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AIM: To explore the clinical effect of small incision lenticule extraction(SMILE)on the treatment of myopic anisometropia.METHODS: Clinical data of 76 patients(146 eyes)with myopic anisometropia who received SMILE or femtosecond assisted laser in situ keratomileusis(FS-LASIK)in our hospital from January 2021 to December 2022 were retrospectively analyzed. The patients were divided into SMILE group(39 cases, 77 eyes)and FS-LASIK group(37 cases, 69 eyes)according to surgical methods. Uncorrected visual acuity(UCVA), diopter, anisometropia, corneal aberration and occurrence of postoperative complications were compared between the two groups at 1 wk, 1 and 3 mo after surgery.RESULTS: The UCVA of the two groups was improved after surgery compared with that before surgery, and the coma, trefoil, spherical aberration and total higher-order aberration were significantly increased compared to those before surgery(P<0.05), and the coma, trefoil, spherical aberration and total higher-order aberration in the FS-LASIK group were significantly higher than those in the SMILE group(P<0.05). After follow-up to 3 mo after surgery, the incidence of postoperative complications was significantly lower in the SMILE group than that in the FS-LASIK group(5.2% vs 15.9%, P<0.05).CONCLUSION: Both SMILE and FS-LASIK can effectively enhance the UCVA and improve the visual quality in patients with myopic anisometropia, but SMILE has lower corneal higher order aberrations, lower incidence of postoperative complications and better overall effect.
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AIM: To evaluate the clinical efficacy of corneal stromal lenticule-combined accelerated transepithelial corneal collagen cross-linking(SC-A-TE-CXL)in the treatment of severe keratoconus.METHODS: Prospective before-after self-control study. A total of 10 cases(14 eyes)of severe keratoconus with the thinnest corneal thickness(including epithelium)less than 400 μm were collected from March 2019 to July 2022 at the ophthalmology department of Affiliated Eye Hospital of Nanjing Medical University. Among them, 8 males(12 eyes)and 2 females(2 eyes)were treated with SC-A-TE-CXL. Corneal curvature, uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), the thinnest corneal thickness(TCT), central corneal thickness(CCT), non-contact intraocular pressure, endothelial cell density(ECD)and anterior or posterior elevations at the thinnest point before surgery and at 1, 3, 6 and 12 mo postoperatively were observed and recorded, as well as corneal cross-linking depth at 1 mo postoperatively.RESULTS: UCVA and BCVA at 1, 3, 6, and 12 mo after SC-A-TE-CXL were higher than those preoperatively, but there were no differences(F=0.793, P=0.535; F=0.783, P=0.542). K1, K2, Km and Kmax decreased at each time point postoperatively compared with those preoperatively, but there were no differences(F=0.627, P=0.574; F=1.264, P=0.296; F=0.727, P=0.520; F=1.115, P=0.359). Anterior and posterior elevations at the thinnest point both decreased compared with those preoperatively, but the differences were not statistically significant(F=1.046, P=0.359; F=1.164, P=0.337). The non-contact intraocular pressure at each time point postoperatively was higher than that preoperatively, but the differences were not statistically significant(F=0.814, P=0.522). There were no differences in CCT and TCT at any time points of the follow-ups compared with those preoperatively(F=0.931, P=0.453; F=0.782, P=0.542). There was no difference in ECD at 12 mo postoperatively versus preoperative value(t=1.266, P=0.228). At 1 mo postoperatively, anterior segment optical coherence tomography(AS-OCT)exhibited an increase of density in the anterior stroma, and there was a demarcation line with an average depth of 124.07±25.13 μm.CONCLUSION: SC-A-TE-CXL can be considered as a surgical treatment for severe keratoconus, which can delay the progression of severe keratoconus with high safety. However, the long-term efficacy of this treatment requires further observation.
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AIM:To investigate the effect of small incision lenticule extraction(SMILE)on the treatment of myopia patients, and the impact on corneal biomechanics.METHODS:Retrospective study. A total of 120 myopic patients(240 eyes)who were scheduled to undergo corneal refractive surgery in Anyang Eye Hospital from January 2020 to December 2021 were selected. The patients were divided into SMILE group(64 patients, 128 eyes)and transepithelial photorefractive keratectomy(TransPRK)group(56 patients, 112 eyes)according to the surgical treatment method. The two groups were compared in terms of uncorrected visual acuity, corneal biomechanics, corneal endothelial cell count, posterior corneal surface height and corneal surface regularity index at 1, 7 d, 1, 3, 6 mo and 1 a after surgery, and surgical complications.RESULTS:The uncorrected visual acuity of the SMILE group at 1, 7 d and 1 mo after surgery was better than that of the TransPRK group(all P<0.001), but there was no statistically significant difference between the groups at 3, 6 mo and 1 a after surgery(all P>0.05). Compared with preoperative values, corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, corneal resistance factor, and corneal hysteresis in both groups showed a first decreasing and then increasing trend after surgery. The corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, corneal resistance factor, and corneal hysteresis in the SMILE group at 1, 7 d and 1 mo after surgery were higher than those in the TransPRK group(all P<0.05), but there was no statistically significant difference between the groups at 3, 6 mo and 1 a after surgery(all P>0.05). There were no significant changes of corneal endothelial cell count and corneal posterior surface height in the two groups after surgery(all P>0.05). Furthermore, corneal surface regularity index of the two groups showed a first increasing and then decreasing trend after surgery, with no statistically significant difference between the groups(P>0.05), and there was no statistically significant difference in the incidence of postoperative complications between the groups(P>0.05).CONCLUSION:Compared with TransPRK, SMILE has less influence on corneal biomechanics, and better visual recovery in the early stage. There is no difference in long-term visual acuity between the two surgeries, and both have good safety and effectiveness.
