Optical coherence tomography angiography in birdshot chorioretinopathy

Purpose: To describe the retinal vascular changes in birdshot chorioretinopathy (BSCR) using optical coherence tomography angiography (OCTA) and to compare them with changes in macular thickness. Methods: In this multicenter study, patients with a diagnosis of BSCR and a positive HLA-A29 underwent fluorescein angiography, spectral domain optical coherence tomography (SD-OCT), and OCTA. The foveal avascular zone (FAZ) and the area of capillary non-perfusion were manually measured by two examiners in fluorescein angiography (FA) and 3 × 3-mm OCTA images of the superficial retinal layer. These measurements were compared to central retinal thickness. To calculate normal capillary density, we collected data from 22 controls who had OCTA performed on one visit only. Results: A total of 44 eyes with BSCR were enrolled. The mean automated parafoveal superficial capillary density in BSCR eyes was 0.47 ± 0.03. The differences between the foveal capillary density of BSCR patients and healthy subjects were statistically significant (P < 0.001). The mean area of FAZ manually measured on the 3 × 3 mm unsegmented OCTA images was larger in eyes with BSCR (1.34 ± 0.41 mm2; P < 0.0001). Measurement of FAZ area showed good interobserver (κ 0.88) and intraobserver repeatability (κ 0.79) on OCTA images. The intraclass correlation coefficient for FAZ measurements on FA between the two observers was 0.48. The OCT retinal thickness maps of all BSCR eyes demonstrated statistically significant thinning compared to those of control subjects (P < 0.01). Conclusion: Our study demonstrates the potential contribution of OCTA as a new non-invasive imaging technology that monitors disease activity in BSCR patients.