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Relevance. The study of the mechanisms of insufficiently rapid achievement of high visual acuity in the early postoperative period in the correction of myopia by the SMILE method is relevant. Purpose. To evaluate changes in corneal densitometry parameters after SMILE and FS-LASIK surgery in patients with moderate myopia. Material and methods. A study of 152 patients with moderate myopia was conducted, 68 were operated by SMILE and 84 – FS-LASIK. All procedures were performed using a VisuMax femtosecond laser and a MEL 80 excimer laser (Carl Zeiss Meditec, Germany). Assessment of visual acuity, corneal structure (OCT, Optovue, USA), corneal densitometry (Pentacam Scheimpflug, Germany) were performed before the operation, on the 1st, 5th day, 3, 6, 12 months after the operation. OCT scans were analyzed using the ImageJ program. Results. Оn the 1st day after SMILE, visual acuity (p=0.01) and transparency of the anterior and middle layers of the cornea were reduced than after FS-LASIK in the zone from 0 to 2 mm (p=0.045, p=0.001), from 2 to 6 mm (both p=0.001). These differences became statistically insignificant 5 days after surgery. By three and six months in the FS-ERASER group, the corneal transparency in the middle layers were reduced in the 0–2 mm and 2–6 mm zones (p=0.0001, p=0.001). In both groups, by 12 months, the corneal backscattering reached the values of the preoperative period (p>0,05). Conclusion. Refractive operations SMILE and FS-LASIK are accompanied by a decrease in corneal transparency, which is restored to preoperative values by 12 months. In the early postoperative period, an increase in densitometry indicators and a slower recovery of visual acuity after SMILE surgery may be due to active remodeling of the interface, which includes fragments of collagen fibrils and cellular components inside the intrastromal space. Key words: SMILE, FS-LASIK, densitometry, myopia

To compare long-term clinical outcomes following small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia and myopic astigmatism correction. In this retrospective study, we enrolled a total of 101 patients (101 eyes) who underwent SMILE or FS-LASIK 3 years prior. Measured parameters included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction and corneal wavefront aberrations. No significant differences in patient characteristics were found between the two groups. At the 3-year follow-up, UDVA was better than or equal to 20/20 in 90% and 85% (p=0.540) of the eyes; the efficacy indexes were 1.05±0.19 and 1.01±0.21 in the SMILE and FS-LASIK groups, respectively (p=0.352). Safety indexes were 1.19±0.17 and 1.15±0.20 in the SMILE and FS-LASIK groups, respectively (p=0.307). Eighty per cent and 65% of eyes were within ±0.50 D of the attempted spherical equivalent correction after SMILE and FS-LASIK, respectively (p=0.164). Vector analysis revealed no significant differences in astigmatic correction between the two groups (p>0.05). Surgically induced spherical aberration was higher in the FS-LASIK group than in the SMILE group (p<0.001). Long-term follow-up analysis suggested that both SMILE and FS-LASIK were safe and equally effective for myopic and astigmatic correction.

Ting Shao,1– 3 Hua Li,1– 3 Yusu Peng,1– 3 Jiafan Zhang,1– 3 Huifeng Wang,1– 3 Keli Long1– 3 1Eye Institute of Shandong First Medical University, Qingdao Eye Hospital of Shandong First Medical University, Qingdao, Shandong, People’s Republic of China; 2State Key Laboratory Cultivation Base, Shandong Key Laboratory of Eye Diseases, Qingdao, Shandong, People’s Republic of China; 3School of Ophthalmology, Shandong First Medical University, Qingdao, Shandong, People’s Republic of ChinaCorrespondence: Keli Long, Eye Institute of Shandong First Medical University, Qingdao Eye Hospital of Shandong First Medical University, No. 5. Yanerdao Road, Shi-Nan District, Qingdao, Shandong, 266000, People’s Republic of China, Email longkeli2002@aliyun.comPurpose: To compare the changes in corneal biomechanics and epithelial thickness after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in high myopia over − 8.00D patients with and without myopia regression.Methods: This retrospective case-control study included thirty-nine patients. Based on refractive status at one year after surgery, patients with a myopic shift ≥ 1.00 D were classified as the myopic regression group (R group, 33 eyes), while the remaining patients were classified as the normal group (N group, 42 eyes). Preoperative and postoperative visual outcomes, refraction, topography, corneal epithelial thickness, and corneal biomechanics were compared.Results: Ambrosio relational thickness to the horizontal profile (ARTh) at 3, 6, and 12 months postoperatively was significantly smaller in the R than in the N group, with mean differences of − 9.75 (95% confidence interval (CI): − 18.44 to − 1.04), p= 0.029; − 12.23 (95% CI: − 20.02 to − 4.42), p= 0.003; and − 9.47 (95% CI: − 16.86 to − 2.08), p= 0.013, respectively. Meanwhile, the stiffness parameter A1 (SP-A1) at 6 and 12 months after surgery was smaller in the R than in the N group, with mean differences of − 6.62 (95% CI: − 12.85 to − 0.37), p= 0.038 and − 7.26 (95% CI: − 13.79 to − 0.71), p= 0.030, respectively. The postoperative changes in SP-A1 at 6 and 12 months were significantly larger in the R group than in the N group (6.47, 95% CI: 1.04 to 11.91, p= 0.020; and 5.96, 95% CI: 0.37 to 11.52, p= 0.037, respectively). In addition, corneal epithelial thickness (CET) in different zones showed a significant negative correlation with refractive error at 12 months after surgery, with correlation coefficients ranging from − 0.55 to − 0.32 (all p< 0.05, with the central zone showing p< 0.001).Conclusion: Ultra-high myopic patients with post-FS-LASIK regression have poorer corneal biomechanics and greater central epithelial thickening, highlighting these factors as key susceptibility features for refractive instability. Early assessment of these parameters may help identify at-risk patients and guide personalized management to improve long-term outcomes.Keywords: myopic regression, FS-LASIK, biomechanics, epithelial thickness, ultra-high myopia

