Objective To observe the safety and efficacy of posterior vitreous detachment (PVD) induced by combined intravetreal injection of lysineplasminogen and reteplase in rabbits.Methods Fifteen healthy New Zealand rabbits were divided into three groups with five rabbits in each. Take the right eyes as experimental eyes，while the left eyes as the control. The experimental eyes of three groups received combined intravetreal injection of 1250 mu;g/ml lysineplasminogen at 0.1 ml dose and 104U，3times;104U，105U reteplase at 0.05 ml dose recpectively, while the control eyes were injected intravetreally with 0.15 ml balanced salt solution. The conjunctiva, anterior chamber, lens, vitreous body, and retina were examined by slit lamp microscope and +120D preset lens. The retinal function was examined by electroretinogram (ERG).Results All the experimental eyes had PVD. The results of optical microscope showed that no change in retinal structure was found in the control group and 104 U reteplase group, clear retinal hierarchical but decreased ganglion cells and kernel layer cells were found in 3times;104 U reteplase group, only retinal pigment epithelium layer but no normal retinal structure was observed in 105U reteplase group. The results of ERG showed that compared the maximum mixed reaction of a and b wave amplitude in control group and reteplase group respectively, the difference was not statistically siginificant between 104U reteplase group and control group(a wave：t=0.881，-1.773，0.809；b-wave：t=-0.223，-0.441，1.400；P＞0.05),the differences were statistically siginificant between 3times;104 U(a wave：t=-3.20，b-wave：t=-4.182，-4.103),105 U reteplase group(a wave：t=-0.737，b wave：t=-15.150，6.597)and control group(P＜0.05). The control eyes didnprime;t had PVD.Conclusion Combined intravetreal injection of lysine-plasminogen and reteplase can induce complete PVD, and no damage to the retinal structure in rabbits.
Objective To observe the effect of medicineinduced posterior vitreous detachment (PVD) on proliferative vitreoretinopathy (PVR). Methods PVR was induced in the left eyes of 24 pigmented rabbits by intravitreal injection with platelet rich plasma. The rabbits were randomly divided into two experimental groups (group A and B) and one control group with 8 eyes in each group. Three hours later, the eyes in group A and B and the control group underwent intravireal injection with 1 U plasmin 0.05 ml+20 U hyaluronidase 0.05 ml, plasmin 0.1 ml, and balance salt solution 0.1 ml, respectively. The grade of PVR was recorded 1, 7, and 28 days after the intravitreal injection, and the eyes were examined by flash electroretinogram (FERG), B-scan, and retinal histopathological examination. Results The PVR models of rabbit eyes were induced successfully. On the 7th day after injection, complete and partial PVD was found in 5 and 3 eyes respectively in group A; partial PVD in 5 eyes and no complete PVD was observed in group B; there was no PVD in the other 3 eyes in group B and also in the eyes in the control group. On the 28th day after intravitreal injection, PVR grade of group A and B were both obviously lower than that of the control group（D=75.6, 98.9；P=0.003，P=0.011）; On the 7th and 28th day after injection, the b-wave amplitude in group A and B was significantly higher than that in the control group; PVR grade of the PVD eyes was lower than that of nonPVD eyes; PVR grade of the complete PVD eyes was only 0～1. Conclusions Three hours after the PVR models of rabbit eyes were induced, complete PVD induced by intravitreal injection of plasmin combined with hyaluronidase could prevent the development of PVR of rabbit eyes in some degree; partial PVD induced by plasmin alone or combined with hyaluronidase could relieve the development of PVR.
