. RESULTS: The study enrolled 50 eyes of 30 patients. The mean spherical equivalent was -9.25±1.52 D(diopters). The postoperative CST increased in the first month after surgery and remained stable for a year. Thereafter, it remained stable during follow-up from 1 to 3 years postoperatively. The predicted CST reduction was 146.4±10.3 µm. The achieved CST reductions at 1 month, 6 months, 1 year, and 3 years after surgery were 135.3±12.1 µm, 130.8±10.6 µm, 125.9±9.4 µm, and 122.2±10.6 µm, respectively. An overestimation of CST reduction was observed three years after surgery. Correlation analysis revealed a strong correlation between planned and achieved CST reductions; however, no correlation was found between CST reductions predicted error and the planned CST reductions. CONCLUSION: During long-term follow-up, our findings revealed a significant stromal remodeling following SMILE in patients with high myopia. Therefore, clinicians should consider it when screening patients with high myopia for SMILE.

Correlation between mental status and prevalence of asthenopia in Chinese college students.

BACKGROUND: The purpose of this study was to identify the possible association between mental status and the risk of self-reported asthenopia among college students in China. METHODS: Ten thousand students were randomly assessed in the study using a self-reported asthenopia questionnaire. Their demographic characteristics and mental status were recorded. Univariate analysis was performed to preliminarily select potential risk and protective factors. Then, multivariate logistic regression was used to estimate odds ratios for the selected risk factors of interest. RESULTS: Among the 8370 students who completed the survey, the prevalence of asthenopia was 61.0%. Multivariate analysis revealed a significant relationship between asthenopia and depressive symptoms (OR 1.511 95% CI: 1.350-1.691), obsessive-compulsive symptoms (OR 1.477, 95% CI: 1.338-1.632), gender and study load. The place college students spent their off-hours (OR 0.841, 95% CI: 0.784-0.902) was found to be the strongest factor for decreasing the occurrence of asthenopia complaints. CONCLUSION: Asthenopia appears common in Chinese college students. In addition to depressive symptoms, we should pay attention to obsessive-compulsive symptoms when considering means of preventing asthenopia. Harmonious social relationships, outdoor off-hour activities and exercising more than three times per week are crucial to relieving visual fatigue. Further study is still needed in this area.

Exploration of the pathophysiology of high myopia via proteomic profiling of human corneal stromal lenticules.

This study aimed to investigate the underlying pathophysiology of high myopia by analyzing the proteome of human corneal stromal lenticule samples obtained through small incision lenticule extraction (SMILE). A total of thirty-two patients who underwent SMILE were included in the study. Label-free quantitative proteomic analysis was performed on corneal stromal lenticule samples, equally representing high myopia (n = 10) and low myopia (n = 10) groups. The identified and profiled lenticule proteomes were analyzed using in silico tools to explore biological characteristics of differentially expressed proteins (DEPs). Additionally, LASSO regression and random forest model were employed to identify key proteins associated with the pathophysiology of high myopia. The DEPs were found to be closely linked to immune activation, extracellular matrix, and cell adhesion-related pathways according to gene ontology analysis. Specifically, decreased expression of COL1A1 and increased expression of CDH11 were associated with the pathogenesis of high myopia and validated by western blotting (n = 6) and quantitative real time polymerase chain reaction (n = 6). Overall, this study provides evidence that COL1A1 and CDH11 may contribute to the pathophysiology of high myopia based on comparative proteomic profiling of human corneal stromal lenticules obtained through SMILE.

Effective Optical Zone and Centration Following SMILE and FS-LASIK for High Myopia Calculated With a Novel Method.