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AIM: To evaluate the clinical outcomes of using the cross-positioning method for correcting low and moderate astigmatism during small incision lenticule extraction(SMILE)surgery with Alpins vector analysis.METHODS: A total of 50 patients(81 eyes)with low and moderate astigmatism with the rule ≤1.50 D who underwent SMILE surgery at the laser myopia treatment center of Xi'an No.1 Hospital from May 2022 to November 2022 were included in the prospective randomized controlled study, and they were divided into two groups according to the random table, with 25 case(41 eyes)in cross-positioning group and 25 cases(40 eyes)in control group. In the cross-positioning group, the patients' head position was adjusted based on the cross intersection lines before the standard SMILE procedure, aligning the lateral canthi with the horizontal line and the midpoint of the eyebrows and the nose bridge with the vertical line. Postoperative visual acuity and refractive results at 3 mo were observed in both groups, and astigmatic changes were analyzed and evaluated using the Alpins vector analysis method.RESULTS: During the follow-up period, 6 cases(11 eyes)in the cross-positioning group were lost to follow-up, while in the control group, 8 cases(14 eyes)were lost to follow-up, with 19 cases(30 eyes)and 17 cases(26 eyes)finally included in the cross-positioning group and the control group, respectively. At 3 mo postoperatively, the uncorrected visual acuity(UCVA)of both groups' operated eyes was ≥1.0, and no serious complications occurred, with no significant differences in UCVA, best corrected visual acuity(BCVA), spherical power, and spherical equivalent between the cross-positioning group and the control group(all P&#x003E;0.05). The cylindrical power in the cross-positioning group was 0.00(0.00, 0.00)D, which was lower than -0.13(-0.50, 0.00)D in the control group(P=0.01). The vector analysis results showed that the difference vector(DV)in the cross-positioning group was lower than that in the control group [0.00(0.00, 0.00)vs 0.13(0.00, 0.50), P=0.01], and the index of success(IOS)was better than that of the control group [0.00(0.00, 0.00)vs 0.18(0.00, 0.77), P&#x003C;0.01]. At 3 mo postoperatively, 26(87%)and 15(58%)eyes in the cross-positioning group and control groups achieved an angle of error(AE)within ±5°, respectively.CONCLUSION: The cross positioning method was used to calibrate the patients' head position during SMILE surgery, which reduced the axial position error and improved the accuracy of SMILE in correcting low and moderate astigmatism.
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AIM:To explore the effect of high aspherical lenticule on controlling low myopia.METHODS: Prospective study. A total of 100 patients aged 7 to 12 years old with low myopia who visited our hospital from May 1 to 31, 2022 were collected. They were divided into two groups with 50 cases in each group according to the wishes of patients. The control group was given single vision glasses after optometry, while the study group was given high aspherical lenticule. The myopia progression(absolute value), axial length(AL)growth, transition rate to moderate myopia, and AL negative growth rate over 6 mo and 1 a were compared between the two groups.RESULTS: The myopia progression and the AL growth of study group was lower than that of the control group after 6 mo and 1 a(all P&#x003C;0.001).The negative growth rate of AL after 6 mo of treatment was significantly higher than that of the control group(P&#x003C;0.001). The transition rate to moderate myopia between the two groups was not statistically significant(P=0.62); while the transition rate to moderate myopia in the study group was significantly lower than that in the control group after wearing lens for 1 a(P&#x003C;0.001), and there was no statistically significant difference in AL negative growth rate between the two groups(P=0.12). Compare with single vision glasses, high aspherical lenticule achieved an 88.2% control rate for low myopia progression over 6mo and a 90.0% control rate of AL growth. The control rate for low myopia to moderate myopia was 66.7%; while the control rate of myopia progression growth was 75.6% after wearing lens for 1a, the control rate of AL growth was 69.2%, and the control rate of the transition rate to moderate myopia was 88.9%.CONCLUSION: For children and adolescents aged 7 to 12 with low myopia, high aspherical lenticule was more effective than single vision glasses in controlling myopia, making it one of the optimal choices for myopia control.
