Effect of small incision lenticule extraction on the treatment of myopia patients and the impact on corneal biomechanics / 国际眼科杂志(Guoji Yanke Zazhi)

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.

Clinical effect of cross positioning method for correcting low and moderate astigmatism during small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

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>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<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.

Higher-order aberrations and visual quality after incision lenticule extraction surgery with intraoperative angle kappa adjustments between small and large kappa patients: A 2-year follow-up

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.

Visual quality observation of transepithelial photorefractive keratectomy and femtosecond small incision lenticule extraction for the correction of low myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To observe the changes in corneal aberrations and the characteristics of visual quality after transepithelial photorefractive keratectomy(T-PRK)and femtosecond small incision lenticule extraction(SMILE)in the correction of low myopia.METHODS: Prospective cohort study. A total of 32 cases(32 eyes)with low myopia who underwent T-PRK surgery and 45 cases(45 eyes)of SMILE surgery at Weifang Eye Hospital from April 2021 to April 2022 were selected. The uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), spherical equivalent(SE), corneal higher-order aberrations(HOAs)and objective visual quality were compared between the two groups.RESULTS:All patients completed the surgery successfully without complications such as infection. At 3mo postoperatively, the safety index was 1.13±0.16 and 1.16±0.17(P=0.48)and the efficacy index was 1.10±0.20 and 1.15±0.18(P=0.27)in the T-PRK and SMILE groups, respectively. The percentage of UCVA(LogMAR)≤0 in the T-PRK and SMILE groups was 94% and 98%, respectively. The percentage of the residual SE within ±0.5D was 88% and 87% in the two groups, respectively. The HOAs and spherical aberration in both groups were significantly increased(P≤0.01), and the increase was not statistically significant between the two groups(P=0.31, 0.89). There was no significant change in horizontal coma, horizontal trefoil and vertical trefoil in both groups(P&#x0026;#x003E;0.05). The vertical coma in SMILE group was significantly increased(P&#x0026;#x003C;0.001), while there was no significant change in T-PRK group(P&#x0026;#x003E;0.05), and the increase was significantly greater in SMILE group than in T-PRK group(P&#x0026;#x003C;0.001). There was no significant difference in objective scattering index(OSI), modulation transfer function cut off frequency(MTFcut off), Strehl ratio(SR), visual acuity(VA)100%, VA20% and VA9% between the two groups(P&#x0026;#x003E;0.05).CONCLUSION:Both T-PRK and SMILE showed good safety, efficacy, and visual quality in correcting low myopia, while SMILE induced more vertical coma than T-PRK.

Short-term visual quality observation of femtosecond laser small incision lenticule extraction and evolution implantable collamer lens implantation in the correction of moderate myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To investigate the short-term visual quality outcomes after femtosecond laser small incision lenticule extraction(SMILE)and evolution implantable collamer lens(EVO-ICL)implantation for the correction of moderate myopia.METHODS: Prospective control study. A total of 51 cases(51 eyes)with moderate myopia who underwent SMILE or EVO-ICL implantation surgery at Weifang Eye Hospital from April 2021 to February 2022 were selected. They were divided into SMILE group(30 patients, 30 eyes)and EVO-ICL group(21 patients, 21 eyes)according to the surgical methods. The changes of visual acuity [uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA)], diopter [spherical equivalent(SE)] and related parameters of optical quality analysis system(OQAS Ⅱ)were observed before surgery and at 1wk, 1 and 3mo after surgery, and the quality of vision(QoV)questionnaire was completed.RESULTS: At 3mo after surgery, the safety index(postoperative CDVA/preoperative CDVA)of SMILE gruop and EVO-ICL group were 1.20(1.00, 1.20)and 1.20(1.00, 1.38), respectively, the efficacy index(postoperative UDVA/preoperative CDVA)were 1.00(1.00, 1.20)and 1.00(1.00, 1.20), respectively, and the percentage of SE within ±0.50D was 87% and 100%, respectively. In SMILE group, the objective scattering index(OSI)was increased after surgery, while modulation transfer function cutoff frequency(MTF cutoff), contrast visual acuity(VA)100%, and VA20% at 1wk and 1mo after surgery, and Strehl ratio(SR)and VA9% at each time point after surgery were all decreased compared with those before surgery(all P&#x0026;#x003C;0.05). The OSI, MTF cutoff, SR and VA of EVO-ICL group showed no difference at each time point after surgery compared with those before surgery(all P&#x0026;#x003E;0.05). The most common visual symptoms after SMILE and EVO-ICL implantation were visual haze and halos, respectively.CONCLUSION: Both SMILE and EVO-ICL implantation have good safety, efficacy and predictability in the short term after the correction of moderate myopia. Both groups had visual symptoms after surgery, but the overall satisfaction of patients was high. Furthermore, EVO-ICL implantation has better objective visual quality performance.

