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Gilberto Raul Lopez Jaime, Amir H. Kashani, Saloomeh Saati, Gerald J. Chader, Mark S. Humayun; Variability of Vascular Oxygen Content in a Rabbit Retinal Vein Occlusion Model: A Study Using Hyperspectral Computer Tomographic Imaging Spectroscopy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2162.
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To study the variation in intravascular oxygen saturation during an acute retinal vein occlusion (RVO) in rabbits using snapshot hyperspectral computed tomographic spectroscopy.
Eleven rabbits (3-4kg) were dilated using 2.5% phenylephrine and 1% tropicamide ophthalmic drops and subsequently anesthetized with ketamine (50-80mg/kg) and xylazine (5-10mg/kg). Baseline retinal vascular oxygen measurements (oximetry) were made using a custom-made hyperspectral computed tomographic imaging spectrometer coupled to a fundus camera as previously described (Kashani AH et al. (2011)PLoS ONE 6(9): e24482). RVO were induced using multiple applications of argon green laser (Iridex Corp) to the vein following an intravenous injection of Rose Bengal (40 mg/kg); as described in (Ameri H et al.Graefes Arch. Clin. Exp. Ophthalmol. 2008; 246(10):1429-1439). RVO induction was confirmed after one hour by fluorescein angiography. Retinal oximetry measurements were repeated in selected arterial and venous branches one hour after RVO induction to evaluate changes in retinal vascular oxygen content. Comparison of oximetry before and after RVO was done with the Student T-test.
One hour after RVO induction, we observed statistically significant reductions in the intravascular oxygen saturation in temporal retinal arteries (85.1±6.5% vs. 80.5±6.9%, p<0.0001) and veins (72.4±4.5% vs. 64.2±4.3%, p<0.0001), respectively. There were no statistically significant differences in oxygen saturation measurements in the nasal control arteries and veins before and after temporal vein RVO induction, respectively (Arteries: 85.4±1.0% vs. 84.3±0.5%, p=0.37; Veins: 71.6±0.5% vs. 71.7±6.3%, p=0.87).
Using an animal model of acute RVO, we demonstrate acute changes in the intravascular oxygen content of arteries and veins within 1 hour of RVO induction. This study demonstrates that our snapshot hyperspectral computer tomographic spectroscopy system can detect significant variations in intravascular retinal oxygen saturation after an acute vein occlusion. Further investigation of retinal vascular disease models and human vein occlusions may provide useful and novel information in the evaluation and management of ischemic retinal diseases.
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