PURPOSE: To compare the effective optical zone (EOZ) and centration in eyes with high myopia after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) using a novel method. METHODS: Forty eyes of 40 consecutive patients with high myopia scheduled for SMILE or FS-LASIK were enrolled in the study. The EOZ, optical zone decentration, and corneal aberrations were analyzed using Scheimpflug imaging. These values were then analyzed and compared between the two procedures 6 months after surgery. RESULTS: The mean EOZ diameter for SMILE (4.41 ± 0.14 mm) was larger than that for FS-LASIK (4.24 ± 0.28 mm; P = .002), corresponding to reductions of 1.60 ± 0.11 and 1.71 ± 0.21 mm, respectively, compared with the programmed optical zone (POZ) (P = .007). Moreover, the total decentration for SMILE (0.33 ± 0.12 mm) was greater than that for FS-LASIK (0.27 ± 0.15 mm; P = .020). The induction of spherical aberration (SA) was lower with SMILE than with FS-LASIK (P = .007). CONCLUSIONS: A larger EOZ and less SA were observed after SMILE than after FS-LASIK in eyes with high myopia. [J Refract Surg. 2023;39(11):736-740.].

LncRNA-XR_002792574.1-mediated ceRNA network reveals potential biomarkers in myopia-induced retinal ganglion cell damage.

BACKGROUND: Long noncoding RNAs (lncRNAs) play a key role in the occurrence and progression of myopia. However, the function of lncRNAs in retinal ganglion cells (RGCs) in the pathogenesis of myopia is still unknown. The aim of our study was to explore the lncRNA-mediated competing endogenous RNA (ceRNA) network in RGCs during the development of myopia. METHODS: RNA sequencing was performed to analyze lncRNA and mRNA expression profiles in RGCs between guinea pigs with form-deprived myopia (FDM) and normal control guinea pigs, and related ceRNA networks were constructed. Then, potentially important genes in ceRNA networks were verified by qRT‒PCR, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to explore biological functions in the RGCs of FDM guinea pigs. The important genes and related signaling pathways were further verified by qRT‒PCR, immunohistochemistry, immunofluorescence and Western blot in myopia in FDM guinea pigs, FDM mice, and highly myopic adults. RESULTS: The distribution of RGCs was uneven, the number of RGCs was decreased, and RGC apoptosis was increased in FDM guinea pigs. In total, 873 lncRNAs and 2480 mRNAs were determined to be differentially expressed genes in RGCs from normal control and FDM guinea pigs. Via lncRNA-mediated ceRNA network construction and PCR verification, we found that lncRNA-XR_002792574.1 may be involved in the development of myopia through the miR-760-3p/Adcy1 pathway in RGCs. Further verification in FDM guinea pigs, FDM mice, and highly myopic adults demonstrated that the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis in RGCs might be related to cGMP/PKG, the apelin signaling pathway and scleral remodeling. CONCLUSION: We demonstrated that the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis in RGCs might be related to myopia. On the one hand, the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis might inhibit the cGMP/PKG and apelin signaling pathways in RGCs, thereby causing RGC damage in myopia. On the other hand, the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis may cause myopic scleral remodeling through the ERK-MMP-2 pathway. These findings may reveal novel potential targets in myopia and provide reference value for exploration and development of gene editing therapeutics for hereditary myopia.

Lenticule Intrastromal Keratoplasty for the Correction of Iatrogenic High Hyperopia.

