Fundus Changes Caused By Circulatory Disturbance Of Vortex Vein

BACKGROUNDVortex vein is the main ocular reflux vein and the only drainage system for the choroidal veins.The abnormalities of the vortex vein drainage system can lead to a variety of pathophysiological changes in the anterior segment,which could cause anterior segment ischemia and iris neovascularization.The pathogenic mechanisms of many fundus diseases,such as high myopia,diabetic retinopathy,central serous chorioretinopathy,age-related macular degeneration and polypoidal choroidal vasculopathy,are related to its abnormalities.Circulatory disorders in vortex vein system may cause structural and functional changes as well as hemodynamic changes in choroidal veins.OBJECTIVE:To establish animal model by ligating the vortex veins.To explore the acute and chronic changes of anterior segment and fundus caused by vortex vein ligation.To evaluate the acute and chronic hemodynamic changes in choroid.To assess the structural and functional changes in choroid vessels.METHODS:11 Cynomolgus monkey were randomly divided into 3 groups:group A,group B and group C.We randomly selected one eye as the experimental eye and the other eye as the control eye from each monkey in each groups.We ligated the superotemporal and inferotemporal vortex veins in group A and only the inferotemporal vortex vein in group B.We ligated the superotemporal and inferotemporal vortex veins combined with laser for the purpose of inducing choroidal neovascularization in group C.The monkeys were followed up for 12 weeks.Examinations including intraocular pressure measurement,slit lamp observation were performed on each eye on the day before operation,the operation day,the following 3 days after surgery and then once a week.FFA,ICGA and OCT were performed on each eye on the day before operation,1 day,1 week,4 weeks,8 weeks and 12 weeks after operation.The abnormalities of all the images were observed.The changes of ICG dye filling velocity and ICG dye outflow clearance time were analyzed.The choroidal vein diameters were analyzed in ICGA images by the use of Image J software.RESULTS:Vortex vein occlusion model was successfully established.Vortex vein ligation combined with laser induced CNV model was unsatisfactory.The intraocular pressures of the experimental group was significantly higher than those of the control group on the operation day,1 day and 2 day after operation(P<0.05).Some signs of anterior segment ischemia,including anterior chamber exudation,anterior chamber hemorrhage and iris congestion.FFA and ICGA images of one eye of experimental group in group A showed patchy fluorescence leakage in the superotemporal and inferotemporal quadrants in the first week after operation and tardy fluorescence filling or even no fluorescence filling in the same site in months after operation.Obvious delay in the filling of the temporal choroidal vascular bed was observed in the eyes of experimental groups in group A and C in the day after surgery(100%),which returned to normal in one week.Images of eyes of experimental groups in group A and C showed nonvisualization of choroidal veins in the ligation quadrants(incidence:87.5%in group A,50%in group C).The diameters of choroidal veins in the superotemporal quadrant of experimental groups of group A and group C were lower than those in control groups(P<0.05).There were no significant differences between the experimental groups and the control groups at other time points.The differences of ICG dye outflow clearance time were not statistically significant.The OCT examination results showed that the inferotemporal choroid thickness in the experimental group in group B was higher than that of control group within one week after operation.CONCLUSION:Vortex vein ligation animal model can be successfully established.Ligation of 1-2 vortex veins can cause choroidal circulation disorders in the short term,while some compensatory changes may happen in the choroidal circulation system in the long term.The animal model of vortex vein ligation may be more suitable for the study of acute choroidal circulation disorders.