Comparison of visual quality after refractive surgery between smart pulse technology-assisted transepithelial photorefractive keratectomy of 1 050Hz ablation frequency and small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the visual quality between smart pulse technology-assisted(SPT)transepithelial photorefractive keratectomy(TransPRK)of 1 050Hz ablation frequency and small incision lenticule extraction(SMILE)for myopia and astigmatism.METHODS: A total of 138 cases(248 eyes)who received corneal refractive surgery in the Eye Hospital of Chengdu University of TCM were enrolled from July 2020 to January 2021. The patients were divided into TransPRK group(64 cases, 123 eyes)and SMILE group(74 cases, 125 eyes)according to the surgical method. The follow-up duration was 6mo. Strehl ratio(SR)and high-order aberration at 6mm pupil diameter measured by Sirius anterior segment integrated analyzer and LogMAR visual acuity were recorded at different preoperative and postoperative time points.RESULTS: The uncorrected visual acuity(UCVA)of TransPRK group was worse than SMILE group at 1wk and 1mo after surgery(all P<0.05), but UCVA was better in TransPRK group at 6mo after surgery(P<0.05). SR in TransPRK group was lower than that in SMILE group at 1wk and 1mo after surgery(all P<0.05). There was no significant difference in SR between the two groups at 3 and 6mo after surgery(P=0.968, 0.433). At 1wk after surgery, there was no significant difference in coma between the two groups(P=0.554). At 1, 3, and 6mo after surgery, coma in the TransPRK group was lower than that in SMILE group(all P<0.05). At 1wk, 1 and 3mo after surgery, the trefoil aberration in TransPRK group was higher than that in SMILE group(all P<0.05). At 6mo after surgery, there was no significant difference in trefoil aberration between the two groups(P=0.167). At 6mo after surgery, UCVA of TransPRK group and SMILE group were -0.13±0.05 and -0.11±0.08, respectively, which were better than the best corrected visual acuity(BCVA)before surgery(-0.07±0.05 and -0.07±0.05; all P<0.05). Furthermore, the SR of both groups was higher than that before surgery(all P<0.05).CONCLUSION: Both SPT-assisted TransPRK of 1 050Hz ablation frequency and SMILE can achieve better visual acuity after refractive surgery, while SMILE has better visual quality at 1wk and 1mo after surgery. However, SPT-assisted TransPRK of 1 050Hz ablation frequency has better visual acuity at 6mo after surgery than SMILE, and the coma is smaller.

Influence of different preoperative corneal curvature on the size of optical deformation area after femtosecond laser small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

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&#x003C;42.0D group(n=30), Km&#x003E;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&#x003E;0.05), and there was no significant difference in uncorrected distance visual acuity(UDVA)and subjective refraction at 6mo after operation(all P&#x003E;0.05). The diameters of the optical deformation zone in the Km&#x003C;42.0D group, Km&#x003E;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&#x003C;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&#x003C;0.05). The diameter of optical zone in the conventional curvature group was larger than that in the Km&#x003E;47.0D group(P&#x003C;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.

