Macular Vascular Flow Area and Vascular Density in Healthy Population Using Optical Coherence Tomography Angiography

We read with interest the paper from Coscas et al.¹ regarding the normative data for vascular density in superficial and deep capillary plexuses of healthy adults assessed by optical coherence tomography angiography (OCT-A). 

The authors state that using the AngioVue OCT-A system (Optovue, Inc., Fremont, CA, USA), the total vascular density in superficial capillary plexus in healthy adults is 52.58 ± 3.22% and for the deep vascular density is 57.87 ± 2.82%. 

Optical coherence tomography angiography technology has some major limitations in clinical practice nowadays: variable segmentation, motion artifact, and project artifact.² We must take into account that OCT-A manufacturers utilize various algorithms for acquisition, segmentation, and projection removal for their own system. 

The University Hospital of La Candelaria Department of Ophthalmology, Spain, performed an analysis related to the macular vascular flow area and vascular density in a healthy population using the OCT-A Nidek Advance system (Nidek, Aichi, Japan), partially presented at the 5th International SIRCOVA Meeting (July 1 and 2, 2016, Valencia, Spain).³ 

We analyzed 18 patients (36 eyes), with a 41.58% male and a 61.42% female composition. Mean age was 48.21 ± 10.76 (range 33–65) years, and spherical equivalent was 0.59 ± 1.9 diopters. A 3 × 3-mm area, centered on the fovea, was scanned for all the study subjects in both eyes. Automated measurement of the vessel flow area and of the density of vessel flow was performed as well in the superficial and in the deep plexus using the Navis-EX software built in into the Nidek OCT-A. Our results are shown in the Table. 

Table

 

Vessel Flow Area and Density of Vessel Flow of the Superficial and Deep Plexus in Healthy Population

 

In our opinion there is no standard of acquisition, vascular plexus segmentation, and automated measurement among the different OCT-A manufacturers, so we cannot state normative data for vascular density unless we specify a particular OCT-A system. All automated measurement values in OCT-A systems should be considered in relation to the OCT-A system we are using.