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Purpose: To compare the visual outcomes in patients undergoing small?incision lenticule extraction (SMILE) for correction of myopic astigmatism (??1.50 D) with or without manual cyclotorsion compensation. Methods: A prospective, double?blinded, randomized, contralateral study was conducted in the refractive services of a tertiary eye care center. Eligible patients with bilateral high myopic astigmatism (?1.5 D) and intraoperative cyclotorsion (?5°) undergoing SMILE between June 2018 and May 2019 were included. Cyclotorsion compensation was performed using triple centration method before femtosecond laser delivery. Uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) measurement, manifest refraction, slit?lamp biomicroscopy, and corneal tomography were performed preoperatively and at 1 and 3 months’ postoperative visit. Astigmatic outcomes were analyzed using Alpins criteria. Results: A total of 30 patients (60 eyes) were included in this study. The patients underwent bilateral SMILE surgery, with manual cyclotorsion compensation in one eye (CC group, n = 30 eyes) and no cyclotorsion compensation in the other eye (NCC group, n = 30 eyes). Preoperative astigmatism and intraoperative cyclotorsion were ?2.0 D and 7.03° ± 1.06° (CC) and ?1.75 D and 7.24° ± 0.98° (NCC) (P = 0.472 and 0.240, respectively). No significant differences were noted in mean refractive spherical equivalent (MRSE), UDVA, CDVA, and refractive error between the two groups at 3 months’ postoperative visit. Astigmatic outcomes measured using Alpins criteria demonstrated no significant difference between the two cohorts. Conclusion: The cyclotorsion compensation technique provided no additional advantage in terms of astigmatic outcomes or postoperative visual quality, in eyes with high preoperative astigmatism and intraoperative cyclotorsion.
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Purpose: To evaluate the postoperative visual outcomes, that is, corneal higher?order aberrations (HOAs) and visual quality, of patients with an angle kappa greater than 0.30 mm who underwent angle kappa adjustment during small?incision lenticule extraction (SMILE) 2 years after surgery compared to eyes with an angle kappa less than 0.30 mm. Methods: This was a retrospective study and included 12 patients from October 2019 to December 2019 who underwent the SMILE procedure for correction of myopia and myopic astigmatism and had one eye with a large kappa angle and another eye with a small kappa angle. Twenty?four months after surgery, an optical quality analysis system (OQAS II; Visiometrics, Terrassa, Spain) was used to measure the modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI). HOAs were measured with a Tracey iTrace Visual Function Analyzer (Tracey version 6.1.0; Tracey Technologies, Houston, TX, USA). Assessment of subjective visual quality was achieved using the quality of vision (QOV) questionnaire. Results: At 24 months postoperatively, the mean spherical equivalent (SE) refraction was ? 0.32 ± 0.40 and ? 0.31 ± 0.35 in the S?kappa group (kappa <0.3 mm) and the L?kappa group (kappa ?0.3 mm), respectively (P > 0.05). The mean OSI was 0.73 ± 0.32 and 0.81 ± 0.47, respectively (P > 0.05). There was no significant difference in MTFcutoff and Strehl2D ratio between the two groups (P > 0.05). Total HOA, coma, spherical, trefoil, and secondary astigmatism were not significantly different (P > 0.05) between the two groups. Conclusion: Adjustment of angle kappa during SMILE helps reduce the decentration, results in less HOAs, and promotes visual quality. It provides a reliable method to optimize the treatment concentration in SMILE.
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Purpose: To compare visual outcomes of early enhancement following small incision lenticule extraction (SMILE) versus laser in situ keratomileusis (LASIK). Methods: Retrospective analysis of eyes (patients operated in the setting of a tertiary eye care hospital between 2014 and 2020) requiring early enhancement (within one year of primary surgery) was conducted. Stability of refractive error, corneal tomography, and anterior segment Optical Coherence Tomography (AS-OCT) for epithelial thickness was performed. The correction post regression was done using photorefractive keratectomy and flap lift in eyes, wherein the primary procedure was SMILE and LASIK, respectively. Pre- and post enhancement corrected and uncorrected distance visual acuity (CDVA and UDVA), mean refractive spherical equivalent (MRSE), and cylinder were analyzed. IBM SPSS statistical software. Results: In total, 6350 and 8176 eyes post SMILE and LASIK, respectively, were analyzed. Of these, 32 eyes of 26 patients (0.5%) post SMILE and 36 eyes of 32 patients (0.44%) post-LASIK required enhancement. Post enhancement (flap lift in LASIK, and PRK in SMILE group) UDVA was logMAR 0.02 ± 0.05 and 0.09 ± 0.16 (P = 0.009), respectively. There was no significant difference between the refractive sphere (P = 0.33) and MRSE (P = 0.09). In total, 62.5% of the eyes in the SMILE group and 80.5% in the LASIK group had a UDVA of 20/20 or better (P = 0.04). Conclusion: PRK post SMILE demonstrated comparable results to flap lift post LASIK and is a safe and effective approach for early enhancement post SMILE.
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AIM: To analyze the effect of full-femtosecond small incision lenticule extraction(SMILE)on the treatment of high myopia based on propensity score matching.METHODS: A total of 48 cases(48 eyes)of high myopia patients who underwent SMILE surgery in our hospital from May 2019 to May 2021 were selected as the observation group, and 48 cases(48 eyes)of high myopia patients who underwent FS-LASIK surgery were matched using propensity score matching as the control group. Follow up for 6mo after surgery, the changes in cylindrical, central corneal thickness, uncorrected visual acuity(UCVA), corneal endothelial cell related indicators [percentage of hexagonal endothelial cells(6A), coefficient of variation(CV)of endothelial cell area, central corneal endothelial cell density(ECD)] and corneal biomechanical indicators [simulated Goldman intraocular pressure(IOPg), corneal hysteresis(CH), corneal resistance factor(CRF), corneal compensated intraocular pressure(IOPcc)] between the two groups were compared, and the incidence of complications in both groups of patients was recorded.RESULTS: Both groups of patients showed significant improvements in cylindrical and UCVA at 3 and 6mo after surgery, as well as decreased central corneal thickness, corneal endothelial cells, and corneal biomechanics related indicators. The changes in the observation group were more significant(all P<0.05). During the follow-up period, there was no significant difference in the incidence of complications between the observation group and the control group(8% vs. 17%, P>0.05).CONCLUSION: SMILE has a definite effect on patients with high myopia and is helpful to improve visual acuity.
