Evaluation of the vascular leakage and retina thickness using OCT combined with FFA in STZ-induced diabetic rat model

Background Streptozocin (STZ)-induced SD diabetic rat model is often used in the study of diabetic retinopathy (DR).The research approach of retinas in DR model previously is in vitro study.Fluorescein fundus angiography(FFA) and optical coherence tomography (OCT) are available for the in vivo observation of ocular fundus.But the combination of FFA and OCT used to dynamic evaluation of DR is less well-known.Objective The purpose of this study was to investigate the changes of retinal vessel and capillary as well as retinal thickness in STZ-induced diabetic SD rat.Methods Sixty clean SD rats were randomized into two groups according to random number table.STZ dissolving in sodium citrate solution was intraperitoneally injected to establish diabetic animal models in the diabetic group,and equivalent amount of sodium citrate solution was used in the same way in the control group.FFA and Spectralis HRA+OCT(SD-OCT) were used to dynamically identify the fluorescine leakage of retinal vessels and thickness of retinas in the superior,inferior,nasal and temporal retinas in the left eyes 4,8,12 weeks after injection.The use and care of experimental animals complied with the relative statement of National Institutes of Health (NIH,USA).Results FFA exhibited that the optical disc located at the center of retina,and retinal vessels run in radical pattern.The choroidal fluorescence disappeared 60 seconds after intravenous injection of fluorescine sodium.So repeatedly injection was needed for multiple parts of imagine.No fluorescine leakage was found in rat retinas from initial until 12 weeks after modeling.OCT examination showed a similar imaging in SD rat to human,with 10 layers of tissues,which was consistent with those in histopathological image.No significant differences were found in retinal thickness as well as inner and outer limiting membrane thickness among the superior,inferior,nasal and temporal retina from 2 disc diameter (DD) away optical disc (P＞0.05).Compared with normal SD rats,retinal thickness and inner and outer limiting membrane thickness were no significant difference 4,8 weeks after modeling (all at P＞0.05),and retina and inner and outer limiting membrane in 12 weeks were thicker than those in normal rats (all at P ＜ 0.05).The analysis outcome from OCT was not totally consistent with that from histopathological examination.Conclusions Combination application of SD-OCT and FFA is helpful for the in vivo assessment of early DR of rat. Key words: Tomography optical coherence;  Diabetes mellitus, Experimental/complications;  Diabetic retinopathy/pathology;  Capillary permeability;  Fluorescein angiography;  Disease model, animal