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AIM:To evaluate corrective effect and stability of corneal morphology in patients with moderate to high myopia after 2a treatment of femtosecond laser assisted laser in situ keratomileusis(FS-LASIK)Xtra.METHODS:Retrospective case-control study. A total of 30 cases(58 eyes)Patients with moderate to high myopia combined with astigmatism who planned to undergo refractive surgery in our hospital from August 2019 to August 2020 were included, and different types of surgery were performed respectively based on the relevant index of keratoconus screening in the preoperative corneal topography. They were divided into FS-LASIK group and Xtra group, with 15 cases(29 eyes)in each group. Uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA), spherical equivalent(SE)and the corneal curvature of the anterior and posterior surfaces of different diameters(3, 5 and 7 mm)measured by Sirius three-dimensional corneal topography were observed preoperatively and 3 mo, 1 and 2 a postoperatively.RESULTS: The UCVA of the two groups of patients at different time points after surgery was significantly increased compared with preoperatively(both P<0.01), and there was no difference in UCVA and SE between the two groups(P>0.05). After 2 a postoperatively, residual astigmatism was -0.25-0 D in 25 eyes(86%)of the FS-LASIK Xtra group and 24 eyes(83%)of the FS-LASIK group. The actual corrected SE and expected corrected SE of both groups were positively correlated(both P<0.05). There were differences in corneal curvature on the surface of different diameter areas(3, 5, and 7 mm)between the two groups at 3 mo, 1, and 2 a postoperatively compared with preoperatively. After 1 and 2 a postoperatively, the corneal posterior surface curvature of the FS-LASIK Xtra group with corneal diameter of 3 and 5 mm was higher than that of the FS-LASIK group(P<0.05).CONCLUSIONS:FS-LASIK Xtra has good safety, efficacy and predictability in correcting patients with moderate to high myopia.
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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>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<0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P>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<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<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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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 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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Objective:To investigate and compare the changes of modulation transfer function (MTF) after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK).Methods:A cohort study was conducted.One hundred and two myopic patients (102 eyes) who underwent SMILE and FS-LASIK in Tianjin Eye Hospital from December 2015 to June 2016 were enrolled and divided into SMILE group with 53 eyes and FS-LASIK group with 49 eyes according to different surgical methods.The ocular aberrations and corneal morphology of all patients were measured by the Hartman-Shack wave-front analyzer and Pentacam topography before surgery and 1, 3 and 6 months postoperatively.MTF of optic system was calculated and analyzed.The changes of MTF values were compared between the two groups at different time points under different spatial frequencies, after removal of low-order aberrations at postoperative 6 months, and after removal of vertical coma aberration, horizontal coma aberration and spherical aberration in the SMILE group at postoperative 6 months.The study protocol complied with the Declaration of Helsinki and was approved by an Ethics Committee of Tianjin Eye Hospital (No.TJYYLL-2014-17). Written informed consent was obtained from each patient before surgery.Results:Compared with the preoperative MTF, there were significant increases in postoperative 1-, 3- and 6-month MTF at all spatial frequencies in the SMILE group and FS-LASIK group (all at P<0.05). MTF values at all spatial frequencies in the SMILE group were significantly higher than those in the FS-LASIK group at 1, 3, and 6 months after surgery (all at P<0.05), except at 55 c/d and 60 c/d at 6 months postoperatively.The postoperative 6-month MTF values at all spatial frequencies without low-order aberration were higher in the SMILE group than those in the FS-LASIK group, showing significant differences between the two groups (all at P<0.05). In the SMILE group, the postoperative 6-month MTF values at 1 c/d spatial frequency without the horizontal coma aberration and spherical aberration were significantly higher than the preoperative MTF values (both at P<0.01); the postoperative 6-month MTF values at 1 c/d and 3 c/d spatial frequency without vertical coma aberration were significantly higher than the preoperative MTF values (both at P<0.05), and there were no statistically significant differences between the postoperative 6-month MTF values at the other spatial frequencies with and without single high-order aberrations (all at P>0.05). Conclusions:Optic quality has been obviously improved after SMILE and FS-LASIK, and the SMILE is superior to FS-LASIK in the MTF value.
