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S. Benac, K. Triandafilou, S. Tummala, A. Vankawala, J. J. Kang Derwent; Alteriations of Retinal Blood Velocity in the Early Stages of Diabetes in STZ Rats. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4973.
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The primary focus of the present study is to examine changes in retinal vessel diameter and blood velocity in early phase of diabetic state in streptozotocin (STZ) induced rats.
All measurements were obtained from anesthetized adult pigmented rats. Diabetes (type I) was induced by injecting STZ (50mg/ml/kg in 0.1 M citrate buffer, pH=4.5) via penile or tail vein. Blood glucose levels confirmed that hyperglycemia (>350 mg/100ml) was achieved. The animals were monitored weekly for six to eight weeks. Retinal blood velocity was determined by tracking 1 µm yellow-green fluorescent microspheres (505 nm maximum absorption and 515 nm maximum emission) in the vessels. Using the Scanning Laser Ophthalmoscope (SLO), retinal blood velocities were obtained in arteries, veins, and small vessels by recording several 2-min digital movies. Directional flow of fluorescent microspheres and vessel characterization were determined based on examination of infrared reflectance (IR) and fluorescein angiogram (FA) images.
A significant weight loss and excessive urinary excretion from diabetic animals were observed. After induction of diabetes, the arterial velocity showed an initial decrease of ~20%, followed by a small recovery by week 3. The venual velocity had a steady increase in early weeks reaching ~16% increase by week 3. Changes in diameters were not evident for initial weeks. Examination of IR and FA images showed no vascular changes in first 4 weeks following induction of diabetes, however, by week 6 there were noticeable vascular changes observed, mostly microaneurisms and leakage, based on FA images.
Blood velocity changed before blood vessel diameters or vascular changes associated with diabetes were observed. The results suggest that SLO-particle velocity measurement may be useful in detecting early changes in diabetes.
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