| Objective:To compare the visual acuity,diopter and changes of corneal posterior surface elevation after small incision lenticule extraction(SMILE)and femtosecond laser lenticule extraction(FLEx)for high myopia and analyze related factors that may affect the changes of corneal posterior surface elevation.Methods:A total of 47 patients(90 eyes)with high myopia who underwent refractive lens extraction at the Laser Refractive Correction Center of the Second Hospital of Jilin University from January 2016 to January 2017 were included.The FLEx group includes 25 patients(47 eyes)and the SMILE group includes 22 patients(43 eyes).All patients underwent routine preoperative examinations,including uncorrected distance visual acuity(UDVA),manifest optometry and mydriatic optometry,non-contact intraocular pressure(IOP),corneal topography,comprehensive optometry,corrected distance visual acuity(CDVA),central corneal thickness(CCT),anterior segment and fundus examination after mydriasis under the slit lamp.All patients were reexamined 1 day,1 week,1 month and 1 year after surgery,and UDVA and manifest optometry were recorded.The UDVA and diopter of the two groups were compared at each time point.The corneal topography was performed at the first year after surgery.The changes of corneal posterior surface elevation were obtained on the comparison map(A-B map)(the preoperative corneal posterior surface elevation-the postoperative corneal posterior surface elevation).The mean changes of corneal posterior surface elevation were examined respectively at the corneal vertex,2mm ring,4mm ring,and 6mm ring.The mean change of corneal posterior surface elevation at the 2mm ring is the average of elevation changes at 4 points including 0°,90°,180° and 270° on the 2mm ring;the mean change at the 4mm ring is the average of elevation changes at 8 points on the 4mm ring including 0°?45°?90°?135°?180°?225°?270° and 315°;the mean change at the 6mm ring is the average of elevation changes at 12 points on the 6mm ring including 0°?30°?60°?90°?120°?150°?180°?210°?240°?270°?300° and 330°.The changes of corneal posterior surface elevation were compared between the two groups at the first year after surgery,and related factors that may affect the changes of corneal posterior surface elevation were analyzed.Data were analyzed statistically using independent t test,paired t test,chi-square test,and Pearson correlation analysis.Results:1.The mean UDVA(LogMAR)at 1 day,1 week,1 month,and 1 year after surgery were 0.01±0.09,-0.06±0.07,-0.06±0.07,and-0.06±0.09 in the FLEx group,respectively,and 0.02±0.09,-0.06 ± 0.07,-0.05 ± 0.07 and-0.05 ± 0.08 in the SMILE group.The mean UDVA of both groups were better at 1 week than 1 day after surgery,but there was no significant difference between 1 month and 1 week after surgery,and 1 year and 1 month after surgery.And there was no significant difference in UDVA between the two groups at each time point.2.The proportion of spherical equivalent(SE)in the range of ±0.5D after 1 day,1 week,1 month and 1 year after operation were 66.0%,70.2%,66.0% and 72.3% in the FLEx group,respectively,and 74.4%,74.4%,69.8%,and 69.8% in the SMILE group.And the proportion of surgical eyes within ±1.0D were 89.4%,93.6%,100%,and 95.7% in the FLEx group,respectively,and 97.7%,90.7%,93.0%,and 93.0% in the SMILE group.There was no significant difference between the two groups in the proportion of surgical eyes within ±0.5D and ±1.0D at each time point.3.The mean changes of posterior surface elevation 1 year after surgery at the corneal apex,2mm ring,4mm ring,and 6mm ring were 1.58 ± 1.70,0.97 ± 0.64,-0.88 ± 0.61 and-1.63 ± 1.61 in the FLEx group,respectively,and 1.21±1.60,0.91±0.78,-0.38±0.67,and-0.89±1.64 in the SMILE group.There was no significant difference between the two groups in the mean changes of posterior surface elevation at the corneal apex and 2mm ring,but the changes in the FLEx group were significantly higher than the SMILE group at the 4mm ring and 6mm ring.4.Postoperative changes of posterior surface elevation in different regions of two groups had no significant correlation with preoperative IOP,SE,CCT,the ratio of intraoperative cutting thickness(intraoperative cutting corneal thickness/preoperative CCT),and the ratio of residual bed thickness(the residual bed thickness/preoperative CCT).Conclusions:1.The mean UDVA were better at 1 week than 1 day after surgery in the FLEx group and SMILE group,then UDVA remained stable.2.There was no significant difference in UDVA and diopter between the FLEx group and SMILE group at each time point after surgery,and both groups had good predictability,efficacy,safety,and stability.3.After FLEx and SMILE,the central area(apex and 2mm ring)of the corneal posterior surface moved backward,while the peripheral area(4mm and 6mm ring)moved forward.4.The displacement of peripheral area of the corneal posterior surface(4mm and 6mm ring)were significantly higher in the FLEx group than that of the SMILE group,while there was no significant difference between the two groups in the central area(apex and 2mm ring).5.There was no significant correlation between the postoperative changes of posterior surface elevation in different regions and preoperative IOP,SE,CCT,the ratio of intraoperative cutting thickness and the ratio of residual bed thickness in both groups. |
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