Retinal blood flow speed quantification at the capillary level using temporal autocorrelation fitting OCTA [Invited]

Abstract

Optical coherence tomography angiography (OCTA) can visualize vasculature structures, but provides limited information about blood flow speed. Here, we present a second generation variable interscan time analysis (VISTA) OCTA, which evaluates a quantitative surrogate marker for blood flow speed in vasculature. At the capillary level, spatially compiled OCTA and a simple temporal autocorrelation model, <i>ρ</i>(<i>τ</i>) = exp(-<i>ατ</i>), were used to evaluate a temporal autocorrelation decay constant, <i>α</i>, as the blood flow speed marker. A 600 kHz A-scan rate swept-source OCT prototype instrument provides short interscan time OCTA and fine A-scan spacing acquisition, while maintaining multi mm² field of views for human retinal imaging. We demonstrate the cardiac pulsatility and assess repeatability of <i>α</i> measured with VISTA. We show different <i>α</i> for different retinal capillary plexuses in healthy eyes and present representative VISTA OCTA in eyes with diabetic retinopathy.