Objective To detect the effects of plasmin combined with hyaluronidase or hexafluoride SF6 on inducing posterior vitreous detachment (PVD). Methods Eighteen young pigmented rabbits were randomly divided into group A, B, and C with 6 rabbits in each. All of the right eyes were the experimental eyes and the left ones was the control. The right eyes in group A, B, and C were injected with plasmin 1 U, plasmin 1 U and hyaluronidase 20 U, and plasmin 1 U and SF6 0.5 ml, respectively; while all of the left eyes underwent intra-vitreous injection with balanced salt solution 0.1 ml. The eyes were observed by indirect ophthalmoscopy, slit lamp examination, biomicroscopy, B-ultrasonography, and electroretinography (ERG) before and after injection respectively. At last, the retinal sections were examined by light microscopy, scanning and transmission electron microscopy. Results The results of scanning microscopy showed incomplete PVD in 2 (33.3%) experimental eyes in group A, and complete PVD in 4 (66.7%) experimental eyes in both group B and C, and the positive rate of PVD in both group B and C significantly differed from that in group A (Plt;0.05). The b-wave amplitudes of ERG in the three groups after injection didn’t differ much from that in the control group or before the injection（Pgt;0.05）. The results of transmission electron microscopy and light microscopy indicated unchanged retinal structure. Conclusions Compared with the application of only plasmin, plasmin combined with hyaluronidase or hexafluoride SF6 can induce complete PVD more efficiently and do no harm to the retina. (Chin J Ocul Fundus Dis, 2005, 21: 388-390)
Objective To investigate the effects of intravitreal injection of matrix metalloproteinase-3 (MMP-3) on the vitreoretinal adhesion and the vitreous gelatin. Methods Twenty-four pigmented rabbits were randomly divided into 3 experimental groups（group A, B, and C）and one control group with 6 rabbits (12 eyes) in each. Different concentrations of 0.1 ml MMP-3 (5,10, 20 ng in group A, B, and C, respectively) and equivalent dose of balanced salt solution were intravitreally injected to the rabbits, respectively. Clinical examinations (such as gross observation, slit-lamp biomicroscopy, indirect fundus ophthalmoscopy ), electroretinography (ERG) and fundus fluorecein angiography (FFA) were taken before and after injection. Results One week after injection, posterior vitreous detachment (PVD) and focal vitreous liquefaction were recognized clinically for the first time in 1 eye in group B. By the end of this study, clinically detected PVD developed in 1 eye in group A, 3 eyes in group B, but the synchisis developed slowly, and no liquefaction or PVD occurred in control group. As for the histological examination, partial PVD was observed in 1 eye in group A and 3 eyes in group B 60 minutes after injection. All of the eyes in group A and B showed partial PVD 1 week after injection, and the area of PVD enlarged in contrast with before. Complete PVD were recognized in 1 eye in group A and 3 eyes in group B 15 weeks after injection, and the cleavage was narrow and limited. In group C, inflammatory cell infiltration in the inner layer of retina, destruction of retinal structure, and fluorescein leakage at late phase was found in the early period after injection. Conclusions MMP-3 is effective in disrupting the adhesion of the posterior hyaloid to the inner limiting membrane leading to PVD, and helpful to some extent in producing vitreous liquefaction. The dose of 10 ng MMP-3 is safe and effective for the rabbits eyes, which may be used as an promising assistant of vitreous surgery. (Chin J Ocul Fundus Dis，2004，20：67-132)
Objective To investigate the dosage, efficacy and safety of intrav itreal injection of plasmin in producing posterior vitreous detachment (PVD), an d the possible role of plasmin in degrading adhesion glycoproteins of inner limiting membrane (ILM).Methods Twenty eyes of young human cadavers within 24 hours after death were divided into 4 groups that received 0.1 ml balanced salt solution (group 1) as control, 1 (group 2), 2 (group 3), or 3 (group 4) U of human plasmin. Optical and transmission electron microcopies were performed to examine the ultrastructure of the vitreoretinal interface. Electron-immunocytochemical techniques were carried out on ILM to estimate the content of fibronectin (FN) and laminin (LN). Flow cytometry was used for cell viability analysis of variance (ANOVA) and Tukey-test was employed for statistical analysis. Results Microscopy demonstrated that plasmin especially in group 4 cleaved the attachment of the vitreous collagen fibrils to the ILM with no evident damage to the inner retina. The content of LN, FN in ILM decreased with injection of plasmin (group 3 and 4 had statistical significance from control group for FN,P＜0.05; for LN in group 4, P＜0.05). Retinal cell viability was similar for plasmin-treated and control eyes. Conclusion Human plasmin disrupts the attachment of posterior hyaloid to the ILM with no morphologic changes of the inner retina. PVD is induced mostly with injection of 3 U plasmin. (Chin J Ocul Fundus Dis，2003，19：42-45)