| Purpose:To investigate the shapes and classifications of femtosecond laser-related intraoperative complications(OBL and black areas)during SMILE surgery,and possible risk factors of OBL and black areas,and further to evaluate the its effects on clinical outcomes(safety,efficacy,predictability,and stability)of SMILE surgery.Methods:Two retrospective nested case-control study were conducted in the study.Patients undergoing SMILE surgery for the correction of myopia and myopic astigmatism were enrolled in this study.Of this cohort,eyes developing OBL during surgery were included in OBL group,and eyes undergoing SMILE surgery at the same condition as OBL group and without any intraoperative and postoperative complications were included in control group.Likely,eyes developing black areas during surgery were included in black areas group,and eyes without any complications were included in control group.Two surgeons reviewed all surgical video at the same time to identify the occurrence and classification of OBL and black areas.The corneal keratometry,thickness,and dynamic deformation response parameters were used to analyze the possible risk factors for the occurrecnce of OBL and black areas.And we also evaluated the difference on BCVA,UCVA,and SE at the postoperative 1 day,1 week,1 month and 3 months between case groups and control groups.Multiple Logistic regression model was used to evaluate the risk factors of OBL and black areas.And correlation analysis was performed using Pearson or Spearman correlation analysis.Results:1.There were significantly statistical differences in SE,CCT,RST and LT between OBL group and control group(all P<0.001).There were significantly statistical differences in A1 Def A、HC Def A、HC Def Area、DAmax、Def Amax、SP between OBL group and control group(all P<0.05).There was an increased risk of OBL by 3% for every 1 μm increase in CCT(P<0.001).There was an increased risk of OBL by 3% for every 1 μm increase in RST(P=0.005).2.There were no significantly statistical differences in safety index between OBL group and control group at 1 day,1 week,1 month and 3 months after surgery,as well as in efficacy index(all P>0.10).At postoperative 3 months,2 eyes(10%)showed loss of two or more lines in BCVA in OBL group and 3 eyes(4%)showed loss of one or more lines in BCVA in control group.The proportion of UCVA>20/20 in OBL group and control group were 86%(18 eyes)and 87%(66 eyes),respectively.91% of eyes(19)was within ±0.50 D of the attempted spherical equivalent correction in OBL group and 80% of eyes(61)in control group.3.There was significantly statistical difference in femtosecond laser energy between black areas group and control group(P<0.001).The occurrence of the black areas was correlated with repeated suction(P=0.006).Subgroup analysis showed there were significant differences in Kf(P=0.038)and Ks(P=0.002)between the desertlike black areas and control group.There was an increased risk of black areas by 18% for every 5 n J decrease in femtosecond laser energy(P=0.005).4.There were significantly statistical differences in safety index between black areas group and control group at 1 day,1 week,1 month and 3 months after surgery(all P<0.05).The differences between black areas group and control group were statistically significant(P<0.05)except for the 3-month follow-up(P>0.05).At postoperative 3 months,3 eyes(14%)showed loss of two or more lines in BCVA in black areas group and 3 eyes(3%)showed loss of one or more lines in BCVA in control group.The proportion of UCVA>20/20 in black areas group and control group were 78%(18 eyes)and 91%(90 eyes),respectively.64% of eyes(18 eyes)was within ±0.50 D of the attempted spherical equivalent correction in black areas group and 89% of eyes(88 eyes)in control group.Conclusions:1.The thicker the cornea,the thinner the lenticule and the thicker the residual stromal bed thickness,the greater the risk on the occurrence of OBL in SMILE surgery.The harder the cornea,he greater the risk on the occurrence of OBL in SMILE surgery.2.The occurrence of OBL has little effect on visual acuity in SMILE surgery,but it has a certain influence on refractive diopter,resulting in postoperative residual SE and astigmatism,which may be related to the difficulty in surgical separation of lenticule.3.The black areas in SMILE surgery can be showed in a variety of shapes,related to the causes of the black areas.The occurrence of black areas in SMILE surgery is associated with repeated suction.When the femtosecond laser energy in the SMILE procedure is too low,the risk on the occurrence of black arease increases.4.The occurrence of black areas in SMILE surgery could affect the clinical outcomes and result in delay in postoperative visual recovery.Surgeons should pay attention to the black areas during surgery. |
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