Abstract
Purpose:
The purpose of this study was to evaluate a method of mapping volumetric blood flow from dynamic fluorescein enhanced fluorescent imaging in normal and diabetic rat retinas.
Methods:
Long-Evans rats were randomly separated into two groups: a control group and a diabetic group. Diabetes was induced by streptozotocin (STZ, 80 mg/kg) injection into the tail vein. By 4 weeks post-STZ injection, the average blood glucose in the diabetic rats was 406 ± 121 mg/dL. Under ketamine (80 mg/kg BW) and xylazine (10 mg/kg BW) anesthesia, a bolus of fluorescein dye (0.1 mL of 10%) was injected via tail vein to obtain videoangiograms (30 sec, 20 fps, 256x256) using a Heidelberg scanning laser ophthalmoscope. The fluorescein images were loaded into MATLAB and “plug flow” tracer kinetic model was applied to obtain retinal blood flow maps.
Results:
The blood flow maps for control rat retinas exhibited the highest volumetric blood flow in the large arteries and veins, with substantially lower tissue flows. In contrast, the blood flow maps in the diabetic rat retinas showed a high tissue flow. The tissue blood flow was significantly higher (P<0.01) in the diabetic rats compared to the controls: 7.6±1.7 ml/min/100g in the control rats and 25.6±13.9 ml/min/100g in the diabetic rats. Tissue blood volumes were also significantly larger (P<0.05) in the diabetic rats compared to controls: 0.13± 0.08 ml/100g in the control rats and 0.29±0.14 ml/100g in the diabetic rats.
Conclusions:
The current data showed an increase in blood flow in diabetic animals similar to previous studies suggesting that the dynamic fluorescein enhanced fluorescent imaging method can detect changes in blood flow based on fluorescein angiogram. The proposed technique is a novel technique to study retinal blood flow and can be readily translated clinically to examine early changes of blood flow in diseases such as diabetic retinopathy.