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AIM: To investigate the effect of different preoperative corneal curvature on the size of optical deformation area after femtosecond laser small incision lens extraction(SMILE).METHODS:A prospective study was conducted on 108 consecutive patients who underwent SMILE surgery in our hospital from February 2021 to January 2022. Considering the association between both eyes, only the left eye of each patient was studied. According to the average anterior corneal surface curvature in preoperative, the patients were divided into three groups: Km<42.0D group(n=30), Km>47.0D group(n=26)and conventional corneal curvature group(n=52)with 42.0D≤Km≤47.0D. All patients underwent standardized SMILE surgery, and the laser ablation diameter was 6.5mm. The diameters of optical deformation areas in the three groups were compared at 6mo after operation.RESULTS:There was no significant difference in preoperative data among the three groups except for the mean curvature of the anterior corneal surface(all P>0.05), and there was no significant difference in uncorrected distance visual acuity(UDVA)and subjective refraction at 6mo after operation(all P>0.05). The diameters of the optical deformation zone in the Km<42.0D group, Km>47.0D group and the conventional corneal curvature group were 6.54±0.14, 6.32±0.13, 6.45±0.15mm respectively(F=19.238, P<0.05). The optical area diameter of the group with flat corneal curvature was larger than that of the group with conventional corneal curvature and the group with steeper corneal curvature(P<0.05). The diameter of optical zone in the conventional curvature group was larger than that in the Km>47.0D group(P<0.05).CONCLUSION: When the preset laser cutting diameter is the same, the steeper the corneal curvature before operation, the smaller the diameter of the optical deformation area after operation.
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AIM: To compare the changes in corneal densitometry after small incision lenticule extraction(SMILE)and femtosecond laser in situ keratomileusis(FS-LASIK)and investigate the effect of corneal interface haze on vision after SMILE.METHODS: Prospective cohort study. A total of 93 patients(186 eyes)who were scheduled to undergo refractive surgery at the Ophthalmic Refractive Surgery Center of the Affiliated Hospital of Nantong University from May 2020 to October 2021 were included in the study, and there were 48 patients(96 eyes)in the SMILE group and 45 patients(90 eyes)in the FS-LASIK group. The changes in corneal densitometry, spherical equivalent(SE), and uncorrected visual acuity(UCVA)were observed and compared between the two groups before and at 1d, 1wk, 1, 3 and 6mo after surgery.RESULTS: The 93 patients all successfully completed the surgery, and there were no related complications during and after the surgery, and there were no lost cases. The UCVA of FS-LASIK group was 0.044±0.064 and -0.001±0.065 respectively at 1d and 1wk after surgery, which was better than that of SMILE group(0.102±0.077 and 0.023±0.064; all P<0.05). There was no statistical difference in the SE between the two groups at the postoperative follow-ups(P>0.05). The corneal densitometry values at 0-2 and 2-6 mm from corneal vertex and total corneal densitometry at 1d postoperatively in the FS-LASIK group were 18.0(17.5, 18.6), 16.2(15.6, 16.7)and 16.7(16.1, 17.3), which were lower than those of SMILE group [18.6(18.1, 19.3), 16.8(16.4, 17.4), 17.2(16.6, 17.8)](all P<0.05); The corneal densitometry values at 0-2 and 2-6 mm from corneal vertex and total corneal densitometry at 1wk postoperatively in the FS-LASIK group were 17.2(16.7, 17.6), 15.5(15.0, 15.9)and 15.9(15.3, 16.7), which were lower than those of SMILE group [17.6(17.1, 18.3), 16.0(15.6, 16.5), 16.6(15.9, 17.1)](all P<0.05).CONCLUSIONS: The transient interface haze after SMILE is responsible for the early higher corneal densitometry than FS-LASIK. The presence of interface haze is probably a factor for the quality of vision.
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AIM: To compare the efficacy of and without small incision lenticule extraction(SMILE)with cyclotorsion compensation for astigmatism correction.METHODS: PubMed, Web of Science, EMBASE, Cochrane and CNKI, VIP, CBM, and Wan Fang Data were searched for clinically controlled studies from January 2010 to August 2022, including an experimental group with cyclotorsion compensation during SMILE and a control group without cyclotorsion compensation during SMILE. After literature screening, quality evaluation, and data extraction by two researchers independently, the Meta-analysis of uncorrected distance visual acuity(UDVA), residual astigmatism, vector analysis indicators for measuring the astigmatism correction including absolute value of angle of error(|AE|)and magnitude error(ME), and post-operative total higher order aberrations, spherical aberration and coma was carried out with Stata 16.0 software.RESULTS: Seven studies with a total of 846 eyes(442 in the experimental group, 404 in the control group)were finally included. The Meta-analysis showed that there were significant differences in the percentage of eyes with residual astigmatism ≥1.00D(OR=0.17, 95%CI: 0.06～0.49, P<0.01), |AE|(WMD=-1.56, 95%CI: -2.68～-0.45, P<0.01), the coma(WMD=0.06, 95%CI: -0.08～-0.04, P<0.01), and the total higher order aberrations(WMD=-0.04, 95%CI: -0.06～-0.02, P<0.01). However, there were no differences in the postoperative UDVA(WMD=0.00, 95%CI: -0.02～0.01, P=0.54), residual astigmatism(WMD=0.08, 95%CI: -0.02～0.18, P=0.10), ME(WMD=-0.01, 95%CI: -0.14～0.12, P=0.85), and the spherical aberration(WMD=0.03, 95%CI: -0.07～0.13, P=0.52).CONCLUSION: Cyclotorsion compensation in SMILE can reduce the angular error caused by eye rotation during astigmatism correction. It also decreases postoperative residual astigmatism. Overall, the SMILE with cyclotorsion compensation is superior in clinical efficacy of the precise correction of astigmatism.
