Measurement of the total retinal blood flow using dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes

Abstract

We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray's law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood's velocity scaled linearly with the vessel diameter at higher diameters (> 60 µm), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations.

Keywords: (170.0110) Imaging systems; (170.2655) Functional monitoring and imaging; (170.4460) Ophthalmic optics and devices; (170.4500) Optical coherence tomography; (280.2490) Flow diagnostics.

Figures

Fig. 1

Schematic image of the vessel’s velocity vector v, the beam’s wave vectors k1 and k2 and the angles Δα, β and γ

Fig. 2

Experimental setup with superluminescent diode (SLD), polarization controllers (PC), optical isolator (OI), fiber couplers (FCi), beam displacer (BD), polarizing and non-polarizing beam splitters (PBS and BS, respectively), half-wave plates (λ/2), lenses (L), line cameras (Cam), grey wedge (GW), mirrors (M), hot mirror (HM), scanner (Sc) and Dynamic Vessel Analyzer (DVA)

Fig. 3

Scanning pattern around the ONH; scanning positions denoted by lines in the fundus image (center); corresponding OCT phase images for each scanning position (small circumjacent images; black scale bars correspond to 300µm)

Fig. 4

Beam alignment for superior/inferior vessels, which are scanned horizontally (a) and for nasal/temporal vessels, which are scanned vertically (b)

Fig. 5

Timeline for an artery (left) and a vein (right); the red and white lines represent the phase shifts of the two beams, the green line denotes the resulting phase shift difference between them.

Fig. 6

Top: blood flow velocity v as a function of vessel diameter D for arteries (left) and veins (right). Bottom: log-log plot of blood flow Q over vessel diameter D for arteries (left) and veins (right); dotted lines give the 95% confidence interval. Vessel diameters were determined with OCT for vessels < 65 µm and with DVA for the larger ones.

Fig. 7

Underestimated vessel diameter as determined from the OCT image (inner circle) compared to more accurate diameter measured by the DVA (outer circle)