Normative Perfusion Indices in the Emmetropic Nondiabetic and Healthy Highly Myopic Adult Population

Reference values of optical coherence tomography angiography metrics vary according to the device used to measure them and even based on the software on the same device. There might exist measurement differences between different maps within the same device: Variables such as age, gender, and signal strength might induce changes in the measurement outputs.

This chapter deals with the values of vessel length and vessel area densities, and foveal avascular zone values of healthy emmetropic people via the 3 × 3 mm map used in the most common equipment that are available commercially. The text includes metrics of the parafovea and fovea at the superficial, intermediate, and deep capillary plexuses. These measurements corresponded to the adult non-diabetic population and were distributed as center (foveal), inner (parafoveal) and full (whole map) densities, depending on the evaluated region, according to densities in the foveal, parafoveal, and whole map measurements. Metrics of the parafovea by subfield were also included. We also report current cut-off values that have been proposed as normality references in some variables. Values for the remaining metrics and devices can later be proposed. We dedicate a special section to non-diabetic patients with high myopia without pathology, which includes the same metrics as in emmetropic patients. The evaluation of perfusion indices benefits from the simultaneous measurement of metrics as well as regional evaluation. The signal strength is a key variable to consider.

Keywords: Area, Deep capillary plexus, Emmetropia, Foveal avascular zone, Middle capillary plexus, Myopia, Perimeter, Superficial capillary plexus, Vessel area density, Vessel length density.