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M. Johnstone, R. Stegmann, E. Martin, A. Jamil; Pulsatile Circumferential Aqueous Flow Into Schlemm’s Canal (SC) Is Synchronous With the Cardiac Pulse. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4855.
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To describe and characterize pulsatile aqueous flow into SC.
Three African patients without glaucoma undergoing cataract surgery. Gonioscopy with goniolens compression of aqueous veins to reflux blood into SC. Microscope (80 power). High resolution videography at 30 frames per second. Micrometer scale. Still frame analysis. SC blood provides background for visualization of clear aqueous entering SC. Pulse-induced head movements (described in many MRI-related reports) cause a consistent frame artifact in individual video frames which provides an embedded optical signal permitting timing of cardiac pulse wave arrival.
In 3 patients pulsatile aqueous flow into SC was identified by a pulsatile aqueous wave that propagated circumferentially in SC as it mixed with blood. Aqueous wave propagation originated in a funnel-shaped area. Subsequent narrowing of the funnel-shaped area was followed by propagation of the aqueous wave from the apex of the funnel into a wave confined to a cylindrical shape that passed circumferentially in SC. Aqueous wave propagation through the cylindrically-shaped area was followed by aqueous ejection into SC along a circumferential path indentified by whirling vortices of aqueous and blood. In one patient twenty sequential aqueous waves were identified in 16 seconds. Aqueous wave arrival time was identified at 3 specific points (A,B,C). Arrival time of the aqueous wave at each point was plotted against the cardiac pulse wave arrival. Arrival time of the aqueous pulse wave at points A, B,C correlated with timing of the cardiac pulse induced head movements and the correlation was highly significant;( R2 = 0.99, p < 0.0001) at each point.
Pulsatile circumferential aqueous flow into SC is identified that is synchronous with the cardiac pulse.
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