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Abstract
Assessment of retinal blood flow inside the optic nerve head (ONH) and the peripapillary area is an important task in retinal imaging. For this purpose, an experimental binocular video ophthalmoscope that acquires precisely synchronized video sequences of the optic nerve head and peripapillary area from both eyes has been previously developed. It enables to compare specific characteristics of both eyes and efficiently detect the eye asymmetry. In this paper, we describe a novel methodology for the analysis of acquired video data using a photoplethysmographic approach. We describe and calculate the pulsatile attenuation amplitude (PAA) spatial map, which quantifies the maximum relative change of blood volume during a cardiac cycle using a frequency domain approach. We also describe in detail the origin of PAA maps from the fundamental (the first) and the second harmonic component of the pulsatile signal, and we compare the results obtained by time-based and frequency-based approaches. In several cases, we show the advantages and possibilities of this device and the appropriate image analysis approach - fast measurement and comparison of blood flow characteristics of both eyes at a glance, the robustness of this approach, and the possibility of easy detection of asymmetry.
Highlights
The retina is the only human tissue allowing direct noninvasive imaging of the microvascular circulation and central nervous system
New functional imaging approaches - optical coherence tomographic angiography (OCT-A) or laser speckle flowgraphy (LSFG) are being developed to find clinically relevant parameters. These technologies have become important in many research and clinical setups for retinal and systemic cardiovascular disease assessment as they enable the measurement of functional biomarkers
The lower optic nerve head (ONH) blood flow reduction was confirmed by several papers using different OCT-A and LSFG modality, e.g., [5,19,20] and we showed lower ONH pulsatile attenuation amplitude (PAA) values for glaucoma subjects in our previous study [11]
Summary
The retina is the only human tissue allowing direct noninvasive imaging of the microvascular circulation and central nervous system. New functional imaging approaches - optical coherence tomographic angiography (OCT-A) or laser speckle flowgraphy (LSFG) are being developed to find clinically relevant parameters These technologies have become important in many research and clinical setups for retinal and systemic cardiovascular disease assessment as they enable the measurement of functional biomarkers (e.g., papers related to OCT-A [2,3] and LSFG [4,5]). Recent development in this field has provided solutions for precise blood velocity quantification using multiple beams to solve the problem with unknown Doppler angle [7]. Another new promising technology based on Doppler holography has been introduced by
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