Comparison Of Functional Optical Zone After SMILE And Femto-LASIK For High Myopia

Purpose: To compare the functional optical zone(FOZ)and analyze the related factors after small incision lenticule extraction(SMILE)and femtosecond laser–assisted laser in situ keratomileusis(Femto-LASIK)for correction of high myopia.Methods: This retrospective case-control study included 69 patients(69 eyes)in SMILE group and 69 patients(69 eyes)in Femto-LASIK group after correction of high myopia in JSIEC from December 2016 to December 2019.All of the right eyes were analyzed in the study.Visual acuity(including UCVA and BCVA),refractive errors were measured and corneal tangential curvature and total corneal high order aberrations(HOAs)were measured by Pentacam corneal topography preoperatively and 3 months postoperatively in both groups.FOZ was measured by Image J software on tangential curvature difference map before and 3 months after surgery from Pentacam.The tangential curvature difference map was imported into Image J software to measure the FOZ diameter and decentration of the FOZ in the two groups.Results: The mean preoperative spherical equivalent(SE)was-6.88 ± 0.79 D in SMILE and-7.03 ± 0.80 D in Femto-LASIK(P = 0.297).The mean planned optical zone(POZ)was 6.48± 0.15 mm in SMILE and 6.45 ± 0.18 mm in Femto-LASIK(P = 0.224).At 3 months postoperatively,the SE in SMILE and Femto-LASIK was-0.04 ± 0.22 D and-0.01 ± 0.35 D(P = 0.548).The mean FOZ were 4.80 ± 0.41 mm in SMILE and 4.41 ± 0.33 mm in FemtoLASIK.Postoperative decrease in FOZ was 1.69 ± 0.42 mm in SMILE significantly lower than2.04 ± 0.34 mm in Femto-LASIK(P < 0.001).Postoperative increase in RMS of the corneal wavefront aberrations,including HOAs,spherical aberration(SA),coma and trefoil were less in SMILE than in Femto-LASIK.The RMS of HOAs and SA were increased significantly in FemtoLASIK group compared with SMILE group(P = 0.002 and P < 0.001).The size of the FOZ in the SMILE group was significantly positively correlated with POZ(P < 0.001),and negatively correlated with the increase of the RMS of HOAs,SA and coma(P < 0.001).The size of the FOZ in the Femto-LASIK group was significantly positively correlated with the POZ(P = 0.001),was negatively correlated with the increase of RMS of HOAs,SA and coma(P = 0.016,P < 0.001,P= 0.035).Conclusions: SMILE resulted in less FOZ reduction than Femto-LASIK during correction of high myopia.The RMS of HOAs and SA increased significantly in the Femto-LASIK group compared with the SMILE group.In order to obtain larger FOZ,patients can give priority to SMILE for high myopia correction.