Abstract
Laser Doppler holography was introduced as a full-field imaging technique to measure blood flow in the retina and choroid with an as yet unrivaled temporal resolution. We here investigate separating the different contributions to the power Doppler signal in order to isolate the flow waveforms of vessels in the posterior pole of the human eye. Distinct flow behaviors are found in retinal arteries and veins with seemingly interrelated waveforms. We demonstrate a full field mapping of the local resistivity index, and the possibility to perform unambiguous identification of retinal arteries and veins on the basis of their systolodiastolic variations. Finally we investigate the arterial flow waveforms in the retina and choroid and find synchronous and similar waveforms, although with a lower pulsatility in choroidal arteries. This work demonstrates the potential held by laser Doppler holography to study ocular hemodynamics in healthy and diseased eyes.
Highlights
The ocular circulation is of major interest for the study of increasingly prevalent diseases such as diabetic retinopathy, glaucoma, and hypertension
The blood flow supply to the retina is carried out by two independent vasculatures originating from the ophthalmic artery that differ in organization and function
The retinal vessels are branches of the central retinal artery and supply the neural retina and the prelaminar region of the optic nerve head (ONH), whereas the choroidal vessels originate from the posterior ciliary arteries (PCAs) which supply the photoreceptor and epithelial cells
Summary
The ocular circulation is of major interest for the study of increasingly prevalent diseases such as diabetic retinopathy, glaucoma, and hypertension. The irruption and development of optical coherence tomography (OCT) and subsequently of OCT-angiography (OCT-A) has allowed for a comprehensive study of the relationship between diseases affecting the eye and the fundus vasculature anatomy by its ability to resolve the retinal microvasculature [1, 2], and the thickness of the vascular choroidal compartment [3] Another approach to investigate the ocular circulation is the study of the blood flow dynamics, which requires a temporal resolution currently not in the reach of present day OCT-A systems [4]. A wave decomposition analysis of ultrasonic Doppler flow velocity waveforms has proven able to identify microvascular hemodynamic abnormalities in the ophthalmic and carotid artery in cases of diabetic retinopathy [17] Another factor to take into consideration for the shape and amplitude of the arterial flow profile is the site of measurement of the waveform. This flow waveform is all the more interesting as measurements of an impaired pulsatile arterial flow could provide more information regarding potential microvascular damages provoked by an overly high perfusion pressure
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