| Purpose: The purpose of this study is to investigate the longitudinal changes in corneal thickness in different regions and its relationship with diopter after small incision lenticule extraction(SMILE)and femtosecond-assisted laser in situ keratomileusis(FS-LASIK)surgery.Methods: Retrospective study.Part 1:Eighty-six subjects(146 eyes)were included from June 2014 to January 2015 in Tianjin Eyel Hospital,who underwent corneal refractive surgery including 60 cases of SMILE group(104 eyes)and 26 cases(42eyes)of FS-LASIK group.The corneal thickness(CT)were measured pre-operatively and post-operatively on day 1,week 1,and months 1,3,6.Part 2: Selected 8 patients(16 eyes)who underwent SMILE in Tianjin Eyel Hospital from August 2011 to March 2012.The corneal thickness were measured pre-operatively and post-operatively on day 1,week 1,months 1,3,6 and years 5.The deviation of actual corneal thickness measured at the thinnest location from the theoretically derived thickness at the same area and defined it as △′CT.The change in corneal thickness(△CT),which was derived from the difference of the measured CT at first day after operation and the CT at postoperative period in the same region over the cornea.The comparions between two groups were MANOVA of repeated measuring.The association between different parameters with Pearson or Spearman rank correlation coefficients.P less than 0.05 was considered statistically significant.Results: 1.In both SMILE and FS-LASIK groups,the corneal thickness in all three regions at week 1 were thinner than day 1(SMILE:p≤0.002;FS-LASIK:p<0.001).The FS-LASIK group showed greater change than SMILE(p<0.001).Both groups showed an increase in corneal thickness from 1 month to 3 months(SMILE:p<0.001;FS-LASIK:p<0.001);2.The corneal thickness was comparable between 3-and 6-month follow-up after SMILE(p>0.05)whereas the central and the external annular region had a significant linear increase in corneal thickness after FS-LASIK(p=0.023,0.001);3.The change in thickness at corneal center after both SMILE and FS-LASIK showed significant correlation with pre-op SE(p<0.05).and The change in corneal thickness(△CT)in all regions,having no correlation with age,preoperative corneal thickness and postoperative spherical equivalent(SE)(P >0.05);4.5 years after SMILE,the thickness of cornea at the all regions of cornea were thickened 7.56μm、7.69μm、8.50μm、7.88μm、6.25μm、20.53μm than which at 6months,respectively.The changes were statistically significant(P≤0.030;5.The spherical equivalent,uncorrected visual acuity and best corrected visual acuity was-0.1016±0.2103D、Log MAR-0.123±0.115、Log MAR0.025±0.066 after SMILE 5years,and compared with6 months,there were no statistical differences(P > 0.05).Conclusions:1.In both SMILE and FS-LASIK groups,the corneal thickness in all three regions at week 1 were thinner than day 1.Both groups showed an increase in corneal thickness from 1 month to 3 months.The corneal thickness was comparable between3-and 6-month follow-up after SMILE whereas the central and the external annular region had a significant linear increase in corneal thickness after FS-LASIK.2.The variation of central thickness either SMILE or FS-LASIK were correlation with preoperative SE.The overall change of SMILE thickness is less than FS-LASIK,which indicates that the nomogram adjustment in the operation design.3.Compared with 6 months,the cornea in all regions were thickened after 5years of SMILE.There was no significant correlation between corneal thickness and the postoperative diopter.4.The equivalent spherical,uncorrected visual acuity and best corrected visual acuity were stable after 5 years of SMILE,and it had good stability. |
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