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AIM: To observe the epithelial remodeling of femtosecond laser-assisted stromal lenticule addition keratoplasty combined with corneal collagen cross-linking(SLAK-CXL)in patients with progressive keratoconus, investigate the remodeling rules of corneal epithelial and influencing factors, and provide clinical data for further refractive correction.METHODS: Retrospective and observational study. A total of 28 keratoconus patients(29 eyes)who received SLAK-CXL from September 2020 to October 2021 were included. Preoperative and postoperative visual acuity, intraocular pressure(IOP), diopter, keratometry and corneal epithelial thickness(CET)were recorded. The trend of CET change was observed. The factors affecting CET were analyzed according to the thickness and depth of the lenticule.RESULTS: Flattest meridian keratometry(Kf)and steepest meridian keratometry(Ks)at 1mo postoperatively were significantly larger than those preoperatively(P<0.05). The thinnest corneal thickness(TCT)at 1, 2, 6mo and 1a postoperatively were significantly larger than preoperative(P<0.05). The CET changed with time, with the central CET showing a larger variation tendency. The CET of superior, superior nasal, nasal, superior temporal in paracentral area were thinned, the CET of superior, temporal, superior temporal in midperipheral area were thinned, while the CET of superior nasal was thickened in peripheral area at 1, 2, 6mo and 1a postoperatively. The variation of CET was not correlated with the thickness or depth of lenticule at 1a postoperatively(P>0.05).CONCLUSIONS: It is firstly found that the corneal morphology has changed after SLAK-CXL. CET decreases and then increases and then decreases again. At 1a postoperatively, the CET of the central and paracentral areas is thinner, while the CET of the midperipheral and peripheral areas is thicker. The degree of epithelial remodeling is not correlated with lenticule thickness or depth.
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AIM: To observe and compare the changes in retinal peripheral refraction and aberrations after femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)versus small incision lenticule extraction(SMILE)for myopia correction.METHODS: A total of 71 patients(71 eyes)with myopia who underwent FS-LASIK from October 2022 to April 2023 in our hospital were selected as the FS-LASIK group, and 80 patients(80 eyes)with myopia who underwent SMILE were selected as the SMILE group. All patients underwent corneal wavefront aberration measurement and multispectral refractive topography preoperatively and 3mo postoperatively, as well as refraction difference value(RDV)in the range of 0°～10°, 10°～20°, 20°～30°, 30°～40°, and 40°～53° in the annulus of the retina, which were recorded as RDV-(0°～10°), RDV-(10°～20°), RDV-(20°～30°), RDV-(30°～40°), and RDV-(40°～53°). The results of two groups of patients were compared.RESULTS: No significant differences were observed in RDV-(0°～10°), RDV-(10°～20°), RDV-(20°～30°), RDV-(30°～40°), RDV-(40°～53°)between the two groups at 3mo post-operation(all P>0.05). Furthermore, the RDV-(20°～30°), RDV-(30°～40°)and RDV-(40°～53°)of the two groups at 3mo postoperatively were all significantly lower than those preoperatively(all P<0.05). The changes in coma(horizontal)and spherical aberration(SA)at 3mo postoperatively were smaller in the SMILE group [0.106(0.056, 0.171)and 0.115(0.081, 0.182)μm] than in the FS-LASIK group [0.206(0.104, 0.355)and 0.197(0.128, 0.254)μm](Z=-4.170, -5.016, all P<0.05). A negative correlation was found between postoperative SA and postoperative RDV-(10°～53°)(rs=-0.205, -0.181, -0.226, -0.244, all P<0.05).CONCLUSION: Both FS-LASIK and SMILE reduced retinal hyperopic defocus in the peripapillary macular range of 20°～53° eccentricity, and the postoperative changes in coma(horizontal)and SA were smaller with SMILE than with FS-LASIK. There was a certain correlation between postoperative SA and postoperative retinal peripheral defocus.
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Femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)and small incision lenticule extraction(SMILE)are the mainstream corneal refractive surgeries at present. Despite efficacy, safety and predictability they have showed in refractive error correction, there are still complications relating to femtosecond laser, such as suction loss and opaque bubble layer(OBL), due to that the production of corneal flap or lenticule is dependent on the femtosecond laser. OBL is a complication that is unique to femtosecond laser surgery and the bubbles are generated from photo-disruptive effect towards corneal tissues which consisted of water vapor and carbon dioxide, and OBL gradually formed when the bubbles are trapped in the stroma. The bubbles can influence the intraoperative manipulation and postoperative visual quality. This review discusses the mechanism, grading, classification, and influencing factors of OBL and its effects on intraoperative manipulations and postoperative recovery, in the hope of providing reference and basis for further clinical studies.
