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S. Benac, S. Tummala, H. Tran, J. J. Kang Derwent; Quantification of Retinal Blood Flow in Response to Alterations of VEGF Level. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2087. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The main objective of this study was to investigate the effect of Vascular Endothelial Growth Factor (VEGF) levels on retinal blood flow and vasculature.
All measurements were performed on anesthetized adult pigmented rats. Retinal blood velocities of arteries, veins, and small vessels (blood vessels <40µm diameter) were determined by tracking 1µm yellow-green fluorescent microspheres (505 nm maximum absorption and 515 nm maximum emission) using a Scanning Laser Ophthalmoscope (SLO). Changes in vessel diameter were determined based on SLO infrared reflectance (IR) images. The retinal blood flow of each vessel type was calculated based on cross sectional area and average velocity of the vessel. Fluoroscein angiography (FA) images were used to examine structural alterations of the vessels. Two different concentrations of VEGF, 29.7ng/µl (367nmol/L vit conc) and 50ng/µl (619nmol/L vit conc), were administered intravitreally. IR and FA images and particle tracking movies were obtained at 48 hours and 1 week post-injection.
At 48 hour post-injection time period, significant vasodilation and tortuosity were observed in the retinal vessels in response to a high dose VEGF injection while the lower dose of VEGF injection had a minimal effect on the structural changes. In response to a lower dose of VEGF (367nmol/L vit conc), hemodynamic changes were not observed throughout the 48 hour and 1 week time period. At a high dose of VEGF (619nmol/L vit conc) blood velocities and blood flow rates showed an increase by 48 hours post-injection. In particular, the arterial blood flow rates increased ~20% and venous blood flow rates showed ~40% increase. The small vessels showed ~27% increase in blood velocity.
By utilizing the SLO particle tracking method, changes in blood flow rate due to alteration of VEGF level in the eye were quantified. The vascular structural changes were dose-dependent where larger alterations in vasculature and retinal blood flow rates were produced at a higher VEGF concentration.
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