| Objective:To investigate the changes of corneal epithelial thickness and corneal anterior surface aberrations after customized corneal wavefront-guided femtosecond laser-assisted in situ keratomileusis(FS-LASIK)and analyze the correlation between corneal epithelial thickening and changes of corneal anterior surface higher-order aberrations(HOA).Methods:This is a prospective study.Patients who underwent customized corneal wavefrontguided FS-LASIK from January to February 2021 were enrolled The clinical data were collected preoperatively and 1 day,3 days,10 days,1 month,3 months and 6 months postoperatively.The patients’ visual acuity,refraction,corneal curvature,kappa angle,corneal epithelial thickness and corneal anterior surface HOA were recorded in detail.Firstly,the trend of corneal thickening was analyzed.And the factors affecting corneal epithelial thickening were analyzed according to the patients’ SE,age and gender.Next,the trends of corneal total root mean square higher-order aberrations(RMS HOA),peak-to-valley ratio(P-V),vertical coma,horizontal coma,horizontal trefoil,vertical trefoil,coma,trefoil and spherical aberrations on the corneal anterior surface were analyzed.And the factors affecting the HOA were analyzed according to the patients’ SE,age and gender also.Finally,Pearson correlation analysis was used to analyze the correlation between an amount of changes in corneal epithelial thickness in 17 regions and corneal anterior surface coma at 10 days to 1 month postoperatively.Results:According to the inclusion and exclusion criteria,clinical data of 26 patients(52 eyes)who underwent customized FS-LASIK were collected in this study.The baseline data of the patients were not specific.The mean age of the patients was 26.57±6.28 years old.The mean uncorrected distance visual acuity(UDVA)logMAR was 1.12±0.21,the mean corrected distance visual acuity(CDVA)logMAR was 0.02±0.04 at preoperatively.The mean sphere was-4.83±1.70D,the mean cylinder was-1.00±0.67D,the mean spherical equivalent(SE)was-5.23±1.70D at preoperatively.And the mean central corneal thickness(CCT)was 549.38±23.59 μm at preoperatively.The mean UDVA LogMAR was-0.10±0.06,the mean sphere was-0.13±0.44D,the mean cylinder was-0.34±0.24D,and the mean SE was-0.28±0.43D at 6 months postoperatively.1.Patterns of corneal epithelial thickness changes after customized FS-LASIKAt 6 months postoperatively,the central and paracentral corneal epithelium were thickened by 3.43±4.80μm and 4.39±4.59μm respectively,and the midperipheral area was thinned by 2.14±3.43μm,with a "negative meniscus" like epithelial thickening pattern.The epithelium in the paracentral area tended to thicken,then thinned and then thickened again,and stabilized at 6 months postoperatively.While the epithelium in the nasal,inferior nasal,inferior and temporal inferior regions thickened more,by 6.86±4.42μm,7.14±4.87μm,6.86±4.20μm and 4.64±3.88μm respectively.The epithelium in the midperipheral area showed a tendency to thin,with the superior,inferior nasal,inferior and inferior temporal epithelium thinned more,by 3.50±4.42μm,-2.21±3.75μm,-2.14±2.93μm and-2.14±2.48μm respectively.Because the central and paracentral corneal epithelium thickened more,we analyzed the effects of age,gender and refraction on the epithelial thickness changes in these areas.Age and gender were not related to epithelial thickness changes.But preoperative SE was related to epithelial thickness changes.At 3 days postoperatively,the thickness of inferior temporal epithelium in the low degree group was 0.83±1.17μm,which was significantly less than moderate degree group 2.77±1.30μm and high degree group 4.43±3.91μm(P=0.012,0.035<0.05).However,there was no significant difference between the moderate and high degree groups(P=0.351>0.05).At 10 days postoperatively,the amount of nasal epithelial thickness changes was 1.00±2.19μm in the low degree group,3.54±2.26μm in the moderate degree group and 5.57±3.51μm in the high degree group;the amount of inferior epithelial thickness changes was 1.50±2.17μm in the low degree group,3.92± 1.66μm in the moderate degree group and 6.00±3.61 μm in the high degree group;the amount of inferior nasal epithelial thickness changes was 1.67± 1.97μm in the low degree group,3.69±2.14μm in the moderate degree group and 6.14±3.63μm in the high degree group;the amount of thickness changes in the inferior temporal epithelium was 0.17±2.23 μm in the low degree group,2.54±1.67μm in the moderate degree group and 4.00±3.70μm in the high degree group.The inferior epithelial thickness of low degree group was significantly less than moderate and high degree groups(P=0.035,0.037<0.05),but there was no significant difference between moderate and high degree groups(P=0.174>0.05).The nasal,inferior nasal,inferior temporal epithelial thickness of low degree group were significantly less than high degree group(P=0.017,0.016,0.034<0.05),but there was no significant difference between moderate and high degree groups(P=0.07,0.135,0.071>0.05)or low and moderate degree groups(P=0.141,0.074,0.255>0.05).2.Patterns of corneal anterior surface HOA changes after customized FS-LASIKPostoperative HOA on the anterior corneal surface generally decreased,but changed with time.RMS HOA increased by 0.10±0.13μm and P-V increased by 0.53±0.79μm at 6 months postoperatively.Vertical coma decreased by 0.04±0.15μm,horizontal coma increased by 0.03±0.10μm,coma decreased