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Fabrice Moret, Wolf Lagreze, Charlotte Poloschek, Michael Bach; Mechanisms of retinal venous pulsation inferred from diameter waveforms analysis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4665.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal venous outflow resistance is a candidate element in the etiology of glaucoma. The cardiac pulsation, especially its pressure waveform, can characterize the nature of resistive elements in vascular segments. Expanding on recent data collected to investigate the spontaneous venous pulsation's time of collapse, we examine the pulsation waveform in young healthy subjects and test explanatory hypotheses.
We analyzed fundus movies collected in 12 subjects. Arterial lateral displacement and venous diameter waveforms were measured near the disk on sequences with and without image processing improvement. We then reviewed the various mechanisms proposed so far and assessed each of them with our data. Proposed mechanisms include: the "classical view", a pulse transfer through the microcirculation, a spontaneous pulsation, a Venturi effect, a common adventitial sheath segment, the "constant inflow/variable outflow" hypothesis, and an intracranial pressure interaction.
Venous pulsations show different amplitudes and waveforms, suggesting more than one mechanism at play. None of the previous mechanisms alone fully explains the measured waveforms. We propose two mechanisms: 1. For waveforms showing a damped-like version of the arterial pressure: initially (and well-established), the pulsation of the choroidal volume governed by a Windkessel effect leads to an intraocular pressure pulsation of similar waveform, then this pulsation is transferred to the retinal circulation upstream of the measurement sites. 2. For venous diameter waveforms matching the arterial pressure waveforms: the pressure pulsation of the central retinal artery is transferred to the central retinal vein in a non-extensible common adventitial sheath segment in the optic nerve.
The waveform of the retinal venous pulsation obtained from fundus movies informs on the nature of the venous outflow resistance in ways not matched by an analysis of the amplitude alone. It would now be of interest as of whether quantitative changes are observed in glaucoma.
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