Retro-orbital injection of FITC-dextran combined with isolectin B4 in assessing the retinal neovascularization defect

BACKGROUND: A reliable and effective method is required to deliver agent that can aid the in vivo imaging of retinal vessels. The aim of the present study was to evaluate retro-orbital (RO) injection of fluorescein-labeled isothiocyanate dextran (FITC-dextran) as a method of demonstrating retinal neovascularization (NV) and avascular areas in oxygen-induced retinopathy (OIR) mice. METHODS: Different concentrations of FITC-dextran were used to compare the efficacy of this agent in perfusing the retinal vessels. Hematoxylin–eosin (HE) staining was used to evaluate the safety of RO injection. The vitreous blood vessels and extent of NV were assessed in P17 OIR mice using FITC-dextran and compared with the corresponding measurements obtained following isolectin B4 staining or the combination of both methods. RESULTS: The fluorescence of small vessels and neovascular tufts could be observed clearly following RO injection of 0.05 ml of 25 mg/ml or 50 mg/ml FITC-dextran. No visible damage to tissues adjacent to the injection site was discovered. Vitreous blood flow was gradually reduced from P0 to P5 and eventually disappeared in P17 OIR mice, as demonstrated by FITC-dextran perfusion. The retinal NV areas assessed by isolectin B4 were larger than those assessed by FITC-dextran, but the retinal avascular areas were smaller. The combination of both methods could conduce to distinguish non-functional blood vessels. CONCLUSIONS: RO injection of FITC-dextran combined with isolectin B4 is an effective, optimal method for assessing the NV area and avascular area.