by 0.01 ±0.16μm at 6 months postoperatively.Horizontal trefoil decreased by 0.01 ±0.08μm,vertical trefoil decreased by 0.04±0.12μm,trefoil decreased by 0.04±0.12 μm at 6 months postoperatively.Spherical aberrations increased 0.13±0.08μm at 6 months postoperatively.Age mainly affected the vertical coma.In the ≤20 years old group,changes of vertical coma were-0.009±0.103μm at 10 days,-0.013±0.131μm at 1 month and-0.021±0.079μm at 3 months postoperatively.In the 20～30 years old group,changes of vertical coma were-0.017±0.101μm at 10 days,-0.022±0.104μm at 1 month and-0.003±0.116μm at 3 months postoperatively.In the ≥30 years old group,changes of vertical coma were-0.183±0.135μm 10 days,-0.195±0.146μm 1 month,-0.164±0.111μm at 3 months postoperatively.The changes of vertical coma in the groups of ≤20 years old and 20～30 years old were significant less than the group of ≥30 years old(P=0.012,0.011,0.022<0.05)at 10 days,1 month and 3 months postoperatively.However,there was no significant difference between the groups of 20～30 years old and ≥30 years old(P=0.892,0.583,0.766>0.05).Gender mainly affects the vertical trefoil.The changes of vertical trefoil were-0.090±0.124μm for the male group and 0.026±0.106μm for the female group at 1 day postoperatively,-0.095±0.107μm for the male group and 0.016±0.102μm for the female group at 3 days postoperatively,-0.213±0.638μm for the male group and 0.018±0.101μm for the female group at 10 days postoperatively.The changes of vertical trefoil were-0.102±0.095μm in the male group and 0.017±0.089μm in the female group at 1 month postoperatively,-0.130±0.099μm in the male group and-0.002±0.099μm in the female group at 3 months postoperatively,-0.137±0.091μm in the male group and 0.004±0.108μm in the female group at 6 months postoperatively.The reduction of vertical trefoil in the male group were significantly more than the female group(P=0.023,0.018,0.006,0.005,0.010,0.013<0.05).There was no significant difference between preoperative SE and the changes of corneal HOA(P>0.05).3.Correlation between the changes of corneal epithelial thickness and corneal coma after customized FS-LASIKWe did statistical analysis using the changes of corneal epithelial thickness and vertical coma,horizontal coma,and coma at 10 days versus 1 month postoperatively.The changes of the central area were correlated with the changes of vertical coma(P=0.027<0.05),the changes of epithelial thickness in the central,paracentral and midperipheral areas were correlated with the changes of horizontal coma(P=0.0002,0.001,0.003<0.01)and the variation of coma(P=0.0003,0.007,0.025<0.05).There was a correlation between the difference of the central and paracentral areas epithelial thickness change and the changes of vertical coma,and the changes of coma(P=0.005,0.009<0.01).There was no correlation between the difference of the epithelial thickness between the paracentral and midperipheral areas and the variation of vertical coma,horizontal coma,coma(P=0.823,0.805,0.657>0.05).The changes of epithelial thickness in each region of the paracentral area(P=0.827,0.438,0.130,0.450,0.059,0.079,0.101,0.200>0.05)and midperipheral area(P=0.224,0.299,0.674,0.703,0.110,0.565,0.214,0.354>0.05)did not correlate with the changes of vertical coma.The changes of epithelial thickness in all regions of the paracentral area(P=0.035,0.002,0.009,0.002,0.003,0.002,0.001,0.005<0.05)and midperipheral area(P=0.018,0.030,0.005,0.006,0.044,0.045,0.024<0.05)correlated with the changes of horizontal coma.There were correlations between the epithelial thickness changes in each region of the paracentral areas and the change of coma(P=0.049,0.023,0.036,0.003,0.004,0.002,0.016<0.05).But there were no correlation with the changes of epithelial thickness changes in each region of the midperipheral region and the changes of coma(P=0.063,0.077,0.371,0.144,0.198,0.056,0.081>0.05).The diagonal epithelial thickness differences in the paracentral and midperipheral areas did not correlate with the changes of vertical coma(P=0.080,0.235,0.983,0.771,0.784,0.870,0.359,0.556>0.05),horizontal coma(P=0.466,0.927,0.686,0.258,0.867,0.611,0.382,0.929>0.05)or coma(P=0.075,0.331,0.574,0.709,0.679,0.952,0.226,0.595>0.05).Conclusions:For the first time,we observed the trends of corneal epithelial thickness in various regions and HOA in the early postoperative period after customized corneal wavefrontguided FS-LASIK with the Amaris 750S excimer laser platform.We found that the corneal epithelial thickness in the central and paracentral areas increased and the epithelial thickness in the midperipheral area thinned.Preoperative SE affected corneal epithelial thickness changes.Corneal HOA decreased in the early postoperative period.However,coma and trefoil increased with time,but they were smaller than those before the operation.These results demonstrated the advantages of customized FS-LASIK and revealed that gender and age all affected corneal HO A changes.In addition,the present study innovatively analyzed the correlation between the changes of the different regions corneal epithelial thickness and corneal coma.We found that the changes of epithelial thickness in the central,paracentral and midperipheral areas were related to corneal coma,horizontal coma and vertical coma changes.It is suggested that postoperative visual quality of customized FS-LASIK may be influenced by changes of corneal epithelial thickness. |
