Measuring choriocapillaris blood flow with laser Doppler optical coherence tomography

We report on using a laser Doppler processing of Fourier-domain optical coherence tomography (OCT) data for the assessment of pulsatile blood flow in the choriocapillaris. Signal fluctuations in B-scans recorded at 2 kHz were analyzed by Fourier transform to extract blood flow information. The spectral broadening of light backscattered by the choriocapillaris was used to derive a choriocapillaris flow velocity index in physical units, with sufficient temporal resolution to capture heartbeat-induced variations. Furthermore, the asymmetry in the spectral broadening enabled us to determine the axial direction of blood flow with high sensitivity, allowing for the detection of flow orientation in retinal capillaries. This approach is promising as it can be directly implemented on widely available fast-scanning Fourier-domain OCT instruments.