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Objective To compare the early change of posterior corneal elevation with femtosecond laser assisted laser in situ keratomileusis (FS-LASIK) and sub-Bowman keratomileusis (SBK) by Oculyzer and analyze the related factors after FS-LASIK.Methods A longitudinal observational study was designed.Ninety-one eyes of 46 patients with myopia or myopic astigmatism in the First Affiliated Hospital of Anhui Medical University from January to April in 2016 were divided into FS-LASIK group (53 eyes of 27 patients),SBK group (38 eyes of 19 patients)according to the patients' wishes and each part of corneal elevation change values were explored after FS-LASIK and SBK surgeries.The posterior corneal elevation was measured at twenty-seven measuring points along the central,paracentral,midperipheral and peripheral zone (vertex and 1,2 and 3 mm radius) using Oculyzer preoperatively,l day,7 days and 1 month postoperatively,respectively.Written informed consent was obtained from each patient before the surgery.Results In the FS-LASIK group,the posterior corneal elevation difference values in the central zone were (-0.924± 1.859),(-1.151 ± 1.586) and (-0.940 ± 1.994) μm 1 day,7 days and 1 month postoperatively,respectively.In the periphery zone,the elevation difference values were (1.046 ± 1.667),(1.172 ± 1.566) and (1.023±1.622)μm.In the paracentral and midperipheral zone,the cornea displayed slightly backward or forward shift.In SBK group,the posterior corneal elevation difference values of the ve,ex were (-0.684 ± 1.454),(-1.053 ±1.723) and (-0.553 ± 1.572) μm 1 day,7 days and 1 month after operation,respectively.In the paracentral and midperipheral zone displayed the same trend with FS-LASIK group,and in the periphery,the values were (1.207 ±1.317),(1.327 ± 1.529) and (1.208 ± 1.415) μm.There were no statistically significant differences in posterior corneal elevation between the two surgery modes among the three time points (all at P ＞ O.05).At 1 month postoperatively,only two independent variables,which were spherical equivalent (SE) and ablation depth (AD)entered the regression in the central and paracentral zones.Independent variables,such as central thinnest corneal thickness (TCT),SE,AD,residual bed thickness (RBT) and the ratio of AD and TCT (AD/TCT) did not enter the regression in other two areas.Conclusions The posterior corneal elevation in the central 6 mm area shows tiny change in the early stage and the variation is larger 7 days after operation in the two groups,but it does not result in keratectasia.With the increase of SE and AD,the posterior corneal elevation is more likely to be affected.
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Objective This study was to study the effect of 0.1％ and 0.3％ sodium hyaluronic ophthalmic solution on tear film stability and visual quality of dry eye patients after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).Methods A prospective randomly controlled study was designed.Pre-surgery normal patients were evaluated again at 1 week after FS-LASIK,60 mild and severe dry eye patients were enrolled from April 2016 to April 2017 in Tianjin Medical University Eye Hospital.Then 0.1％ and 0.3％ sodium hyaluronate were randomly given in each dry eye group.Ocular surface disease index (OSDI),optical quality analysis system Ⅱ(OQAS Ⅱ),Keratography 5M and corneal staining were performed before operation,1 week (before instillation and 15,30,60,120 and 180 minutes after instillation),1 month and 3 months after operation.This study was approved by the Ethic Committee of Tianjin Medical University Eye Hospital (2015KY-04).Informed consent was obtained from all subjects after explanation of the nature and possible consequence of the study.Results The 0.3％ sodium hyaluronate group was better than 0.1％ sodium hyaluronate group in alleviating OSDI score and cornea staining at 3 months in the mild dry eye group (Fgroup =10.913,P =0.003;P =0.027).Compared with the before operation,the objective scatter index(OSI) was increased at 1 week before instillation and many different time points after instillation in both 0.1％ sodium hyaluronate group and 0.3％ sodium hyaluronate group,with significant differences between them (all at P＜0.05),there was no statistically significant difference in OSI at 1 month and 3 months after surgery compared with before surgery in both 