PURPOSE: The aim of this study was to evaluate the safety, efficacy, and predictability of lenticule intrastromal keratoplasty (LIKE) for the correction of iatrogenic high hyperopia. METHODS: Three patients (4 eyes) were referred to our department because of overcorrection of myopia induced by femtosecond laser-assisted in situ keratomileusis. All eyes exhibited hyperopia (between +4.00 and +8.00 D) and thin corneas ranging from 307 to 378 µm. Because of the regression of the use of laser ablation to correct high hyperopia and thin corneas, we initially adopted LIKE to correct iatrogenic high hyperopia in all 4 eyes. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, and anterior segment optical coherence tomography findings were recorded during each follow-up evaluation. RESULTS: No postoperative complications, such as interface haze and opacification, were observed in the 4 eyes during each follow-up evaluation, with an average follow-up of 9.50 months. All eyes had significantly improved UDVA postoperatively. A total of 3 eyes achieved an UDVA of 20/25 or better while the other 1 eye had an UDVA of 20/40 postoperatively. In addition, 2 of the 4 eyes had a postoperative UDVA equal to or better than preoperative CDVA. No eyes lost any CDVA lines. All 4 eyes were within ±0.50 D of the spherical power (intended target of 0). The central corneal thickness and curvature of the anterior corneal surface in all 4 eyes increased postoperatively. Anterior segment optical coherence tomography revealed that the lenticule was transparent, with no wrinkles or offsets, during each follow-up evaluation. CONCLUSIONS: LIKE for the correction of iatrogenic hyperopia has good efficacy and safety. Although an extremely thin cornea after overcorrection may not be suitable for hyperopic laser enhancement, LIKE is a good choice because of its good predictability and ability to restore the normal corneal structure.

Effects of microplastics on the properties of different types of sewage sludge and strategies to overcome the inhibition: A review.

Microplastics have been identified as an emerging pollutant. When microplastics enter wastewater treatment plants, the plant traps most of the microplastics in the sludge during sewage treatment. Therefore, the effects of microplastics on sludge removal performance, and on the physical and chemical properties and microbial communities in sludge, have attracted extensive attention. This review mainly describes the presence of microplastics in wastewater treatment plants, and the effects of microplastics on the decontamination efficiency and physicochemical properties of activated sludge, aerobic granular sludge, anaerobic granular sludge and anaerobic ammonium oxidation sludge. Further, the review summarizes the effects of microplastics on microbial activity and microbial community dynamics in various sludges in terms of type, concentration, and contact time. The mechanisms used to strengthen the reduction of microplastics, such as biochar and hydrochar, are also discussed. This review summarizes the mechanism by which microplastics influence the performance of different types of sludge, and proposes effective strategies to mitigate the inhibitive effect of microplastics on sludge and discusses removal technologies of microplastics in sewage. Biochar and hydrochar are one of the effective measures to overcome the inhibition of microplastics on sludge. Meanwhile, constructed wetland may be one of the important choice for the future removal of microplastics from sewage. The goal is to provide theoretical support and insights for ensuring the stable operation of wastewater treatment plants and reducing the impact of microplastics on the environment.

Efficacy Comparison Between Toric Posterior Chamber Phakic IOL and Posterior Chamber Phakic IOL Plus Modified Steep Meridian Corneal Relaxing Incision for Moderate to High Astigmatism Corrections.

PURPOSE: To compare posterior chamber phakic intraocular lens (Implantable Collamer Lens [STAAR Surgical]) (ICL) plus modified steep meridian corneal relaxing incision (MS-CRI) to toric posterior chamber phakic intraocular lens (Toric Implantable Collamer Lens [STAAR Surgical]) (TICL) implantation for the correction of moderate to high astigmatism. METHODS: In this prospective, randomized clinical trial, patients with myopia who had moderate to high astigmatism (200 eyes) were enrolled and divided into TICL (n = 100) and MSCRI (n = 100) groups. All patients underwent examinations for uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and subjective refraction before surgery and at the 1- and 6-month follow-up visits. Vector astigmatism analysis was evaluated using the Alpins method. RESULTS: The mean UDVA and CDVA demonstrated significant improvement after surgery in both groups. During the 6-month follow-up, the MS-CRI group showed a slight regression tendency (P < .001) and the TICL group was stable for the astigmatism correction (P = .510). At 6 months postoperatively, the mean magnitudes of the surgically induced astigmatism were 1.46 ± 0.53 and 1.10 ± 0.48 diopters (P < .001). The correction index of the TICL group was closer to 1 compared to that of the MS-CRI group (0.95 vs 0.76). Approximately 99% of eyes in the TICL group had angle of error within ±15°, whereas 89% eyes in the MS-CRI group were within that range. A significant relationship between the magnitudes of target induced astigmatism and correction index was noted in the MS-CRI group (P < .001), but not in the TICL group (P = .592). CONCLUSIONS: TICL implantation could achieve better visual outcomes for correcting moderate to high astigmatism compared to ICL implantation plus MS-CRI. [J Refract Surg. 2023;39(8):539-545.].

