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

Abstract

Purpose: 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.

Design: Cross-sectional study.

Participants: Healthy volunteers from 6 Latin American cities.

Methods: 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.

Main outcome measures: Retinal SCP and DCP VD; FAZ area, perimeter, and parafoveal density at 300 μm (FD-300).

Results: 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.

Conclusions: 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.