Retinal Arteriole Pulse Waveform Analysis Using a Fully-Automated Doppler Optical Coherence Tomography Flowmeter: a Pilot Study

Abstract

Purpose: To evaluate the repeatability and reproducibility of the measurement of retinal arteriole pulse waveforms using a novel fully-automated Doppler optical coherence tomography (DOCT) flowmeter in healthy subjects.

Methods: Twenty eyes of 20 healthy subjects were included to test the intrasession repeatability of pulse waveform analysis. DOCT measurements were performed based on a newly developed instantaneous Doppler angle measurement method. Upstroke time (UT), which is the time from the minimum to the maximum retinal blood velocity, and the resistance index (RI) of the retinal arteriole pulse waveform were measured. Coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) were calculated. Interdevice reproducibility between two instruments was assessed in five eyes of five subjects.

Results: The mean UT was 130.3 ms (range, 110.1-152.1 ms), and the mean RI was 0.66 (range, 0.51-0.82). The respective ICCs of UT and the RI for the intrasession repeatability of assessment were 0.87 and 0.78. The respective CVs of UT and the RI were 6.6 ± 3.3% and 4.7 ± 2.1%. Regarding interdevice reproducibility, there were no significant differences between the measurements derived from the instruments (P > 0.05).

Conclusions: Pulse waveform measurement in retinal arterioles using a fully-automated DOCT flowmeter exhibited good repeatability and interdevice reproducibility.

Translational relevance: The above-described improved DOCT flowmeter system provides reasonably repeatable measurements of retinal arteriole pulse waveforms, potentially facilitating systemic-circulation abnormality monitoring. The examination of the circulation with the novel device can be potentially useful for evaluating systemic circulation.

Keywords: Doppler OCT; blood flow; optical coherence tomography; pulse waveform; retinal artery.

Figure 1

Schematic diagram of real-time Doppler angle measurement. (A) The two alternative scan positions set as scans A and B, which are located around one-disc diameter away from the optic disc center of the inferior-temporal vessel. The scan separation distance, Δy, was determined to be 100 μm. Two example phase images showing the identification of vessels separated in Δz. (B) Forty-five repeated alternate scans for both pulse waveform measurement and Doppler angle θ calculation.

Figure 2

Bench test result of the real-time Doppler angle measurement method. (A) Measured Doppler angle (dots) and linear regression line (dotted line) in left axis and correction coefficient (broken line) measured over a 2-s period in right axis. (B) Calculated velocity over a 2-s period with and without Doppler angle compensation.

Figure 3

Three repeated measurement results of the retinal arteriole pulse waveform. , , and UT were determined from the one pulse waveform extracted from Doppler OCT measurement.

Figure 4

Retinal arteriole pulse waveforms of different scanning positions and different vessels. (A) Color fundus image and scanning location of Doppler OCT imaging in superior-temporal (scan 1) in the right eye, (B) superior-temporal (scan 2, 3), and inferior-temporal (scan 4) arterioles in the left eye of the same subject. (C) Four measurement results of retinal arteriole pulse waveform in DOCT imaging.