We aimed to evaluate the posterior corneal and anterior chamber changes following small incision lenticule extraction (SMILE) and femtosecond laser‐assisted laser in situ keratomileusis (FS‐LASIK). This retrospective study included 93 eyes for SMILE and 228 eyes for FS‐LASIK. Posterior corneal curvature, anterior chamber biometrics, and posterior corneal aberrations preoperatively and at 1 week and 3 months after surgery were evaluated. The correlation between surgical‐related factors and posterior corneal morphology changes, posterior corneal morphology changes, and posterior corneal aberration alterations were determined. There was an increase in mean posterior corneal radius (PCC R) and flat posterior corneal radius (PCC R1) and decrease in anterior chamber depth and anterior chamber volume in the SMILE and FS‐LASIK group (all p < 0.05). A significant difference was observed in posterior corneal higher‐order aberrations before and after the FS‐LASIK (p = 0.006). A negative correlation was found between alterations of PCC R and changes of posterior corneal spherical aberrations in the SMILE (r = −0.289) and FS‐LASIK group (r = −0.383). In conclusion, posterior corneal and anterior chamber biometrics are changed after SMILE and FS‐LASIK. Innovatively, we find that changes in posterior corneal morphology are correlated with posterior corneal aberration alterations. To evaluate the posterior corneal and anterior chamber changes following small incision lenticule extraction (SMILE) and femtosecond laser‐assisted laser in situ keratomileusis (FS‐LASIK). The correlations between surgical‐related factors and posterior corneal morphology changes, and between posterior corneal morphology changes and posterior corneal aberration alterations were also analyzed.

To compare the changes in corneal biomechanics and epithelial thickness after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in high myopia over -8.00D patients with and without myopia regression. This retrospective case-control study included thirty-nine patients. Based on refractive status at one year after surgery, patients with a myopic shift ≥1.00 D were classified as the myopic regression group (R group, 33 eyes), while the remaining patients were classified as the normal group (N group, 42 eyes). Preoperative and postoperative visual outcomes, refraction, topography, corneal epithelial thickness, and corneal biomechanics were compared. Ambrosio relational thickness to the horizontal profile (ARTh) at 3, 6, and 12 months postoperatively was significantly smaller in the R than in the N group, with mean differences of -9.75 (95% confidence interval (CI): -18.44 to -1.04), p= 0.029; -12.23 (95% CI: -20.02 to -4.42), p= 0.003; and -9.47 (95% CI: -16.86 to -2.08), p= 0.013, respectively. Meanwhile, the stiffness parameter A1 (SP-A1) at 6 and 12 months after surgery was smaller in the R than in the N group, with mean differences of -6.62 (95% CI: -12.85 to -0.37), p= 0.038 and -7.26 (95% CI: -13.79 to -0.71), p= 0.030, respectively. The postoperative changes in SP-A1 at 6 and 12 months were significantly larger in the R group than in the N group (6.47, 95% CI: 1.04 to 11.91, p= 0.020; and 5.96, 95% CI: 0.37 to 11.52, p= 0.037, respectively). In addition, corneal epithelial thickness (CET) in different zones showed a significant negative correlation with refractive error at 12 months after surgery, with correlation coefficients ranging from -0.55 to -0.32 (all p< 0.05, with the central zone showing p< 0.001). Ultra-high myopic patients with post-FS-LASIK regression have poorer corneal biomechanics and greater central epithelial thickening, highlighting these factors as key susceptibility features for refractive instability. Early assessment of these parameters may help identify at-risk patients and guide personalized management to improve long-term outcomes.

