Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism

AIM： To compare and calculate the 3-year refractive results, higher-order aberrations （HOAs）, contrast sensitivity （CS） and dry eye parameters after small incision lenticule extraction （SMILE） and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis （FS-LASIK） for correction of high myopia and myopic astigmatism. METHODS： In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent （SE） of -8.11±1.09 diopters （D） received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser （Carl Zeiss Meditec, Jena, Germany） for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index （OSDI） and tear break-up time （TBUT） were evaluated during a 3-year follow-up. RESULTS： The difference of uncorrected distance visual acuity （UDVA） postoperatively was achieved at lmo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant （t=-1.59, P=-0.13）. The postoperative change of SE was 0.89 D in the FS-LASIK group （t=5.76, P=0.00）, and 0.14 D in the SMILE group （t=-0.54, P=0.59） from lmo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group （P=0.00）, but the coma root mean square （RMS） was higher in the SMILE group （0.59±0.26） than in the FS-LASIK group （0.29±0.14, P=0.00）. The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at Imo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. CONCLUSION： Both SMILE and wavefront-guided FS- LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better control of early postoperative dry eye as compared to FS-LASIK.

Dry eye and corneal sensitivity after small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis:a Meta-analysis

AIM：To assess the corneal sensitivity and the incidences of dry eye after small incision lenticule extraction（SMILE） and femtosecond laser-assisted in situ keratomileusis（FSLASIK）.METHODS：The Meta-analysis was performed using Rev Man 5.3.We searched on Pub Med from inception to March 2016.Summary weighted mean difference（WMD） and 95% confidence intervals（CIs） were used to analyze the datum.Random-effects or fixed-effects models were chosen up to between-study heterogeneity.The main outcomes were composed of the Ocular Surface Disease Index（OSDI） scores,tear film break-up time（TBUT）,Schirmer Test and corneal sensitivity.RESULTS：Eight eligible studies including 772 eyes（386 in SMILE group and 386 in FS-LASIK group） were identified.The parameters have no significiant difference heterogeneity between SMILE and FS-LASIK group preoperatively.There were significant differences between the two groups in OSDI scores at one and three months postoperatively,in TBUT at one and three months postoperatively,in corneal sensitivity at one week,about one month and three months postoperatively.However,there was no significant difference observed in Schirmer Test at the follow-up periods.CONCLUSION：Compare to FS-LASIK,dry eye and the corneal sensitivity recover better in the SMILE group,in first three months after the surgery.

Comparison of the flaps made by femtosecond laser and automated keratomes for sub-bowman keratomileusis

Background Thin-flap laser in situ keratomileusis （LASIK） is the new trend of refractive error correction surgery, the formation of corneal flap is crucial for a success of LASIK surgery. This study aimed to assess and compare the variations of LASIK flap created by the IntraLase femtosecond laser, Moria One Use-Plus SBK and Moria M2 Single-Use 90 pm- head microkeratome using Anterior segment optical coherence tomography （Visante OCT）. Methods One hundred and sixty-one eyes of 81 consecutive patients were enrolled in this prospective study and randomly divided into three groups depending on the flap creation method： flap creation with the the IntraLase femtosecond laser （IntraLase group, 59 eyes）, flap creation with the Moria One Use-Plus SBK （SBK group, 44 eyes）, and flap creation with the Moria M2 Single-Use 90 pm-head microkeratome （M2SU90 group, 58 eyes）. The nominal flap thickness was 110 m for all patients and for the three devices. One month after surgery, Visante OCT was used to measure the flap thickness at 20 locations on each cornea and the results were assessed for uniformity, regularity, and accuracy. Results At 1 month after surgery, the mean central flap thickness was （111±3） pm in the IntraLase group, （114±8） pm in the SBK group, and （118±13） pm in the M2SU90 group respectively. The flaps in the IntraLase group and the SBK group were more regular, showing an almost planar configuration, than the meniscus-shaped flaps in the M2SU90 group. The maximum deviation from the intended flap thickness （110 pm） was 6 pm in the IntraLase group, 10 pm in the SBK group, and 20 pm in the M2SU90 group respectively. A difference greater than 20 pm was observed in 0.42% of measurements in the IntraLase group; 2.95% of the measurements in the SBK group and 21.12% of measurements in the M2SU90 group. Conclusions The flaps created by the IntraLase femtosecond laser and Moria One Use-Plus SBK are more uniform; more regular, and more accurate than those created by the Moria M2 Single-Use 90 pm-head microkeratome. The first two methods can make precise flaps for Sub-Bowman Keratomileusis.

