Retro-orbital injection of FITC-dextran is an effective and economical method for observing mouse retinal vessels

PURPOSE To assess the effects of retro-orbital (RO) injection of fluorescein isothiocyanate dextran (FITC-dextran) for observing mouse retinal vessels. METHODS Oxygen-induced retinopathy (OIR) was induced in 7-day postnatal (P7) C57BL/6J mice by exposing them to a 75% oxygen atmosphere for 5 days and then returning them to room air at P12. At P17, 45 P17 OIR mice and 12 normal mice received an RO injection of FITC-dextran. Five P17 OIR mice were perfused with FITC-dextran via the left ventricle. Retinal flatmounts were viewed under a fluorescence microscope and a confocal microscope. Following RO injection or left ventricular (LV) perfusion, the areas of neovascularization, as well as the total retina areas, were measured and analyzed using Image Pro-Plus 5.1 software. RESULTS The suitable volume of FITC-dextran for RO injection to observe the retinal vessels of a P17 OIR mouse was 0.05 ml, the 5% volume required to achieve similar results by administering FITC-dextran using LV perfusion. The total retinal vessels in P17 OIR mice could be fully observed under a fluorescence microscope 3 s after RO injection of FITC-dextran. Our study showed that RO injection of FITC-dextran was suitable for observing the retinal vessels of all postnatal mice. There was no significant difference in evaluating retinal neovascularization between RO injection and LV perfusion of FITC-dextran (p>0.05). CONCLUSIONS Retro-orbital injection of FITC-dextran is an economical method for observing retinal vessels in mice, when compared with LV perfusion of FITC-dextran.