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R.P. Tornow, O. Kopp, B. Schultheiss; Time Course of Fundus Reflection Changes According to the Cardiac Cycle . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1296.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the time course of fundus reflection at different retinal locations with cardiac parameters. Methods: Video sequences (25 frames/sec) of the ocular fundus (acquired using a Zeiss fundus camera FF450, 30 deg field, green filter, CCD camera) were digitized online on hard disk. For quantitative imaging, a linear transfer function was used and the offset of the entire image aquisition system (CCD camera / imaging board) was measured and compensated. All images of an acquired sequence were aligned offline to compensate for eye movements. The time course of reflection R(t) and the pulsatile reflection component ΔR(t) during a selected video sequence were calculated for selected areas of interest (AOI) from the aligned video sequence. ΔR(t) = Rmax-R(t). Thus, ΔR(t) increases with decreasing reflection (increasing blood volume) in the selected AOI. An impedance monitoring system (multiscreen, medis, Germany) was used to measure cardiac parameters (e.g. heart rate, stroke volume) as well as the pulse shape of cardial and peripheral (arm, lower leg) impedance signals simultaneously. Results: The pulsatile reflection component ΔR(t) changes corresponding to the cardiac cycle. ΔR(t) rises suddenly during systole, reaches its maximum after about 32 % of the pulse duration time (RR-interval) and decreases towards the end of the diastole. The pulse shape of ΔR(t) shows a high correspondence to the cardial impedance signal while it is different from the pulse shapes of the peripheral impedance signals. For an entire cardiac cycle, the pulsatile reflection amplitude (PRA) was calculated as PRA = Rmax/Rmin. To assess the spatial distribution, PRA was calculated for different AOIs of (0,8 deg)². PRA is about 8 % at the optic disk (without visible vessels in the AOI), 6 % at 1 deg nasal of the optic disk and 2 % at 7 deg nasal of the macula. At the macula, no PRA could be detected with the present technique. Changes in fundus reflection for both, the pulsatile [ΔR(t)] and the non-pulsatile [Rmax] component induced by provocation of the circulatory system (e.g. Valsalva‘s maneuver) could be correlated with changes in the cardial impedance signal. Conclusions: The reflection of the ocular fundus depends on the cardiac cycle. The simultaneous assessment of ΔR(t) and the impedance signals allows to correlate parameters of ocular microcirculation with cardiac parameters and to distinguish physiologically induced reflection changes from artifacts. More than this, the pulsatile reflection amplitude has to be taken into consideration for quantitative imaging like retinal densitometry.
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