0.1％ and 0.3％ sodium hyaluronatc group.In 0.1％ sodium hyaluronic group and 0.3％ sodium hyaluronic group,the mean value of total OSI at 1 week after surgery were siginifcantly higher than that before surgery (P=0.046,0.060).In 0.1％ sodium hyaluronate group,the mean values of total OSI at various time points after instillation were not statistically different from that before surgery (all at P＞0.05),total OSI at 1 month and 3 months after operation were higher than that before surgery (P =0.047,0.017);In 0.3％ sodium hyaluronic group,the mean value of total OSI at 15,30,60 and 120 minutes after instillation were significantly higher than that before surgery (all at P＜0.05),and compared with the total OSI before surgery,no statistical differences were found at 1 month and 3 months after operation (P =0.046,0.667).Significant differences were found in NIBUT avg among different time points in the mild dry eye patients (Ftime =2.290,P =0.022).In 0.1％ sodium hyaluronic group and 0.3％ sodium hyaluronic group,the NIBUT avg at 1 week after surgery were significantly lower than that before operation (both at P＜0.05).Compared with the before operation,no significant differences were found at the following 3 hours after instillation in 0.1％ sodium hyaluronic group (all at P＞0.05).In 0.3％ sodium hyaluronic group,the NIBUT avg at 60,120 and 180 minutes after instillation were significantly lower than that before surgery (P=0.040,0.047,0.041),and NIBUT avg at 3 months after operation was significantly lower than that before surgery (P =0.044).Conclusions The 0.3％ sodium hyaluronic is better than 0.1％ sodium hyaluronic in alleviating the OSDI score and cornea staining on the mild dry eye post FS-LASIK,and the tear film stability and related visual quality fluctuated over time after the application of 0.3％ sodium hyaluronic.
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Background Small incision lenticule extraction (SMILE) was a new procedure which is miniinvasion and flapless,but few attentions were paid to the visual quality after SMILE.To understand the changes of intraocular straylight after SMILE is of important significance for the assession of the visual quality after the procedure.Objective This study was to compare the characteristic of straylight between SMILE and femtosecond laser assisted laser in situ keratomileusis (FS-LAISK) after surgery.Methods A retrospective study was designed.Written informed consent was obtained from each patient prior to accepting the surgery.One hundred and twenty-seven eyes of 68 patients with myopia and myopic astigmatism were included in Tianjin Eye Hospital from January 2011 to July 2013.SMILE was performed on 64 eyes of 35 patients and FS-LASIK was carried out in 63 eyes of 33 patients at the same period.Stray light was detected with C-Quant stray light meter before and 1 week,1 month and 6 months after surgery.The changes of stray light values following the surgery were compared between the two groups,and the correlations between postoperative stray light values with operative parameters were analyzed.Results The mean stray light values were (1.03 ±0.19)D and (0.95±0.16)D at 1 week and 1 month after surgery,which were higher than (0.88 ±0.18)D at preoperation in the FS-LASIK group (P =0.000,0.012).The stray light values were (0.98±0.16),(0.95±0.14) and (0.94±0.16)D at 1 week,1 month or 6 months after surgery,and no statistically significant differences were found in comparison with (0.91 ±0.15)D in preoperation in the SMILE group (all at P＞0.05).No significant intergroup difference was seen in the stray light values (Fgroup =0.077,P=0.781).The stray light differences of various time points after surgery and before surgery were increased in the FS-LASIK group compared with SMILE group (Fgroup =14.798,P＜0.001),with the significant difference in postoperative 1 week between the two groups (P＜0.01).The negative correlations were found between stray light values at 1 week,1 month and 6 months after SMILE with the lenticule thickness/central corneal thickness (CCT) (R2=0.123,0.145,0.098,all at P＜0.05) or between stray light change.Conclusions Intraocular stray light appears less change in operative eyes after SMILE.However,intraocular stray light increases in the eyes received FS-LASIK,especially at early stage after operation.The stray light shifts return to normal with the lapse of postoperative time.