Pharmacological Accommodative Changes of the Anterior Segment and Its Impact on the Vault in Implantable Collamer Lens Implantation.

PURPOSE: To estimate the accommodative changes of the anterior segment and its impact on the central and peripheral vaults after Visian Implantable Collamer Lens (ICL) (STAAR Surgical) implantation. METHODS: Eighty eyes of 40 consecutive patients (mean age: 28.05 years; range: 19 to 42 years) were examined 3 months after ICL implantation. Eyes were randomly divided into a mydriasis group and a miosis group. Anterior chamber depth (ACD) to crystalline lens (ACD-L), anterior chamber depth to ICL (ACD-ICL), central distance from endothelium to sulcus to sulcus (ASL), central distance from sulcus to sulcus to crystalline lens (STS-L), central distance from ICL to sulcus to sulcus (STS-ICL), and central (cICL-L), midperipheral (mICL-L), and peripheral (pICL-L) vaults were measured by ultrasound biomicroscopy at baseline and after induction with tropicamide or pilocarpine. RESULTS: After tropicamide treatment, cICL-L, mICL-L, and pICL-L decreased from 0.531 ± 0.200, 0.419 ± 0.173, and 0.362 ± 0.150 mm to 0.488 ± 0.171, 0.373 ± 0.153, and 0.311 ± 0.131 mm, respectively. The values decreased from 0.540 ± 0.185, 0.445 ± 0.172, and 0.388 ± 0.149 mm to 0.464 ± 0.199, 0.378 ± 0.156, and 0.324 ± 0.137 mm after pilocarpine administration, respectively. The ASL and STS showed a significant increase in the mydriasis group (all P ≤ .038), but a decrease in the miosis group (all P < .001). The ACD-L increased and STS-L decreased in the mydriasis group (all P < .001), indicating the backward shift of the crystalline lens, whereas crystalline lens forward shift was observed in the miosis group. Additionally, the STS-ICL decreased in both groups (all P ≤ .021), suggesting the ICL backward shift. CONCLUSIONS: Both central and peripheral vaults decreased during the pharmacological accommodation process, and the ciliaris-iris-lens complex contributed to the changes. [J Refract Surg. 2023;39(6):414-420.].

Effects of upward flow rate and modified biochar location on the performance and microecology of an anaerobic reactor treating kitchen waste.

Increasing the value of food waste through anaerobic digestion is an attractive strategy. Meanwhile, the anaerobic digestion of kitchen waste also faces some technical challenges. In this study, four EGSB reactors were equipped with Fe-Mg-chitosan bagasse biochar at different locations, and the reflux pump flow rate was increased to change the upward flow rate of the reactor. The effects of adding modified biochar at different locations under different upward flow rate on the efficacy and microecology of anaerobic reactors treating kitchen waste were investigated. Results showed that Chloroflexi was the dominant microorganism when the modified biochar was added to the lower, middle, and upper parts of the reactor and mixed in the reactor, accounting for 54%, 56%, 58%, and 47%, respectively, on day 45. With the increased upward flow rate, the abundance of Bacteroidetes and Chloroflexi increased, while Proteobacteria and Firmicutes decreased. It was worth noting that the best COD removal effect was achieved when the anaerobic reactor upward flow rate was v2 = 0.6 m/h and the modified biochar was added in the upper part of the reactor, during which the average COD removal rate reached 96%. In addition, mixing modified biochar throughout the reactor while increasing the upward flow rate provided the greatest stimulus for the secretion of tryptophan and aromatic proteins in the sludge extracellular polymeric substances. The results provided a certain technical reference for improving the efficiency of anaerobic digestion of kitchen waste and scientific support for the application of modified biochar to the anaerobic digestion process.

