Relationship of Geographic Altitude with Foveal Avascular Zone Metrics and Vascular Density Values Assessed by OCT Angiography

To evaluate variations in vascular density (VD) and foveal avascular zone (FAZ) metrics in relation to geographic altitude in healthy subjects from 6 Latin American cities. Cross-sectional study. Healthy volunteers from 6 Latin American cities. One hundred eighty-five volunteers were recruited over a 3-month period. The RTVue-XR Avanti system (Optovue, Inc, Fremont, CA) was used along with split-spectrum amplitude-decorrelation angiography (SSADA) software 7.1 to obtain OCT angiography (OCTA) images from fovea-centered 3 × 3-mm2 and 6 × 6-mm2 angioscans for both the superficial and deep capillary plexuses (SCP and DCP, respectively). FAZ measurements were performed in a full retina slab based on the full retina vasculature using OCT angiograms. Analyses of variance were performed for all variables, and P < 0.05 indicated statistical significance. Retinal SCP and DCP VD; FAZ area, perimeter, and parafoveal density at 300 μm (FD-300). Three hundred seventy eyes of 185 participants (71 males and 114 females; mean age, 39.09±15.06 years; age range, 20–80 years) were assessed. The mean VD in the SCP and DCP was 46.94% (±3.11%) and 52.48% (±3.14%), respectively, with 3 × 3-mm2 scans and 50.62% (±3.13%) and 52.87% (±5.5%), respectively, with 6 × 6-mm2 scans. Mean FAZ area, perimeter, and FD-300 were 0.31 (± 0.11 mm2), 2.18 (± 0.43 mm), and 51.44 (± 3.64%), respectively. Mean SCP VD values in 3 × 3-mm2 scans were significantly higher and lower in La Paz and Lima, respectively, compared to those in the other cities (P = 0.001). VD in the 6 × 6 mm2 SCP scans, the DCP (all scans), and FAZ metrics showed no significant differences. VD showed a direct relationship with geographic altitude in SCP 3 × 3-mm2 scans in this group of healthy Hispanic volunteers. These findings indicate that geographic altitude should be accounted for when performing retinal OCTA evaluation of VD values.