Changes of corneal densitometry after small incision lenticule extraction and femtosecond laser in situ keratomileusis / 国际眼科杂志(Guoji Yanke Zazhi)

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&#x003C;0.05). There was no statistical difference in the SE between the two groups at the postoperative follow-ups(P&#x003E;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&#x003C;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&#x003C;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.

Curative effect of full-femtosecond small incision lenticule extraction on the treatment of high myopia based on propensity score matching / 国际眼科杂志(Guoji Yanke Zazhi)

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&#x003C;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&#x003E;0.05).CONCLUSION: SMILE has a definite effect on patients with high myopia and is helpful to improve visual acuity.

Changes in retinal peripheral refractive status and aberrations before and after femtosecond laser-assisted laser in situ keratomileusis and small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

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&#x003E;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&#x003C;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&#x003C;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&#x003C;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.

Research progress of opaque bubble layer created in corneal stroma during femtosecond laser surgery / 国际眼科杂志(Guoji Yanke Zazhi)

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.

Changes in corneal biomechanics after small incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis evaluated by corneal visualization Scheimpflug technology / 国际眼科杂志(Guoji Yanke Zazhi)

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&#x0026;#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&#x0026;#x003C;0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P&#x0026;#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&#x0026;#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&#x0026;#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.

Correlation of intraocular pressure changes and the surgical parameters after SMILE for high myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To analyze the correlation of changes in non-contact intraocular pressure(IOPNCT)and the surgical parameters after femtosecond laser small incision lenticule extraction(SMILE)for high myopia.MOTHODS:A retrospective analysis, the clinical data of 98 patients(196 eyes)with high myopia were operated SMILE in the optometric center of Gansu Provincial Hospital from January 2018 to July 2019 were analyzed. The change of IOPNCT before and after operation was observed, and recorded the optical zone(OZ), lenticule thickness(LT), cap thickness(CT)and residual stromal thickness(RST)and the correlation with the change value of IOPNCT(△IOPNCT, △IOPNCT=IOPpreoperative-IOP postoperative at 6mo).RESULTS:After operation at 1d, 1wk, 1,3 and 6mo, the group of patients with IOPNCT(10.84±2.14,11.00±2.19,10.65±2.43,10.45±2.04,10.61±1.39mmHg)and the preoperative(16.79±1.65mmHg)comparison have a difference(P<0.001).The optical zone and lenticule thickness were positively correlated with △IOPNCT respectively(r=0.1537, 0.8161, all P<0.05). The cap thickness and residual stromal thickness were negatively correlated with △IOPNCT respectively(r=-0.8362, -0.3351, all P<0.0001). Introduce the above related factors into a multiple linear regression analysis model. The regression coefficients of variables are statistical significane. The regression equation was Y=16.189+0.227X1+0.032X2-0.083X3-0.007X4(Y=△IOPNCT, X1=OZ, X2=LT, X3=CT, X4=RST). The equation was statistically significant(F=195.704, P<0.001), and the regression model coefficient of determination R2=0.901.CONCLUSION:The intraocular pressure changes after SMILE with high myopic were correlated with optical zone, lenticule thickness, cap thickness and residual stromal thickness. The regression equation would provide reference to evaluation the real intraocular pressure after SMILE in clinic.

