Foveal Avascular Zone is Larger in the Superficial Retinal Layer; an Optical Coherence Tomography Angiography Study Comparing Two Spectral Domain Devices

Purpose: To evaluate the size of foveal avascular zone (FAZ) area in the superficial and deep retinal layers using two different spectral-domain optical coherence tomography angiography (OCTA) devices. Methods: A cross-sectional comparative study was conducted to obtain macular OCTA images from healthy subjects using Optovue RTVue XR Avanti (Optovue, Inc, Fremont, CA) and Spectralis HRA+OCTA (Heidelberg Engineering, Heidelberg, Germany). Two independent trained graders measured the FAZ area using automated slab segmentation. The FAZ area in superficial and deep retinal layers was compared. Results: Twenty-three eyes of 23 subjects were included. The graders agreement was excellent (> 0.86) for all measurements. The mean FAZ area was significantly larger at the superficial retinal layer compared to the deep retinal layer on both devices (0.31±0.08 mm2 versus 0.26±0.08 mm2 in Optovue and 0.55±0.16 mm2 versus 0.36±0.13 mm2 in Spectralis, both P < 0.001). The mean FAZ area was significantly larger at both superficial and deep retinal layers in Spectralis than in Optovue measurements (P< 0.001 for both). Conclusion: In contrast to previous reports, the size of FAZ was larger in superficial than in deep retinal layers using the updated software versions. The measurements from different devices cannot be used interchangeably.