| Part Ⅰ General analysis and rare gas complications of femtosecond laser myopic(astigmatism)surgeryObjective:To explore the probability,type,cause of gas complications by analyzing the clinical and surgical data of 1032 eyes of FS-LASIK.To investigate the causes and treatment of rare gas retated complicationsMethods:Retrospective case series study.According to the records of intraoperative,operation videos and PDF images saved by femtosecond laser,the medical records of excimer laser operation center were consulted,and the data of eyes with gas related complications during operation were analyzed.1032eyes of LAS IK were divided into gas complication group and control group.The baseline and the clinical data of the two groups were compared.Vetical gas breakthrough and micro OBL were analyzed and reported.Results:Among1032 eyesof myopia,143 eyes underwent gas complications.The probability of occurrence was 13.86%(143/1032),including 114 cases of OBL(opaque bubble layer),96 cases(96 eyes)of single eye,18 cases(36 eyes)of double eyes,1 case(1 eye)of vertical gas breakthrough,9 cases(9eyes)of micro OBL,1 case(1 eye)of anterior chamber bubble.There were 889 eyes(782 double eyes and 107 single eyes)without gas complications.The canal offset value of the eyes with gas complications was 0.666 ±0.356mm,and that of the eyes without gas complications was 0.558±0.255mm,(t=3.164,P=0.002).The canal offset value of the eyes with vertical gas breakthrough was 0.1mm,and that of the contralateral eyeof the same patient without gas complications was 0.7mm.On the first day after operation,the thickness of 13 micro OBL eyes’ corneal flaps were 89.08±4.03μm measured by Optical coherence tomography,and it was 97.77 ± 4.94μm in the contralateral eyes of 13 patients(include other 4 micro OBL patients).All patients had been operated successfully.Conclusion:The incidence of complications in femtosecond laser assisted LASIK was 13.86%.A few patientsunderwentgasrelated complications such as OBL,micro OBL,vertical gas breakthrough and gas bubble in the anterior chamber.Compared with the contralateral normal eyes,the corneal flap of the eyes with micro OBL were thinner.The vertical gas breakthrough may be related to the short exhaust canal(small offset value of canal vent location)of cornea,and the appropriately increase of the length of exhaust canal can prevent the occurrence of vertical gas breakthrough.PartⅡ Cause analysis of opaque bubble layer in femtosecond laser in situ keratomileusisObjective:To analyze the cause and inducement of OBL in FS200 femtosecond laser in situ keratomileusis(FS-LASIK).Methods:Retrospective case control study.This study included 60 consecutive patients(120 eyes)with unilateral OBL during FS-LASIK.According to the occurrence of OBL,the eyes were divided into OBL eye group and non OBL eye(contralateral control eyes)group.The demography data,spherical equivalent diopter,corneal curvature,corneal astigmatism,central corneal thickness,intraocular pressure,and the vent location(length)of exhaust canal were collected.Through the determination of odds ratio(OR)and 95%confidence interval(CI),conditional Logistic regression analysis was carried out for the eyes in the two groups to find out the factors related to the occurrence of OBL.The canal offset values of 120 eyes were frequency analyzed.The incidence of OBL in the first and second half of 2017 was historical comparative analyzed.Results:There were no statistic differences between the two groups in terms of preoperative demographic data,spherical equivalent diopter,average K value,negative pressure 1st suction time,intraocular pressure and central corneal thickness.The OR value of the exhaust canal vent location was 5.5(95%CI was 2.31～13.13,P<0.01)in single factor Logistic regression.The OR value of corneal astigmatism diopter was 0.2(95%CI was 0.05～0.80,P=0.023)in single factor Logistic regression.The OR value of central cornea thickness was 1.18(95%CI was 0.95～1.45,P=0.13)in single factor Logistic regression.The P values of other parameters were all greater than 0.20.Multiple conditional Logistic regression analysis showed that the vent location(length)of exhaust canal(P<0.01,OR 7.16,95%CI 2.53～20.32)and corneal astigmatism(P=0.013,OR 0.13,95%CI 0.03～0.65)were significantly correlated with the incidence of OBL.The frequency analysis of canal offset value of 120 eyes also showed that the probability of OBL was the lowest when it was 0.4～0.6mm.A historical comparative analysis of the incidence of OBL in the first and second half of 2017 showed that the incidence of OBL decreased when the outlet of exhaust canal was located near the outside of corneoscleral limbus(x2=6.734,P=0.009).Conclusion:The incidence of OBL decreased significantly when the outlet of exhaust canal located at the outside of corneoscleral limbus.This may be due to more efficient exhaust canal.Corneal astigmatism is an independent protective factor for the complication of OBL.Part Ⅲ Effect of OBL on postoperative visual quality in femtosecond laser in situ keratomileusisObjective:To reveal the effect of OBL on visual quality after laser surgery by analyzing and comparing the data of preoperative examination and postoperative high-order aberrations,contrast sensitivity,visual acuity,diopter and astigmatism in OBL eyes and control eyes.Methods:Retrospective case control study.A retrospective case-control study was conducted between 132(78 hard)OBL eyes and 132 control eyes.The preoperative examination method and operation method refer to the first part.CDVA,BCVA,spherical and cylindrical diopter and astigmatism vector of OBL eyes and control eyes were followed up at 1,2,4,8 weeks and 6 months after operation.The total higher-order aberrations,spherical aberration,coma and trefoil were compared between OBL(hard OBL)eyes and non OBL eyes at 6 mm pupil.Less than 0.05 was the standard to judge the statistical difference of P value.Results:At the 1rd week after operation,the total higher-order aberrations were 1.56± 0.91μm in hard OBL group and 1.28 ± 0.72μm in non OBL group(t=2.433,P=0.016);At the 2nd week after operation,the total higher-order aberrations between hard OBL group and non OBL group were 1.53 ± 0.80μm and 1.29 ± 0.69μm(t=2.23,P=0.02 7).At the 1rd week after operation,the trefoil of the hard OBL group and non OBL group were 0.38±0.33μm and 0.29 ± 0.18μm(t=2.802,P=0.006);At the 2nd week after operation,the trefoil were 0.34 ± 0.31μm in hard OBL group and 0.26 ± 0.20μm in non OBL group(t=2.318,P=0.020);At the 4th week after operation,the trefoil were 0.30 ±0.19μm in hard OBL group and 0.24 ± 0.17μm in non OBL group(t=2.291,P=0.023);At the 8th week after operation,the trefoil was 0.28± 0.19μmin hard OBL group and 0.22 ±0.1 μm in non OBL group(t=2.168,P=0.031).Under the condition of dark vision and 3cpd frequency,the LogCS of hard OBL eyes were 1.56 ± 0.22 and the control eyes were 1.62± 0.19(t=2.281,P=0.024),1.65 ± 0.17 and 1.70 ± 0.17(t=2.071,P=0.040)in the second week,1.75± 0.21 and 1.81±0.16(t=2.047,P=0.042)in the four week.In other cases,there was no significant difference in LogCS between the two group eyes.There was no statistic difference in coma and spherical aberration between the hard OBL group and non OBL group.There was no statistic difference in UCVA,BCVA,spherical power,cylinder diopter,astigmatism vector,high order oberration,coma,trefoil and spherical aberration between the OBL group and non OBL group(P>0.05).Conclusion:The results of this study suggest that hard OBL may increase the total higher-order aberrations and trefoil in the early postoperative period.The LogCS value of hard OBL eyes decreased in the early stage under the 3 cpd frequency. |
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