To assess the refractive outcomes, visual quality, and patient satisfaction after ray-tracing-guided femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for the correction of moderate-to-high myopia and myopic astigmatism. In this consecutive case series retrospective study, 51 patients (101 eyes) with moderate-to-high myopia and myopic astigmatism underwent ray-tracing-guided FS-LASIK. Visual acuity, manifest refraction, objective and subjective visual quality, patient satisfaction were assessed over 3 months. For objective visual quality, InnovEyes Sightmap was used to measure the higher-order aberrations (HOAs) over 5-mm optical zone, and Optical Quality Analysis System II was used to evaluate the modulation transfer function cut off (MTF ) frequency, Strehl ratio (SR), and ocular scattering index (OSI). Subjective visual quality was evaluated utilizing the National Eye Institute Refractive Error Quality of Life (NEI-RQL) questionnaire. Regarding visual and refractive outcomes, at 3 months, uncorrected distance visual acuity reached ≥ 20/20 in all eyes, ≥20/16 in 69% of eyes, and ≥20/12.5 in 18% of eyes. Best-corrected distance visual acuity was better in 61% of eyes. All eyes achieved manifest refractive spherical equivalent within ± 1.00 D and 86% of eyes achieved cylinder within ± 0.25 D. As for objective visual quality, total HOA increased significantly ( < 0.001), whereas spherical aberration showed no significant change ( = 0.225); no changes were found in MTF , SR, and OSI (all > 0.05). In terms of subjective visual quality, 100% of patients reported clear distance vision, and 96.10% had no near-reading difficulty. Investigation of patient satisfaction showed that 98.04% of patients were satisfied with the surgery, 98.04% would recommend it to others. Ray-tracing-guided FS-LASIK may be an effective, safe and predictable procedure for moderate-to-high myopia and myopic astigmatism. It yielded favorable refractive outcomes, maintained objective visual quality, and achieved high patient satisfaction.

Purpose: The objective of this study is to evaluate the in vivo corneal biomechanical response to three laser refractive surgeries. Methods: Two hundred and twenty-seven patients who submitted to transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted in-situ keratomileusis (FS-LASIK), or small-incision lenticule extraction (SMILE) were included in this study. All cases were examined with the Corvis ST preoperatively (up to 3 months) and postoperatively at 1, 3, and 6 months, and the differences in the main device parameters were assessed. The three groups were matched in age, gender ratio, corneal thickness, refractive error corrections, optical zone diameter, and intraocular pressure. They were also matched in the preoperative biomechanical metrics provided by the Corvis ST including stiffness parameter at first applanation (SP-A1), integrated inverse radius (IIR), deformation amplitude (DA), and deformation amplitude 2 mm away from apex and the apical deformation (DARatio2mm). Results: The results demonstrated a significant decrease post-operation in SP-A1 and significant increases in IIR, DA, and DARatio2mm ( p  < 0.05), all of which indicated reductions in overall corneal stiffness. Inter-procedure comparisons provided evidence that the smallest overall stiffness reduction was in the tPRK group, followed by the SMILE, and then the FS-LASIK group ( p  < 0.05). These results remained valid after correction for the change in CCT between pre and 6 months post-operation and for the percentage tissue altered. In all three surgery groups, higher degrees of refractive correction resulted in larger overall stiffness losses based on most of the biomechanical metrics. Conclusion: The corneal biomechanical response to the three surgery procedures varied significantly. With similar corneal thickness loss, the reductions in overall corneal stiffness were the highest in FS-LASIK and the lowest in tPRK.

