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Ray Zhang, Qianhaozhe You, Gabriel Martin, Mark S Humayun, Amir H Kashani; Retinal Vascular Oxygen Saturation in Diabetic Rats: A Study using Hyperspectral Computed Tomographic Imaging Spectroscopy. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4427.
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© ARVO (1962-2015); The Authors (2016-present)
To assess changes in retinal vascular oxygen concentration in a diabetic rat model using hyperspectral computed tomographic imaging spectroscopy (HCTIS).
Nine brown Norway rats were anesthetized and dilated for retinal imaging. Six rats were injected with 65mg/kg of Streptozotocin (STZ) to induce hyperglycemia, and 3 rats with 0.9% saline control. Blood glucose levels were measured after a 12 hour fast using Accu-Chek Aviva Plus glucometer (Roche Inc). Baseline oximetry measurements and fundus photographs were taken in both eyes of each rat. HCTIS oximetry measurements were taken every 2 weeks after STZ injection for up to 2 months. The same vessel areas were selected for analysis at each time point. Fundus photos and FA were repeated at 2 months. Comparison of retinal arterial (Aox) and venous (Vox) oxygen saturation levels were made at each time point using the Student T-test.
All experimental rats developed and maintained hyperglycemia (mean 410±41 mg/dl), and all control rats remained normoglycemic (mean 124±24 mg/dl) over the 2 months of the study. For control rats (n=3) mean Aox was 95±1%, 100±4%, 97±6%, 102±5%, and 100±7% and mean Vox was 90±4%, 88±3%, 86±3%, 87±2%, and 87±5% at baseline, 2, 4, 6, and 8 weeks. For experimental rats (n=6) mean Aox was 91±2%, 94±4%, 91±4%, 94±3%, 94±5% and mean Vox was 89±3%, 90±4%, 88±2%, 86±3%, 85±3% at baseline, 2, 4, 6, and 8 weeks. There were no significant differences between control and experimental Aox and Vox for each time point. The arteriovenous difference at each time point also showed no clear trends. Vox measurements in the diabetic rats showed a decreasing Vox trend over time when compared with baseline (p=0.76, 0.57, 0.17, 0.07).
There was a trend towards decreasing Vox over 2 months time in experimentally induced diabetic rats but this was not statistically significant. There were no significant differences in Aox and Vox in rats with experimentally induced diabetes versus controls. HCTIS is a useful method for measuring retinal vascular oxygen content in the rat model.
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