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AIM:To evaluate the changes in corneal biomechanics of patients with moderate refractive error after receiving small-incision lenticule extraction(SMILE)and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)using the corneal visualization Scheimpflug technology(Corvis ST).METHODS:Prospective cohort study. A total of 65 moderate myopia patients(65 eyes)who were scheduled to undergo refractive surgery at the Ophthalmic Refractive Surgery Center of the Ningxia Eye Hospital from November 2020 to November 2021 were included in the study, and there were 30 eyes in the SMILE group and 35 eyes in the FS-LASIK group. The changes in corneal biomechanical parameters, including integrated radius(IR), inverse concave radius(ICR), deformation amplitude ratio 2mm(DAR2), stiffness parameter at first applanation(SP-A1), ambrosio relational thickness(ARTh)and the central curvature radius at highest concavity(HC-Radius)were observed by Corvis ST between both groups preoperatively and 1 and 3mo postoperatively.RESULTS: There were no statistical significance in biomechanical parameters between two groups of patients 1 and 3mo postoperatively(P&#x003E;0.05). IR, ICR and DAR2 of each groups of patients 1 and 3mo postoperatively were significantly increased than those preoperatively, and SP-A1, ARTh and HC-Radius were significantly decreased than those preoperatively(all P&#x003C;0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P&#x003E;0.05). In addition, a positive correlation was found between central corneal thickness(CCT)and ARTh and SP-A1 of the two groups of patients at 3mo postoperatively(FS-LASIK group: r=0.727, 0.819, SMLIE group: r=0.683, 0.434, all P&#x003C;0.05), while a negative correlation was found between CCT and IR and ICR at 3mo postoperatively.(FS-LASIK group: r=-0.697, -0.622, SMLIE group: r=-0.447, -0.491, all P&#x003C;0.05).CONCLUSION:For patients with moderate myopia, both SMILE and FS-LASIK can reduce corneal biomechanical stability. Both surgeries showed no significant differences in the effect on biomechanical, and the biomechanical has been stabilized at 1mo postoperatively. A correlation was found between postoperative CCT and ARTh, SP-A1, IR and ICR.
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Objective:To compare the changes in functional optical zone (FOZ) and corneal morphology in myopes between femtosecond small incision laser lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK).Methods:A cohort study was performed.A total of 94 patients (94 eyes) who underwent FS-LASIK or SMILE at Eye Hospital, Wenzhou Medical University from March to December 2021 were enrolled.The selected patients were divided into a SMILE group (46 cases, 46 eyes) and an FS-LASIK group (48 cases, 48 eyes) according to the surgical procedure, and the follow-up period was 6 months.The primary outcome measures were postoperative changes in corneal FOZ and Q-value, and the secondary outcome measures were changes in central corneal thickness (CCT) and mean corneal curvature (Km). Corneal Q-value, horizontal and vertical FOZ diameters, CCT, and Km were recorded before surgery and at 1 day, 1 week, 1 month, and 6 months after surgery using the Pentacam anterior segment analysis system, and the differences in each parameter and the trends of changes between the two groups were compared.This study adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Eye Hospital, Wenzhou Medical University (No.2021-034-k-27). Written informed consent was obtained from each subject.Results:There were statistically significant overall differences in the postoperative horizontal and vertical FOZ diameters between the two groups (horizontal diameter: Fgroup=7.06, P<0.001; Ftime=64.18, P=0.001; vertical diameter: Fgroup=11.08, P<0.001; Ftime=77.14, P<0.001). The horizontal and vertical FOZ diameters were significantly larger in SMILE group than in FS-LASIK group at various postoperative time points, and the differences were statistically significant (all at P<0.001). In the two groups, the postoperative 1-week, 1-month and 6-month horizontal FOZ diameters and the postoperative 1-week and 1-month vertical FOZ diameters were smaller than the postoperative 1-day ones, and the differences were statistically significant (all at P<0.05). There were significant overall differences in Q-values at different postoperative time points between the two groups ( Fgrouup=53.11, P=0.019; Ftime=29.18, P<0.001). The postoperative 1-day, 1-week, and 1-month Q-values of FS-LASIK group were significantly higher than those of SMILE group (all at P<0.05). The postoperative 1-week Q-value was significantly larger than the postoperative 1-day value in SMILE group ( P<0.001). The postoperative Q-values gradually decreased with time in FS-LASIK group, with significant pairwise differences at all adjacent time points (all at P<0.001). There were significant differences in CCT at various postoperative time points between the two groups ( Ftime=21.43, P<0.01). In FS-LASIK group, the CCT was decreased at 1 week than 1 day after surgery and was increased at 6 months than 1 week after surgery, and the differences were statistically significant (all at P<0.05). In SMILE group, the postoperative 1-week, 1-month and 6-month CCT was increased in comparison with the postoperative 1-day value, and the differences were statistically significant (all at P<0.05). There was no significant overall difference in the Km between the two groups ( Fgroup=27.29, P=0.41). There were significant pairwise differences in the Km at different postoperative time points between the two groups (all at P<0.001). The postoperative 6-month Km was smaller than the postoperative 1-day value in SMILE group, and the postoperative 6-month Km was greater than the postoperative 1-day value in FS-LASIK group (both at P<0.05). Conclusions:The FOZ shows a trend of gradual reduction within a month after SMILE and FS-LASIK.The FOZ is larger after SMILE than after FS-LASIK.The morphologic stability of corneal FOZ is better after SMILE than after FS-LASIK.