To evaluate the impact of ocular residual astigmatism (ORA) on the astigmatic correction outcomes of wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG FS-LASIK) in myopic astigmatism patients. Retrospective cohort study. This study analyzed 90 patients (177 eyes) undergoing WFG FS-LASIK at Chongqing Medal Eye Institute between January 2015 and May 2021, all with complete follow-up data spanning 15 days–6 months postoperatively. Participants were categorized into three groups based on the ratio of ORA to refractive astigmatism (RA), and the axial difference between ORA and anterior corneal astigmatism (ACA): Group1 (42 eyes): |ORA|/|RA| < 1 and the axial difference between ORA and ACA was ≦ 45°. Group 2 (86 eyes): |ORA|/|RA| < 1 and the axial difference between ORA and ACA was > 45°. Group3 (49 eyes): |ORA|/|RA| > 1 and the axial difference between ORA and ACA was > 45°. Uncorrected distance visual acuity (UDVA) at 6 months postoperatively was compared among the three groups. Alpins vector analysis was performed to compare the accuracy of astigmatic correction, quantified by: Angle of error (AE): axial deviation between the surgically induced astigmatism (SIA) and target induced astigmatism (TIA); Correction index (CI): ratio of SIA to TIA (ideal value = 1.0). The mean |AE| values significantly differed among groups ( P  < 0.05), being lowest in Group 1 (9.29°) and highest in Group 3 (26.64°). Correction index (CI) defined as the ratio of SIA to TIA. The mean CI values were1.00 (Group 1), 1.19 (Group 2) and 3.26 (Group 3).No statistically significant differences were observed in postoperative UDVA among the three groups ( P  > 0.05). In WGF FS-LASIK, the consistency between the axis of ORA and ACA affects the degree of deviation in astigmatic axis correction, but had no significant impact on UDVA.

To compare the long-term outcomes of monovision surgery using implantable collamer lens (ICL) V4c and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in myopic patients with early presbyopia. This case series study included 48 eyes of 24 patients (male/female: 10/14, mean age 45.50 ± 3.82 years) and followed-up for 4.5 years (54.00 ± 9.77 months). Patients were examined for spherical equivalent, uncorrected distance visual acuity, corrected distance visual acuity, intraocular pressure, presbyopic add power, visual acuity (VA) (logMAR) of dominant eyes (D-eye), non-dominant eyes (nD-eye), and both eyes (Bi) at 0.4 m, 0.8 m, and 5 m, corneal wavefront aberration, and contrast sensitivity (CS). All surgeries were uneventful. The safety indices of ICL V4c group and FS-LASIK group were 1.17 ± 0.30 and 0.98 ± 0.20 ( p  < 0.05), and the efficacy indices were 0.79 ± 0.07 and 0.52 ± 0.07 ( p  < 0.05) respectively. The binocular VA (logMAR) of ICL V4c group and FS-LASIK group at 5.0 m were: 0.02 ± 0.11, 0.18 ± 0.30; 0.8 m: 0.09 ± 0.12, − 0.01 ± 0.11; 0.4 m: − 0.02 ± 0.06, − 0.03 ± 0.08, ( p  > 0.05 at three distances). Compared with ICL V4c group, lower CS was observed at 1.0 cpd in the FS-LASIK group (1.07 ± 0.31 vs. 0.80 ± 0.51, p  = 0.043). Monovision surgery using ICL V4c and FS-LASIK provides good binocular visual acuity at near-to-far distances in myopia patients in the presbyopia age group.

To compare the predictability of central corneal thickness (CCT) reduction in myopic patients undergoing femtosecond laser-assisted in situ keratomileusis (FS-LASIK) using the aberration-optimized (Triple-A) and topography-guided (TG) profiles on the MEL 90 platform. This study involved 82 patients, treating one eye with the Triple-A profile and the other with the TG profile on the MEL 90, with an average spherical equivalent of − 5.76 ± 2.02 D (Triple-A) and − 5.79 ± 1.90 D (TG). Refractive assessments were done preoperatively and at 1 day, 1 week, 1 month, and 3 months postoperatively. Achieved CCT reduction (via Pentacam) = CCT pre-op -CCT post-op . The MEL 90 platform provided the predicted CCT reduction, and comparative statistical methods and linear regression analyses were conducted. The 3-month CCT reduction was underestimated by 5.18 ± 7.41 μm in the Triple-A group ( P  < 0.0001) and by 14.44 ± 10.10 μm in the TG group ( P  < 0.0001). The planned CCT reduction in the TG group was much smaller than that in the Triple-A group ( P  < 0.0001), yet the achieved reduction was greater ( P  = 0.034), mainly in moderate myopia ( P  = 0.012). Moreover, subgroup analyses indicated that these differences were present exclusively in moderate to high myopia. As the corrected refraction increased, the planned-achieved difference (PAD) also increased. For patients with moderate and high myopia, both Triple-A and TG profiles of FS-LASIK on the MEL 90 laser platform may underestimate the CCT reduction. TG LASIK does not save corneal tissue but even consumes more of it in moderate myopia.