| PURPOSE:In this part,we observed the histopathological changes of rabbit lens in the early period after the pars plana vitrectomy with nonexpansile perfluoropropane gas,gauged LECs apoptosis and analysed relationship between them and perfluoropropane gas and complicated cataract.METHODS:37 new zealand healthy rabbits(74 eyes)were assigned randomly to three groups:normal group,control group and experimental group.The A group-7 rabbits(14 eyes)was normal group; the B group-30 eyes were control group,performed the operation of simple vitrectomy with BSS;the C group-30 eyes were experimental group,performed the operation of vitrectomy with nonexpansile perfluoropropane gas.The intraocular pressures were measured with Schiotz indentation tonometer,and the lens shape were observed with slit lamp microscope on the 1st,3th,8th,35th,45th day after operation.The optical microscope and electron microscope specimens were made with rabbit lens on the 1st,3th,8th,35th,45th day after operation.The microstructure changes of LECs,equatorial region and cortex below posterior capsule of rabbit lens were observed with optical microscope and the ultrastructural changes of LEC were observed with transmission electron microscope.On the 45th day after operation,LEC smears were made with rabbit lens of exprerimental group for gauging AI(TUNEL method)and Caspase-3 positive rate(immunohistochemistry SABC method),meanwhile analysed the relativity between them.RESULTS:1.IOP:There was no significant difference(P＞0.05)of IOP among the three groups on the 1st,3th,8th,35th,45th day after operation.2.The lens opacity degree:There was no distinct opacity on the rabbit lens of normal group and control group on the 1st,3th,8th,35th,45th day after operation.The opacity rate of experimental group was 93.33%.There was significant difference(p＜0.0125)between experimental group and the control group,normal group on the 1st,3th and 8th day after operation.The occurrence rate and degree of cataract was positively correlated with the area and time of contact between perfluoropropane gas and lens,but the opacity alleviated or dead away gradually with the disappearance of perfiuoropropane gas.3.The lens histopathological changes:optical microscope:There was no evident abnormal of lens microstructure of the control group and normal group on the 1st,3th,8th,35th,45th day after operation.The LECs of experimental group were found only cellular edema on the 1st,3th,8th day after operation,and denature,and some irreversible changes such as necrosis,cell overlaps and so forth on the 35th,45th day after operation.transmission electron microscope:There was no evident abnormal of lens microstructure of the control group and normal group on the 1st,3th,8th,35th,45th day after operation.The LECs of experimental group were found only cellular edema on the 1st,3th,8th day after operation,Chromosome circling and set on the 35th day after operation,and characteristic apoptotic bodies on the 45th day.4.The AI of LECs:Mean AI(normal group)is 0.19%,that of control group and experimental group is respectively 0.21%and 15.10%.There was no significant difference(P＞0.0125)of AI between the normal group and the control group,There was significant difference(p＜0.0125)of AI between experimental group and the control group,normal group on the 45th day after operation.5.Caspase-3 positive rate:Mean Caspase-3 positive rate(normal group)is 0.61%,that of control group and experimental group is respectively 1.11%and 45.23%.There was no significant difference(P＞0.0125)of Caspase-3 positive rate between the normal group and the control group,There was significant difference(p＜0.0125)of Caspase-3 positive rate between experimental group and the control group,normal group on the 45th day after operation.6.The Caspase-3 positive ratio was positively correlated with AI of LECs(r_s=0.69,p＜0.05)on the 45th day after operation in experimental group.CONCLUSIONS:1.The perfluoropropane gas could cause the transient cataract in the early period after this operation.The occurrence rate and degree of cataract was positively correlated with the area and time of contact between perfluoropropane gas and lens.2.Although cataract is transient caused by the perfluoropropane gas in the early period after this operation,it occurs irreversible changes.3.pars plana vitrectomy with the perfluoropropane gas tamponade could lead to lens epithelial cells apoptosis.4.LECs apoptosis in the early period after pars plana vitrectomy with the perfluoropropane gas tamponade on rabbit eyes correlate with Caspase-3 express elevation.5.Histopathological changes including transient and permanent damage,and apoptosis of rabbit lens in the early period after the pars plana vitrectomy with nonexpansile perfluoropropane gas,maybe one of main cause of complicated cataract.
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