4D OCTA: Time-resolved OCTA to image chorioretinal hemodynamics in the human eye

Abstract

Purpose : To demonstrate time-resolved optical coherence tomography angiography (OCTA) for imaging cardiac-driven hemodynamics in the chorioretinal vasculature of the human eye.

Methods : Time-resolved OCTA was performed with a swept-source OCT prototype at an 800 kHz A-scan rate using a VCSEL light source at ~1050 nm wavelength. Repeated OCTA volumes of 50-100 B-scans, each consisting of 500 A-scans, covering a 3 mm x 1.5 mm region were acquired at up to 12 volumes per second for 4-5 seconds, resulting in up to 60 sequential OCTA volumes. En face OCTA images generated from the OCTA volumes were compiled into a movie that enabled visualization of spatially localized changes in OCTA signal over time. Time-resolved OCTA imaging was demonstrated in normal subjects as well as patients with diabetes and age-related macular degeneration.

Results : Time-resolved OCTA revealed time dependent variations in OCTA signal from the retinal capillaries, choriocapillaris (CC), and choroidal vessels which correlated with measured heart rate, suggesting a dependency of OCTA signal on cardiac phase. Furthermore, these time-variations appeared as modulations in the visibility of normal and pathologic vasculature structures in the retinal capillaries and CC of normal subjects and patients, with reduced visibility during diastole.

Conclusions : To our knowledge, these results represent the first direct, OCTA-based observation of cardiac-driven modulations in blood flow speed in the human chorioretinal vasculature. These findings have implications for the clinical interpretation of OCTA and for measurements of hemodynamics.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Time-resolved OCTA enables visualization of cardiac-driven OCTA signal time-variations in the retinal vasculature and choriocapillaris (CC) of a normal subject. (A) En face retinal and CC OCTA images extracted from a series of repeated OCTA acquisitions at time points corresponding to diastole (t = 1.33 s) and systole (t = 1.67 s). Dashed white boxes correspond to digitally zoomed ROIs displayed in the panels on the right. (B) OCTA signals, averaged over the entire FOV, exhibit time dependent variations; blue trace corresponds to all retinal vessels; red trace corresponds to retinal capillaries, with larger retinal vessels removed; green trace corresponds to the CC. The pulsatile appearance of the time-variation has a frequency consistent with the subject’s measured heart rate of 70 beats-per-minute.