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Objective:To investigate the differences and changes in early postoperative visual quality after small incision lenticule extraction (SMILE) and smart pulse technology-assisted transepithelial photorefractive keratectomy (SPT-TransPRK).Methods:A cohort study was performed.A total of 92 patients (92 eyes) who underwent corneal laser refractive surgery were enrolled in Dalian Third People's Hospital Affiliated to Dalian Medical University from February 2021 to May 2021.The data from the right eye were collected for analysis.The patients were divided into SMILE group (40 patients, 40 eyes) and SPT-TransPRK group (52 patients, 52 eyes). Preoperative, 1- and 3-month postoperative visual acuity were measured to calculate the effectiveness, which was defined as the ratio of postoperative uncorrected visual acuity (UCVA) to preoperative best corrected visual acuity.Refraction was measured by an AR-1 autorefractor.Corneal higher-order aberration (HOA) including total HOA, spherical aberration and coma was measured by Sirius corneal topographer.Objective scatter index (OSI), modulation transfer function cut-off frequency (MTF cut-off), Strehl ratio (SR), simulated contrast visual acuity VA100 (day), VA20 (dusk) and VA9 (night) were measured via OQAS II visual quality analysis system.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of the Dalian Third People's Hospital Affiliated to Dalian Medical University (No.2019-KT-010). Written informed consent was obtained from each subject.Results:There was no significant difference in 3-month postoperative UCVA and effectiveness between the two groups ( Z=0.880, P=0.380; t=0.920, P=0.058). Patients in SPT-TransPRK group showed mild hyperopia 3 months after surgery.Preoperative, 1- and 3-month postoperative total corneal HOA was (0.47±0.18), (0.70±0.22) and (0.74±0.19)μm in SMILE group, and (0.40±0.14), (0.98±0.35) and (0.94±0.22)μm in SPT-TransPRK group respectively, showing statistically significant differences ( Fgroup=13.851, P=0.001; Ftime=29.960, P<0.001). Preoperative, 1- and 3-month postoperative spherical aberration was (-0.20±0.09), (-0.44±0.14) and (-0.44±0.15)μm in SMILE group, and (-0.20±0.10), (-0.71±0.23) and (-0.75±0.20)μm in SPT-TransPRK group respectively, showing statistically significant differences ( Fgroup=31.037, P<0.001; Ftime=48.005, P<0.001). The postoperative total corneal HOA and spherical aberration were increased in both groups compared with before surgery, with statistically significant differences (all at P<0.05). The 1- and 3-month postoperative total corneal HOA and spherical aberrations were smaller in SMILE group than in SPT-TransPRK group, and the differences were statistically significant (all at P<0.05). The 1- and 3-month postoperative coma were increased in both groups compared with before surgery, showing statistically significant differences (all at P<0.05). In SMILE group, 1-month postoperative OSI was higher and 1-month postoperative MTF cut-off, SR, and VA9 were lower than those before surgery, and 3-month postoperative OSI was higher and 3-month postoperative SR and VA9 were lower than those before surgery, showing statistically significant differences (all at P<0.05). In SPT-TransPRK group, 1-month postoperative OSI was higher and 1-month postoperative MTF cut-off, SR, VA100, VA20, and VA9 were lower than those before surgery, showing statistically significant differences (all at P<0.05). There was no significant difference in OSI, MTF cut-off, SR, VA100, VA20, and VA9 between 3 months postoperatively and before surgery in the SPT-TransPRK group (all at P>0.05). There was no significant difference in coma, OSI, MTF cut-off, SR, VA100, VA20, and VA9 between two groups (all at P>0.05). Conclusions:Both SMILE and SPT-TransPRK are effective methods for correcting myopia and they have comparable visual quality.Compared with SPT-TransPRK, corneal total HOA and spherical aberration are smaller after SMILE.