Visual outcomes and corneal densitometry after allogenic and autologous lenticule intrastromal keratoplasty for the correction of moderate-to-high hyperopia.

AIM: This study aimed to evaluate the visual outcomes and corneal densitometry (CD) after allogenic lenticule intrastromal keratoplasty (AL-LIKE) and autologous lenticule intrastromal keratoplasty (AU-LIKE) for the correction of moderate-to-high hyperopia. METHODS: Ten subjects (14 eyes) underwent AL-LIKE and eight (8 eyes) underwent AU-LIKE. Patients were examined preoperatively and 1 day, 1 month, and 6 months postoperatively. The visual outcomes and CD for both surgical methods were evaluated. RESULTS: No postoperative complications were observed with either method. The efficacy index was 0.85±0.18 and 0.90±0.33 in the AL-LIKE and AU-LIKE groups, respectively. The safety indices were 1.07±0.21 and 1.25±0.37 in the AL-LIKE and AU-LIKE groups, respectively. The CD values of the anterior, central, and posterior layers in the AL-LIKE group increased significantly at 1 day postoperatively (all P < 0.05). The CD values of the anterior and central layers remained significantly higher than the preoperative values at 6 months postoperatively (all P < 0.05). The CD values of the anterior layer in the AU-LIKE group increased significantly 1 day postoperatively (all P < 0.05) and decreased to preoperative values (all P > 0.05) 1 month postoperatively. CONCLUSION: Both AL-LIKE and AU-LIKE exhibit good efficacy and safety in correcting hyperopia. However, AU-LIKE may have a smaller affected area and faster recovery time than those associated with AU-LIKE related to changes in corneal transparency.

Comparison of Visual Outcomes and Higher-order Aberrations Between FS-LASIK and SMI-LIKE for Moderate to High Hyperopia: A 2-Year Result.

PURPOSE: The aim of the study was to evaluate and compare the long-term visual outcomes and higher-order aberrations (HOAs) between femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule intrastromal keratoplasty (SMI-LIKE) in the correction of moderate to high hyperopia. METHODS: In this study, 16 subjects (20 eyes) underwent FS-LASIK and 7 subjects (10 eyes) underwent SMI-LIKE. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, mean keratometry (Km), anterior asphericity (Q), and HOAs preoperatively and 2 years postoperatively were obtained in both procedures. RESULTS: The efficacy indices of the FS-LASIK group and the SMI-LIKE group were 0.85 ± 0.14 and 0.87 ± 0.17, respectively. The safety indices of the FS-LASIK and SMI-LIKE groups were 0.99 ± 0.15 and 1.08 ± 0.24, respectively. No significant difference in safety index or efficacy index was found between the FS-LASIK and SMI-LIKE groups (all P > 0.05). The correlation coefficient of the attempted versus achieved spherical equivalent postoperatively was 0.69 ( P < 0.01) and 0.89 ( P < 0.01) in the FS-LASIK group and SMI-LIKE groups, respectively. The front Km, negative Q value, negative spherical aberrations (SAs), coma, and total HOAs significantly increased postoperatively in the 2 groups ( P < 0.05). The FS-LASIK group had greater changes in Q value and SA postoperatively than the SMI-LIKE group ( P < 0.01). CONCLUSIONS: SMI-LIKE had similar safety and efficacy to FS-LASIK in the correction of moderate to high hyperopia. However, SMI-LIKE may equip better visual quality postoperatively for its lower Q value and SA changes than FS-LASIK.

Efficacy Comparison Between Steep-Meridian Incision and Non-Steep-Meridian Incision in Implantable Collamer Lens Surgery with Low-to-Moderate Astigmatism.