Influence of eye movement on precision of corneal ablation and refraction status in SMILE / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To evaluate the influence of slight eye movement during laser scanning on femtosecond laser precision of corneal ablation and postoperative refractive status in small incision lenticule extraction(SMILE). METHODS: Totally 32 patients(62 eyes)who underwent SMILE surgery in our hospital from January 2019 to March 2021 were included and divided into the movement group and the fixation group according to whether the eyeballs were slightly moved during the operation, and select patients with slightly moved monocular eyeballs for binocular pairing. The actual difference of absolute value of corneal absolute cutting error(ACE), astigmatism error(AE), absolute refractive error(ARE)and absolute visual error(AVE)was compared between the movement group and the fixation group and the two eyes of the patients with slight ocular movement in one eye at 1mo after surgery, and the surgical images were quantified to analyze the correlation between the amplitude of ocular movement and AE, and to compare the effects of the area, layer and direction of slight eye movement on ACE.RESULTS: There were no differences in all observed results between movement group and fixation group(P&#x003E;0.05). Patients with slight movement of one eye had a difference in binocular AE(0.57±0.31D vs 0.33±0.27D, P&#x003C;0.05), and the amplitude of movement was positively correlated with AE at 1mo after surgery(r=0.564, P&#x003C;0.05). There was no statistical differences in ACE at 1mo after surgery in patients with slight ocular movement in different regions(central/peripheral), layers(upper/lower lens)and direction(nasal/temporal)(all P&#x003E;0.05).CONCLUSION:The slight eye movement during laser scanning in SMILE has no significant influence on precision of corneal ablation. It mainly causes decentered ablation and the changes of corneal astigmatism, which has little effect on the spherical equivalent and visual acuity.

Research progress of visual quality after SMILE / 国际眼科杂志(Guoji Yanke Zazhi)

Femtosecond laser small incision lenticule extraction(SMILE)is one of the most advanced corneal refractive operations at present. Different from other traditional corneal refractive operations, SMILE achieves minimally invasive and valveless operation. Therefore, the evaluation of postoperative visual quality of SMILE also has its own characteristics, at present, the latest research at home and abroad has confirmed that the naked eye vision can be significantly improved and the refractive status is stable after SMILE. However, there are different understandings of the objective visual quality indexes and their influencing factors, such as higher-order aberration, modulation transfer function cut off(MTF cut off)and objective scatter index(OSI)after SMILE. This paper reviews the postoperative visual quality and its influencing factors after SMILE to provide clinical help.

Effect of different energy settings of SMILE on stage Ⅰ opaque bubble layer and visual quality / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To explore the effect of different energy parameters of femtosecond laser small incision lenticule extraction(SMILE)on stage Ⅰ opaque bubble layer(OBL)and visual quality. <p>METHODS: A retrospective analysis of the clinical data of 216 patients(432 eyes)who came to our hospital for SMILE surgery from July 2018 to December 2019. According to whether stage Ⅰ OBL occurred, they were divided into OBL group(42 eyes)and non-OBL group(390 eyes). The age, visual acuity parameters, corneal parameters, microlens parameters and energy parameters were compared between the two groups, and multivariate regression analysis was used to analyze the relationship between the difference in energy settings and the OBL of stage Ⅰ. The uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), and modulation transfer function cut-off spatial frequency(MTF_cut-off), Strehl Ratio(SR)and Objective Scattering Index(OSI)with energy parameters of 130, 135, 140, 145, and 150 nJ before and 1mo after surgery were compared. The correlation between energy parameters and stage Ⅰ OBL, UCVA, BCVA, MTF_cut-off, SR, OSI were analyzed. <p>RESULTS: Multivariate regression analysis showed that the energy setting with a difference of 5nJ did not show an association with stage Ⅰ OBL. In the different energy parameter groups, LogMAR UCVA, MTF_cut-off, and OSI at 1mo after surgery were improved compared with preoperatively(<i>P</i><0.05), and the difference between the groups were statistically significant(<i>F</i>=75.712, 15.304, 26.293, all <i>P</i><0.05). SMILE intraoperative energy parameters were negatively correlated with UCVA(<i>r</i>=-0.272), MTF_cut-off(<i>r</i>=-0.132), and OSI(<i>r</i>=-0.151)1mo after surgery(<i>P</i><0.05). <p>CONCLUSION: When using a 4.5μm dot pitch, in the usual energy range, the lower the energy, the better the postoperative visual quality, but it does not significantly affect the incidence of stage Ⅰ OBL during SMILE surgery.