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Objective:To investigate the clinical value of spherical lens with 0.05 D intervals in optometry for small incision lenticule extraction (SMILE) in myopic eyes.Methods:A randomized controlled clinical study was conducted.Sixty patients (120 eyes) with low to moderate myopia and myopic astigmatism who underwent SMILE in the 989th Hospital of the PLA from June 2021 to February 2022 were enrolled.The patients were randomly divided into 0.05 D interval group (optometry with spherical lens at 0.05 D interval) and 0.25 D interval group (optometry with spherical lens at 0.25 D interval), with 30 cases (60 eyes) in each group.There was no significant difference in matched age, sphericity, cylindricity, and best corrected visual acuity (BCVA) (all at P>0.05). The preoperative monocular red-green balance, 1- and 3-month postoperative monocular red-green balance, uncorrected visual acuity and spherical equivalent of both groups were compared.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of the 989th Hospital of the PLA (No.WZLL-2021-034). Written informed consent was obtained from each subject before any medical examination. Results:The preoperative red-green balance rate in 0.05 D interval group was 95.00%(57/60), which was higher than 35.00%(21/60) in 0.25 D interval group, showing a statistically significant difference ( Wald χ2=17.642, P<0.001). The 1- and 3-month postoperative red-green balance rates in 0.05 D interval group were 63.33%(38/60) and 56.67%(34/60), which were higher than 23.33%(14/60) and 21.67%(13/60) in 0.25 D interval group respectively, showing statistically significant differences ( Wald χ2=9.137, P=0.003; Wald χ2=7.483, P=0.006). The 1- and 3-month postoperative visual acuity in 0.05 D interval group were -0.1(-0.1, -0.1) and -0.1(-0.1, -0.1), which were higher than 0.0(-0.1, 0.0) and -0.1(-0.1, 0.0) in 0.25 D interval group respectively, showing statistically significant differences ( Wald χ2=11.624, P=0.001; Wald χ2=12.841, P<0.001). The 1- and 3-month postoperative spherical equivalent were -0.07(-0.25, 0.13)D and -0.13(-0.25, 0.13)D in 0.05 D interval group, which were higher than -0.13(-0.38, 0.25)D and -0.13(-0.38, 0.25)D in 0.25 D interval group respectively, showing no statistically significant difference between the two groups ( Wald χ2=0.029, P=0.866; Wald χ2=0.189, P=0.664). Conclusions:Compared with spherical lens at 0.25 D interval, 0.05 D interval can improve the accuracy of preoperative and postoperative red-green balance rate and postoperative visual acuity in patients with low to moderate myopia who undergo SMILE.
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Objective:To analyze and compare the corneal higher order aberration (HOA) after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE).Methods:A non-randomized controlled study was conducted.Sixty myopic patients (60 eyes) who underwent FS-LASIK or SMILE correction at Shandong Eye Hospital from April 2018 to January 2020 were enrolled and the data from the right eye were collected for analysis.Thirty cases (30 eyes) who received FS-LASIK in FS-LASIK group and 30 cases (30 eyes) who received SMILE in SMILE group had a preoperative equivalent spherical diopter of (-5.36±1.11)D and (-4.93±1.03)D, respectively.The HOA of the 6-mm anterior surface, posterior surface, and whole cornea were measured before surgery and at 1, 3, 6, and 12 months after surgery using Pentacam.The root mean square values (μm) of total corneal HOA, spherical aberration, coma and trefoil were obtained.Differences in the above root mean square values at different time points were compared between the two groups.The study protocol adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Shandong Eye Hospital (No.SDSYKYY20180306). Written informed consent was obtained from each subject.Results:The preoperative and 1-, 3-, 6-, 12-month postoperative total HOA of the anterior corneal surface were (0.428±0.126), (0.775±0.169), (0.811±0.194), (0.759±0.214), (0.704±0.199)μm in the FS-LASIK group and (0.409±0.094), (0.656±0.148), (0.681±0.161), (0.668±0.175), (0.648±0.160)μm in the SMILE group, with a significant overall difference ( Fgroup=5.652, P=0.024; Ftime=107.169, P<0.01). Compared with SMILE group, the postoperative total HOA of anterior corneal surface and spherical aberration at different time points were increased in FS-LASIK group, showing statistically significant differences (all at P<0.05). Compared with before surgery, the postoperative total HOA of the anterior corneal surface and spherical aberration at different time points were increased in both groups, showing statistically significant differences (all at P<0.05). In the two groups, the 6- and 12-month postoperative total HOA of the anterior corneal surface were reduced in comparison with the 3-month postoperative ones of the anterior corneal surface, and the 12-month postoperative spherical aberrations of the anterior corneal surface were significantly reduced in comparison with the 1- and 3-month postoperative ones of the anterior corneal surface, showing statistically significant differences (all at P<0.05). There were significant differences in the coma and trefoil of the anterior corneal surface between before and after the operation (coma: Ftime=47.848, P<0.01; trefoil: Ftime=2.497, P=0.046). Compared with before surgery, the postoperative coma was significantly increased in the two groups (all at P<0.05). There were significant differences in total corneal HOA and spherical aberration at different postoperative time points between the two groups (total HOA: Fgroup=8.093, P=0.008; Ftime=125.019, P<0.01.spherical aberration: Fgroup=4.771, P=0.037; Ftime=34.033, P<0.01). Compared with SMILE group, the total corneal HOA and spherical aberration were significantly increased in FS-LASIK group at different postoperative time points (all at P<0.05). Compared with before surgery, postoperative total HOA of the anterior corneal surface and spherical aberration at different postoperative time points were significantly increased in both groups (all at P<0.05). In both groups, the 12-month postoperative corneal spherical aberration was significantly reduced in comparison with the 1- and 3-month postoperative ones (all at P<0.05). There was a significant difference in coma between before and after surgery ( Ftime=30.829, P<0.01). Compared with before surgery, the postoperative coma was significantly increased at different time points in both groups (all at P<0.05). Conclusions:Both FS-LASIK and SMILE increase the HOA of the anterior corneal surface and the whole cornea.Compared with FS-LASIK, SMILE introduces less HOA of the anterior corneal surface and the whole cornea as well as spherical aberrations.