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S. Benac, A. Appel, M. Guthrie, J. J. Kang Derwent; Evaluation of Retinal Blood Flow and Vascular Structure in Early Stages of a Diabetic Animal Model. Invest. Ophthalmol. Vis. Sci. 2010;51(13):112.
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The goal of the study is to quantify changes in retinal blood flow and evaluate retinal structural changes in early stages of diabetes.
Measurements were acquired from anesthetized Long-Evans rats. Streptozotocin (55mg/ml/kg in 0.1 M citrate buffer, pH=4.5) was injected intravenously to induce diabetes (type I). Animal’s vitals, including blood glucose levels, were monitored weekly for up to 8 weeks. Scanning Laser Ophthalmoscope (SLO) infrared reflectance (IR) images were acquired to measure average diameter of arterial and venous vessels. SLO fluorescein angiography (FA) movies of 1µm yellow-green fluorescent microspheres (505nm maximum absorption and 515 nm maximum emission) were obtained to measure retinal blood velocity. The average diameter and average blood velocity were used to calculate average volumetric blood flow. FA images were used to evaluate any leakage or microaneurisms. Optical Coherence Tomography (OCT) was used to evaluate retinal thickness.
A significant weight loss and significant hyperglycemia were observed in the diabetic animals. A significant decrease (~25%) in arterial blood flow and a significant decrease (~11%) in venous blood flow were observed by 2 weeks post onset of diabetes. However, by week 3 the retinal blood flow values returned to the control values. No significant changes in the retinal structure were observed during this time frame. At week 2 when the retinal blood flow decrease was observed, the retinal thickness measurements remained similar to that of the control measurements (234 vs 238 µm).
By 2 weeks after the onset of diabetes, a significant decrease in blood flow values was observed, however, the vascular structure and retinal thickness were not affected. The results suggest that the alteration in the retinal hemodynamics in diabetic animals occur prior to any signs of structural change.
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