INTRODUCTION: To compare the visual outcomes of astigmatism correction with implantable collamer lens (ICL) surgery with low-to-moderate astigmatism through a steep-meridian corneal relaxing incision (SM-CRI) and non-steep-meridian corneal relaxing incision (NSM-CRI). METHODS: Seventy eyes of 70 patients with myopia and myopic astigmatism who underwent ICL V4c implantation were classified into two groups: SM-CRI and NSM-CRI. Refractive outcomes and vector analysis were evaluated preoperatively and 6 months postoperatively. RESULTS: At the postoperative 6 month visit, all participants in both groups achieved an uncorrected distance visual acuity (UDVA) of 20/20 or better. The difference vector (DV) showed that the residual astigmatism in the SM-CRI group was much smaller than that in the NSM-CRI group (P = 0.021), and the correction index (CI) was 0.84 ± 0.30 and 0.67 ± 0.35 for the SM-CRI and NSM-CRI groups, respectively, with a significant statistical difference (P = 0.013). Approximately 71% of eyes in the SM-CRI group had an angle of error (AE) within ± 15°, whereas 55% of eyes in the NSM-CRI group were within that range. The absolute mean AE was 10.13 ± 14.57° in the SM-CRI group, compared with 23.88 ± 28.22° in the NSM-CRI group (P = 0.038). CONCLUSION: SM-CRI can alleviate corneal astigmatism and decrease the cylindrical diopter of the ICL, thus improving postoperative visual quality compared with NSM-CRI.

Changes in the posterior corneal surface after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) performed into a pocket (SMI-LIKE) or under a flap (FS-LIKE).

BACKGROUND: To compare the changes in posterior corneal surface after small-incision lenticule intrastromal keratoplasty (SMI-LIKE) and femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) for hyperopia correction. METHODS: In this prospective comparative randomized study, 23 eyes with hyperopia were recruited. Eyes were categorized into two groups-SMI-LIKE group (11 eyes) and FS-LIKE group (12 eyes). Lenticules from myopia small incision lenticule extraction were implanted into a pocket (SMI-LIKE group) or at a depth of 100 µm under a flap (FS-LIKE group). Posterior corneal elevations in the center, mid-periphery, and periphery, as well as mean keratometry of the posterior corneal surface (Kmb) were measured using a Pentacam over a three-month follow-up. RESULTS: All surgeries were completed successfully and no complications occurred. At one day postoperatively, there was a slight backward change with SMI-LIKE and a forward change with FS-LIKE in the central region of the posterior corneal elevation. Conversely, the peripheral area showed forward displacement in SMI-LIKE and an apparent backward change in FS-LIKE. The mid-peripheral regions manifested a backward change after the procedure throughout the entire follow-up in both groups. Kmb exhibited flattening at one month postoperatively and subsequently returned to its original level at three months after SMI-LIKE while in FS-LIKE, Kmb steepened after lenticule implantation with a significant change noted at one day postoperatively (P = 0.001). CONCLUSIONS: Posterior corneal surface after SMI-LIKE and FS-LIKE exhibited different change patterns in various corneal regions, with the most prominent change occurring at one day postoperatively during the three-month follow-up. TRIAL REGISTRATION: Chinese Clinical Trial Registry: ChiCTR-ONC-16008300. Registered on Apr 18th, 2016.  http://www.chictr.org.cn/edit.aspx?pid=14090&htm=4.

Correlation between the ablation ratio and posterior corneal stability after small incision lenticule extraction for high myopia.

