  Angiography by Optical Coherence Tomography is a non-invasive retinal imaging
modality of recent appearance that allows the visualization of the vascular
structure at predefined depths based on the detection of the blood movement.
OCT-A images constitute a suitable scenario to analyse the retinal vascular
properties of regions of interest, measuring the characteristics of the foveal
vascular and avascular zones. Extracted parameters of this region can be used
as prognostic factors that determine if the patient suffers from certain
pathologies, indicating the associated pathological degree. The manual
extraction of these biomedical parameters is a long, tedious and subjective
process, introducing a significant intra and inter-expert variability, which
penalizes the utility of the measurements. In addition, the absence of tools
that automatically facilitate these calculations encourages the creation of
computer-aided diagnosis frameworks that ease the doctor's work, increasing
their productivity and making viable the use of this type of vascular
biomarkers.
  We propose a fully automatic system that identifies and precisely segments
the region of the foveal avascular zone (FAZ) using a novel ophthalmological
image modality as is OCT-A. The system combines different image processing
techniques to firstly identify the region where the FAZ is contained and,
secondly, proceed with the extraction of its precise contour. The system was
validated using a representative set of 168 OCT-A images, providing accurate
results with the best correlation with the manual measurements of two experts
clinician of 0.93 as well as a Jaccard's index of 0.82 of the best experimental
case. This tool provides an accurate FAZ measurement with the desired
objectivity and reproducibility, being very useful for the analysis of relevant
vascular diseases through the study of the retinal microcirculation.