Comparison of early changes in ocular surface markers and tear inflammatory mediators after femtosecond lenticule extraction and FS-LASIK

AIM:To compare the short-term impacts of femtosecond lenticule extraction(FLEx)and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)on ocular surface measures and tear inflammatory mediators.METHODS:This prospective comparative nonrandomized clinical study comprised 75 eyes(75 patients).Totally 20 male and 15 female patients(age 21.62±3.25 y)with 35 eyes underwent FLEx,and 26 male and 14 female patients(age 20.18±3.59 y)with 40 eyes underwent FS-LASIK.Central corneal sensitivity,noninvasive tear breakup time,corneal fluorescein staining,Schirmer I test,tear meniscus height,and ocular surface disease index were evaluated in all patients.Tear concentrations of nerve growth factor(NGF),interleukin-1α(IL-1α),transforming growth factor-β1(TGF-β1),tumor necrosis factor-α(TNF-α),interferon-γ(IFN-γ),and matrix metalloproteinase-9(MMP-9)were assessed by multiplex antibody microarray.All measurements were performed preoperatively,and 1 d,1 wk,and 1 mo postoperatively.RESULTS:Patients who underwent FLEx exhibited a more moderate reduction in central corneal sensation and less corneal fluorescein staining than those in the FS-LASIK group 1 wk after the procedure(P<0.01).NGF was significantly higher 1 d and 1 wk after surgery in the FS-LASIK group than in the FLEx group(P<0.01).By contrast,compared to those in the FLEx group,higher postoperative values and slower recovery of tear TGF-β1,IL-1α,and TNF-αconcentrations were observed in the FS-LASIK group(P<0.01).Tear concentrations of NGF,TGF-β1,TNF-α,and IL-1αwere correlated with ocular surface changes after FLEx or FS-LASIK surgery.CONCLUSION:There is less early ocular surface disruption and a reduced inflammatory response after FLEx than after FS-LASIK.NGF,TGF-β1,TNF-α,and IL-1αmay contribute to the process of ocular surface recovery.

Femtosecond laser corneal refractive surgery for the correction of high myopic anisometropic amblyopia in juveniles

AIM： To evaluate the effects of femtosecond laser-assisted in situ keratomileusis（FS-LASIK） and small-incision lenticule extraction（SMILE） to correct high myopic anisometropic amblyopia in juvenile patients. METHODS： From November 2013 to January 2015, 33 amblyopic patients with high myopic anisometropic amblyopia were studied. FS-LASIK（30 eyes） or SMILE（3 eyes） was performed in the amblyopic eyes. Visual acuity, refraction, contrast sensitivity, stereoacuity and complications were evaluated. Patients completed followup examinations at 3 d, 1 mo, 3 mo and the last follow-up time（mean 8.17±3.23 mo） after surgery. RESULTS： The mean age at surgery was 9.04±3.04 y（range 6-16 y）. The mean spherical equivalent in the amblyopic eyes was significantly decreased from-10.00±2.39 D preoperatively to-0.06±1.06 D at 1 mo,-0.19±1.33 D at 3 mo and-0.60±1.43 D at approximately 8 mo postoperatively（P〈0.05 for all）. The mean myopic anisometropia was significantly decreased from-9.45±2.33 D preoperatively to ＋0.37±1.48 D at 1 mo,-0.46±1.47 D at 3 mo and-0.09±1.83 D at approximately 8 mo（P〈0.05 for all）. The logarithm of the minimum angle of resolution（log MAR） for uncorrected and corrected distance visual acuity（UDVA and CDVA, respectively） of the amblyopic eye improved from 1.74±0.35 and 0.98±0.63 preoperatively to 0.45±0.31 and 0.41±0.33 at approximately 8 mo after surgery, respectively. The logM AR CDVA at 3 d, 1, 3 and 8 mo postoperatively improved by means of 1.42, 2.22, 2.96, and 4.39 lines, and a gain of more than two lines accounted for 45%, 50%, 74% and 86% of all patients, respectively. The contrast sensitivity of both amblyopic eyes and dominant eyes at 0.5, 2, 8 cycles perdegree was significantly improved postoperatively（P〈0.05 for all）. Of the 33 pediatric patients, no patients had near stereopsis preoperatively and seven patients（21.2%） recovered near stereopsis（400″ to 60″） at approximately 8 mo after surgery. No intraoperative or postoperative complications occurred in any patient.CONCLUSION： FS-LASIK or SMILE can be promising alternative methods to correct high myopic anisometropic amblyopia in juvenile patients who have failed with traditional approaches.