PURPOSE: The aim of this study is to investigate changes in posterior corneal elevation and their correlations with the ablation ratio 3 years after small incision lenticule extraction (SMILE) for high myopia. METHODS: Eighty eyes underwent SMILE were enrolled in this study. Eyes were classified into two groups based on the ablation ratio (AR, lenticule thickness from SMILE machine/thinnest corneal thickness): group A (< 25%, 40 eyes) and group B (≥ 25%, 40 eyes). Pentacam was used to measure the posterior corneal elevation at the central point, thinnest point, and posterior maximum elevation (PME) and the mean posterior elevation in the central 2-mm area (MPE-2 mm), 4-mm area, and 6-mm area at the 3-year follow-up. RESULTS: More than 85% of the eyes had an AR of less than 27%, and no cases of iatrogenic keratectasia developed. In both groups, for central region, posterior elevation decreased implying backward displacement; for peripheral region, it increased indicating forward trend. There was no significant difference in changes in all determined parameters between the two groups (P ≥ 0.07). Moreover, no significant correlation was noted between AR and posterior elevation changes. In group A, decreasing changes in PME (r = - 0.42, P = 0.01) and MPE-2 mm (r = 0.40, P = 0.01) demonstrated negative correlations with residual bed thickness. CONCLUSION: Region-dependent changes were demonstrated in the eyes that underwent SMILE. The central area showed a subtly declining posterior elevation, and the peripheral area showed a slightly increasing elevation. The limited ablation ratio had no impact on the changes in posterior corneal elevation.

Comparison of Predictability in Central Corneal Thickness Reduction After SMILE and FS-LASIK for High Myopia Correction.

INTRODUCTION: To compare central corneal thickness (CCT) reduction after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in eyes with high myopia. METHODS: In this prospective, consecutive study, 70 eyes with high myopia undergoing SMILE (n = 35) or FS-LASIK (n = 35) were recruited. Corneal topography images were acquired using the Pentacam HR imaging system preoperatively and at 1 day, 1 month, and 6 months postoperatively. Predicted CCT reduction was extracted directly from the VisuMax femtosecond laser system or MEL 80 excimer laser platform. The achieved CCT reduction was determined using corneal thickness difference maps from the Pentacam. Comparative statistics and linear regression analyses were performed to evaluate the predictability in stromal thickness reduction. RESULTS: The mean predicted CCT reductions were 152.9 ± 6.7 µm and 150.9 ± 7.3 µm in the FS-LASIK and SMILE groups, respectively, with no statistical difference. For each follow-up time, no significant difference was noted in the two groups in the achieved CCT reduction. At 6-month follow-up, the CCT reductions were overestimated to be 23.06 ± 6.97 µm and 28.29 ± 13.92 µm in the SMILE and FS-LASIK groups, respectively (P = 0.003), showing statistical difference. Regression analysis revealed that the positive correlation between achieved and predicted CCT reductions was stronger in SMILE (R2 = 0.5065, P < 0.001) than in FS-LASIK (R2 = 0.2237, P = 0.004). Overestimated CCT reduction was not correlated with predicted CCT reduction in either group. CONCLUSIONS: Systematically overestimated CCT reduction is found after SMILE and FS-LASIK in high myopia correction. Deviations between planned and achieved CCT reductions are more pronounced in FS-LASIK than in SMILE.

Achieved Lenticule Diameter and Functional Optical Zone in Hyperopic Eyes After Lenticule Intrastromal Keratoplasty.

PURPOSE: To investigate achieved lenticule diameter (ALD) and functional optical zone (FOZ) following femtosecond laser-assisted lenticule intrastromal keratoplasty (FS-LIKE) or small incision lenticule intrastromal keratoplasty (SMI-LIKE). METHODS: Small incision lenticule extraction (SMILE)-derived human lenticules were placed on the surface of a contact glass (CG) and model eye (ME). Ex vivo ALDs were assessed at different hydration times. The ALD and FOZ were obtained using optical coherence tomography and Scheimpflug tomography at 6 months after lenticule implantation. RESULTS: At 1 hour after hydration, lenticules achieved a slightly larger CG-loading ALD (6.63 ± 0.07 mm) and similar ME-loading ALD (6.53 ± 0.07 mm) as compared to a programmed optical zone (POZ) of 6.5 mm (P < .001). At 6 months after surgery, FS-LIKE with a POZ of 6.5 mm obtained an ALD of 6.20 ± 0.21 mm, which was larger than SMI-LIKE with a POZ of 6.64 mm (5.90 ± 0.14 mm, P = .001). The mean FOZ diameters were 5.33 ± 0.28 and 5.11 ± 0.14 mm for the FS-LIKE and SMI-LIKE groups, respectively (P = .022). The absence of significant differences in the ALD and FOZ among the different meridians indicated that the achieved lenticule and optical zone shapes were circular. CONCLUSIONS: An accurate lenticular size could be obtained from SMILE, and FS-LIKE could achieve a larger FOZ than SMI-LIKE, attributed to attaining a larger ALD. [J Refract Surg. 2022;38(12):791-796.].

