Quantification of Retinal Blood Flow Using Doppler OCT with a PLEX TM Elite 9000

Abstract

Purpose : Doppler OCT is a promising method to quantify retinal blood flow. Various studies have shown that for Glaucoma patients the amount of blood flow is highly correlated to visual field loss and therefore can be used as an indicator of the disease and to monitor its development. Furthermore, with the development of OCT Angiography, tracking and motion correction techniques have improved likely leading to improved Doppler OCT measurements. This poster presents Doppler-OCT results using active tracking.

Methods : For data acquisition, a circular OCT scan with a radius of 2.1 mm and 13200 A-Scans is acquired around the ONH with a PLEX TM Elite 9000 (ZEISS, Dublin, CA). The circular scan is repeated 22 times. This allows averaging of the TRBF over approximately three cardiac cycles. The intensity and phase data are both recorded and used to calculate the phase shift and therefore the Doppler shift of light scattered by corpuscles. With the knowledge of the angle between the particular blood vessel and the light beam (Doppler angle) the blood flow and its velocity can be calculated. The retinal blood flow is calculated through a fully automated algorithm which includes angle measurements and blood vessel detection.

Results : The data measured over a time period of 2.6 s is shown in Figure 1. In the upper image of Figure 1, the calculated Doppler phase shift for one moment in time is shown. In the lower picture, the calculated blood flow velocity for 18 blood vessels is illustrated. According to the vessel flow direction, the velocity is positive or negative which corresponds to blood flowing into or out of the ONH respectively. The average velocity of the six major vessels is 17.04 mm/s thereby their average blood flow ranges from 0.85 µl/min to 5.5 µl/min. In Figure 2, the calculated blood flow for two close-by vessels is plotted over time. It can be clearly seen that it follows the cardiac cycle which is determined to be approximately T_C = 750 ms.

Conclusions : The results show blood flow measurements on a PLEX TM Elite 9000 using Doppler OCT. The period, shape, and flow speeds during the cardiac cycle matches with previous literature.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Figure 1: Doppler-OCT circular scan around ONH. The upper picture shows the calculated blood flow velocity and the lower picture illustrates the Doppler phase shift.

 

Figure 2: Plot of the blood flow of one vessel over time. The cardiac cycle is approximately T_C = 750 ms.