Assessing total retinal blood flow in diabetic retinopathy using multiplane en face Doppler optical coherence tomography

Abstract

Aim: To assess total retinal blood flow (TRBF) in diabetic retinopathy (DR) using multiplane en face Doppler optical coherence tomography (OCT).

Methods: A 70 kHz spectral-domain OCT system scanned a 2×2 mm area centred at the optic disc of the eyes with DR and healthy participants. The multiplane en face Doppler OCT algorithm generated a three-dimensional volumetric data set consisting of 195 en face planes. The TRBF was calculated from the maximum flow values of each branching retinal vein at an optimised en face plane. DR severity was graded according to the international clinical classification system. The generalised linear model method was used to compare flow values between DR groups and the control group.

Results: A total of 71 eyes from 71 participants were included. Ten eyes were excluded due to poor image quality. The within-visit repeatability of scans was 4.1% (coefficient of variation). There was no significant difference in the TRBF between the healthy (46.7±10.2 µL/min) and mild/moderate non-proliferative DR (44.9±12.6 µL/min) groups. The TRBF in severe non-proliferative DR (39.1±12.6 µL/min) and proliferative DR (28.9±8.85 µL/min) groups were significantly lower (p=0.04 and p<0.0001, respectively) than that of the healthy group. TRBF was correlated with DR disease severity (p<0.0001, linear trend test).

Conclusion: The novel multiplane en face Doppler OCT method provided reliable measurements of TRBF in DR eyes. This may be a useful tool in understanding the pathophysiology of DR.

Keywords: Diabetic retinopathy; imaging; optical coherence tomography; retina; retinal blood flow.

Figure 1

Images from a healthy participant. (A) The volume covers the 2×2 mm area around the optic disc. (B) En face optical coherence tomography reflectance image. (C) Doppler image in three en face planes selected from 195 en face planes in the volumetric data. Red colour means flow into the disk and blue colour means flow out of the disk. The red lines indicated the detected boundaries of veins. (D) The projection of all vein branches. Dashed line is the middle line of disc in order to classify veins as superior and inferior.

Figure 2

Column chart of total retinal blood flow of control group and diabetic retinopathy severity groups. NPDR, non-proliferative diabetic retinopathy; PDR, proliferative diabetic retinopathy. *p<0.05, **p≤0.01, ****p≤0.0001, based on generalised linear model.