Repeatability and Reproducibility of Total Retinal Blood Flow Measurements Using Bi-Directional Doppler OCT

To investigate the repeatability and reproducibility of total retinal blood flow measurements using a custom-built dual-beam bidirectional Doppler optical coherence tomography (OCT) system in healthy subjects.

Repeatability and reproducibility were analyzed in 10 and 34 healthy subjects, respectively. For repeatability, measurements were taken twice within 30 minutes, for reproducibility, twice within two to five weeks. Two analysis approaches were compared for calculation of absolute blood velocities: a previously published approach resulting in values for total arterial (Q_A,abs) and total venous blood flow (Q_V,abs) and a novel approach taking into account that there is a fixed relation between the phase shift in the two OCT channels (Q_A,new, Q_V,new). Repeatability and reproducibility were quantified using intraclass correlation coefficients (ICCs).

For Q_A,abs and Q_V,abs, ICC values between 0.78 and 0.84 were obtained. Q_A,new and Q_V,new values revealed better repeatability and reproducibility as compared to the convential appoach. Repeatability ICCs for Q_A,new and Q_V,new were between 0.91 and 0.93, and reproducibility ICCs were between 0.87 and 0.91 indicating excellent reproducibility. Good agreement was observed between total retinal blood flow values as measured from retinal arteries and retinal veins.

Measurement of total retinal blood flow using dual-beam Doppler OCT shows excellent reproducibility, which can further be improved by using a novel algorithm for calculating blood velocities in retinal vessels.

Our data indicate that dual-beam Doppler OCT can be used for longitudinal studies. Hence, quantitative retinal blood flow may be established as a biomarker for progression vascular eye diseases.