Effect of keratometric astigmatism on visual outcomes following small incision lenticule extraction.

Purpose: To investigate the influence of keratometric astigmatism on visual outcomes following small incision lenticule extraction (SMILE). Methods: Eighty eyes undergoing SMILE for myopia correction were classified into two groups based on preoperative keratometric astigmatism: low keratometric astigmatism (LA) and high keratometric astigmatism (HA) groups. Refractive outcomes, vector components, and changes in higher order aberrations (HOAs) were evaluated preoperatively and 6 months postoperatively. Results: At the postoperative 6-month visit, no significant difference was observed in the decentered distance between the HA and LA groups (HA: 0.17 ± 0.08 mm, LA: 0.16 ± 0.08 mm, P = 0.189). No significant differences in the correction index (P = 0.481), absolute angle of error (P = 0.104), or index of success (P = 0.147) were observed between the two groups. There was no significant difference in the induction of corneal aberrations between the two groups. Furthermore, there were no significant associations between the decentered distance and the vector components of astigmatic correction or induction of higher-order aberration in the HA group (P ≥ 0.294, P ≥ 0.112) or the LA group (P ≥ 0.323, P ≥ 0.080). Conclusions: SMILE for high keratometric astigmatism could achieve comparable treatment centration and visual quality to that of low keratometric astigmatism.

Comparison of the Functional Optical Zone in Eyes With High Myopia With High Astigmatism After SMILE and FS-LASIK.

PURPOSE: To compare the functional optical zone (FOZ) in eyes with high myopia with high astigmatism after small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). METHODS: In total, 45 eyes of 45 patients with high myopia with astigmatism greater than 2.00 diopters (D) who underwent SMILE or FS-LASIK were enrolled. The FOZ, optical zone decentration, and corneal aberrations were analyzed using Scheimpflug imaging. These values were then compared between the two groups 6 months postoperatively. RESULTS: No postoperative complications were observed during follow-up. The mean FOZ diameter was 5.03 ± 0.31 mm for the FS-LASIK group and 5.24 ± 0.27 mm for the SMILE group (P = .007), corresponding to reductions of 1.18 ± 0.23 and 1.01 ± 0.21 mm, respectively, compared with the programmed optical zone (POZ) (P = .013). A significant difference was noted in the FOZ on the short axis between the two groups (P = .002), whereas no significant difference was observed on the long axis (P = .088). The FOZ area in the FS-LASIK and SMILE groups was 65.39 ± 6.14% and 70.09 ± 5.46% of the POZ area, respectively (P = .010). There was no significant difference in decentration between the two groups (0.29 ± 0.13 mm for the FS-LASIK group vs 0.30 ± 0.13 mm for the SMILE group, P = .798). A significant increase in spherical aberration was observed in the FS-LASIK group (P < .001). However, the induction of vertical coma was higher in the SMILE group than in the FS-LASIK group (P = .002). CONCLUSIONS: Eyes with high myopia with high astigmatism following SMILE achieved a larger FOZ and less spherical aberration but a larger vertical coma introduction than following FS-LASIK. [J Refract Surg. 2022;38(9):595-601.].