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A. A. Jangi, G. Landa, R. Rosen, J. Walsh, P. Garcia; Retinal Blood Flow Velocity in Normal Subjects Using the Retinal Function Imager. Invest. Ophthalmol. Vis. Sci. 2008;49(13):901.
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To determine retinal venous blood flow velocity and arterial blood flow velocity in normal subjects using the Retinal Function Imager.
The Retinal Function Imager (RFI) (Optical Imaging, Rehovot, Israel) provides direct visualization and measurement of retinal blood flow velocity. The RFI system is composed of a standard fundus camera to which a customized stroboscopic flash lamp system and a fast digital camera have been added. The blood flow velocity measurement is achieved by the fact that hemoglobin-filled erythrocytes in the bloodstream provide a natural, high contrast chromophore which directly marks the flow of blood. Tracking of these erythrocytes gives a direct measure of their velocity. Eight consecutive flashes with an inter-flash interval of less than 20 msec are delivered to a patient. Sequences of eight frames each are obtained from each patient in the way of standard fundus cameras.Automated flow velocity quantification is achieved by using a path-constrained cross-correlation technique. Path templates (essentially tracings over the blood vessels to be analyzed) are generated by an experienced operator via a method combining user supervision with automatic detection. The instrument's analysis software provided quantitative analysis of the retinal blood flow characteristics.We looked at the average blood flow velocities in retinal veins and arteries.
We conducted a study of 22 eyes with an average age of 48.8 years. The average venous blood flow velocity was 5.1mm/sec in the right eye and 4.3 mm/sec in the left eye. The average arterial blood flow velocity was 5.9mm/sec in the right eye and 5.3mm/sec in the left eye. Although in our sample, both venous and arterial blood flow velocities were found to be faster in the right eye when compared to the left eye, these results were not statistically significant (p-value 0.22 and 0.42 respectively). We also compared average venous and arterial blood flow velocities in males and females. We studied 8 male eyes and 14 female eyes. The average venous blood flow velocity was 4.6mm/sec in males and 4.8mm/sec in females (not statistically significant p-value = 0.72). The average arterial blood flow velocity was 5.5mm/sec in males and 5.6mm/sec in females (not statistically significant p-value = 0.90).
Further studies and a larger patient population are needed in order to determine significant relationships between identifiable variables and venous and arterial retinal blood flow velocity values.
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