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D. Nelson, R. Ben–Cnaan, M. Rosner, M. Belkin, A. Grinvald; Reduction of the Variance of Blood–Flow Velocity Measurements by Triggering on the Heartbeat–Cycle Phase . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2650.
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© ARVO (1962-2015); The Authors (2016-present)
Fundus imaging is essential for diagnosing and monitoring common ophthalmic and systemic diseases. The Retinal Function Imager (RFI) is a non–invasive, easy to use, direct qualitative and quantitative imaging method that extends the utility of fundus imaging by providing quantitative information about retinal blood flow velocity. It can also be used for blood oximetry, capillary bed topography, and examining the metabolic state of the retina. Here we concentrated on characterizing blood flow velocity in retinal arteries and veins and accomplishing a nearly two–fold reduction of the variance of blood–flow velocity measurements by coupling the measurement to the heartbeat–cycle.
One eye of each of 14 healthy volunteers (mean age 30.7 years) was tested. Each subject had at least two separate sessions of imaging using the RFI.
The mean velocity in non–heartbeat synchronized subjects was 6.1± 2.4 mm/sec for secondary and tertiary macular artery segments, and 4.4 ± 2.1 mm/sec for secondary and tertiary macular vein segments. The velocities of such vessels as appeared in all trials for a particular subject eye were averaged within each trial to produce a (macular) "global velocity" measurement, that allowed inter–trial velocity variability to be measured. The average global velocity was 5.0 mm/sec; the average standard deviation, 17% of subject eyes' mean global velocity. After adjusting for the heartbeat cycle phase, global velocity variability among trials decreased to 10%.
The RFI provides a non–invasive, simple, rapid and reliable technique for direct retinal blood flow velocity measurement of low variance. This may become an important tool for diagnosis and follow–up in ophthalmology.
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