| ObjectivesTo establish an experimental model similar to central retinal vein occlusion (CRVO) of human and observe the natural course of the disease. Methods1. Animal model building and fundus observation: An experimental model of retinal vein occlusion was been established photodynamically in cat left eyes. The fundus of the eyes were observed by fundus color photography and fundus fluorescein angiography (FFA) before and at day 1, 2, 3, 4, 5, 6, 7, 14 and 28 after occlusion.2. Retinal structure observation: 42 cats were divided into two groups by FFA: the group of recanalization within 3 days (group â… , n=16) and the group of recanalization after 3 days (group â…¡, n=26). Optical coherent tomography (OCT) was performed before and at day 3, 7, 14 and 28 after occlusion to observe the histological changes dynamically. At the end of the study, 3 cats selected randomly and respectively in the two groups were taken histopathologic examination and 3 cats were made digest preparation;Ink-perfusion retinal flat-mount was examined in the others, the right eyes as control.3. Retinal function examination: Flash electroretinogram (FERG) was recorded and statistically analyzed before and at day 1, 3, 7, 14 and 28 after occlusion.Results1. The model of RVO was established and observed in 42 cat eyes successfully. By day 28, all cats had recanalized their occluded veins. After occlusion, diffuse or cluster retinal hemorrhages, retinal edema and venous dilation were observed, together with delayed filling of the veins and dyeleakage from dilated capillaries. These changes developed at the first 3 days. In some animals, the lesions progressively improved but didn't return to normal values concomitantly with recanalization and collateral vessel formation, and in others large areas of retinal capillary nonperfusion were noted.2. OCT showed obvious absorption of retinal hemorrhages and edema at day 7 in group I but at day 14 in group II. Few capillary closures and a decrease in number of neuronal cells within the inner nuclear and ganglion cell layers were observed by light microscope in group I , but many capillary closures and an overall injury in group II.3. The amplitude of b-wave and OPs were significantly lower at day 28 after occlusion than those before occlusion, the latent time of a> b-wave delayed, and the change of the amplitude of a-wave had no difference. At day 28 after occlusion, the amplitude of b-wave and OPs were significantly lower in group II than those in group I , and the latent time of b-wave delayed, but the change of a-wave had no difference. In group I , the amplitude of b-wave started to recover after day 3, and increased obviously from day 7 to day 14. In group II, the amplitude of b-wave started to recover after day 7, and increased obviously after day 14. The amplitude of b-wave decreased in group II compared with group I at various times except day 1.ConclusionThe experimental model of several main retinal branch veins occlusion in cats can simulate CRVO of human. The time of retinal venous return recovering has influence on structure repairing and function recovering. Retinal function increased obviously with absorption of retinal hemorrhages and edema in the natural course of the model. The natural course of this model must not be mistaken for a beneficial effect of treatment. |
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