  Optical coherence tomography angiography (OCTA) can non-invasively image the
eye's circulatory system. In order to reliably characterize the retinal
vasculature, there is a need to automatically extract quantitative metrics from
these images. The calculation of such biomarkers requires a precise semantic
segmentation of the blood vessels. However, deep-learning-based methods for
segmentation mostly rely on supervised training with voxel-level annotations,
which are costly to obtain. In this work, we present a pipeline to synthesize
large amounts of realistic OCTA images with intrinsically matching ground truth
labels; thereby obviating the need for manual annotation of training data. Our
proposed method is based on two novel components: 1) a physiology-based
simulation that models the various retinal vascular plexuses and 2) a suite of
physics-based image augmentations that emulate the OCTA image acquisition
process including typical artifacts. In extensive benchmarking experiments, we
demonstrate the utility of our synthetic data by successfully training retinal
vessel segmentation algorithms. Encouraged by our method's competitive
quantitative and superior qualitative performance, we believe that it
constitutes a versatile tool to advance the quantitative analysis of OCTA
images.