Changes in corneal biomechanics and posterior corneal surface elevation after FS-LASIK

AIM:To investigate the changes in corneal biomechanics and posterior corneal surface elevation after femtosecond laser-assisted in situ keratomileusis(FS-LASIK).METHODS:Totally 197 eyes of 100 patients who underwent the FS-LASIK from April 2022 to November 2022 were included.They were divided into three groups according to the ratio of residual corneal stroma thickness/corneal thickness(RCST/CT):Group I(50%≤RCST/CT<55%,63 eyes of 32 patients),Group II(55%≤RCST/CT<60%,67 eyes of 34 patients),and Group III(RCST/CT≥60%,67 eyes of 34 patients).The intraocular pressure(IOP),corneal compensated IOP(IOPcc),corneal hysteresis(CH)and corneal resistance factor(CRF)were measured immediately,1,and 3mo postoperatively by ocular response analyzer(ORA)and the posterior elevation difference(PED)was measured by Pentacam.RESULTS:After operation,IOP,CH,CRF,and PED were statistically different among the three groups(F=12.99,31.148,23.998,all P<0.0001).There was no statistically significant difference in IOPcc among the three groups(F=0.603,P>0.05).The IOP,IOPcc,CH,and CRF were statistical changed after surgery(F=699.635,104.125,308.474,640.145,all P<0.0001).The PED of Group I was significantly higher than that of Group II(P<0.05),and Group II was significantly higher than that of Group III(P<0.05).The PED value of 3mo after surgery decreased in each group compared with 1mo after surgery,but there was no statistical difference(Group I:t=0.82,P=0.41;Group II:t=0.17,P=0.87;Group III:t=1.35,P=0.18).The correlation analysis of corneal biomechanical parameter changes with PED at 1mo and 3mo after surgery showed thatΔIOP,ΔIOPcc,ΔCH,andΔCRF were not correlated with PED value in three groups(P>0.05).CONCLUSION:The smaller the RCST/CT,the greater effect on corneal biomechanics and posterior surface elevation.There is no correlation between changes in corneal biomechanics and posterior corneal surface elevation in the range of RCST/CT≥50%.

Early visual function outcomes of topography-guided FS-LASIK and SMILE in treatment of myopia and myopic astigmatism

AIM: To compare the quality outcomes of vision at early phase after topography-guided femtosecond laser-assisted in situ keratomileusis(FS-LASIK-CV) and small incision lenticule extraction(SMILE) in treatment of myopia and myopic astigmatism.METHODS: Retrospective comparative analysis of 49 patients that underwent FS-LASIK(n=23) or SMILE(n=26) procedure for myopia and myopic astigmatism between April and September in 2019. Pre-and postoperative uncorrected visual acuity(UCVA), spherical equivalent refraction(SEQ), cylindrical refraction, contrast sensitivity function(CSF), and corneal higher-order aberrations(HOAs) were evaluated. Independent t-test was used for inter-group comparison, while repeated measures ANOVA was used to analyze changes at different time points. RESULTS: In both groups, 100% of the eyes obtained a UCVA of 20/20 or better at 1 wk, 1, and 3 mo postoperatively. At 1 d and 3 mo postoperatively, UCVA was better in FS-LASIKCV group than in SMILE group. At 1 wk postoperatively, SEQ was lower in SMILE group than in FS-LASIK-CV group(P=0.006). At 3 mo postoperatively, the SEQ reached target refraction in both groups. The residual astigmatism was reduced in both groups without intergroup difference(P>0.05). At 3 mo postoperatively, the spherical aberration and coma under 6 mm pupil size were higher than preoperative levels in both groups(P<0.05). However, the increase in the corneal HOAs in the FS-LASIK-CV group was less than the SMILE group(P<0.05). At 3 mo postoperatively, the log CS were better than preoperative levels under scotopic conditions without glare and scotopic conditions with glare in both groups(P<0.05). At 1 and 3 mo postoperatively, under scotopic conditions without glare and scotopic conditions with glare, FS-LASIK-CV group showed more improvement in log CS at two spatial frequencies(12.0 c/d and 18.0 c/d;P<0.05).CONCLUSION: Both FS-LASIK-CV and SMILE demonstrate to be safe, effective, and predictable in treatment of myopia and myopic astigmatism. Early postoperative improvement in UCVA and CSF at high spatial frequency under scotopic conditions were better after FS-LASIK-CV than SMILE.