Non-invasive biomarkers for close activity monitoring in birdshot chorioretinitis: Optical coherence tomography angiography and beyond.

Abstract

The purpose of the study was to identify non-invasive imaging biomarkers potentially useful for close activity monitoring in birdshot chorioretinitis (BSCR). Cross-sectional study of BSCR eyes included as per Levinson's and/or SUN criteria. Eyes were blindly classified into active or inactive groups per clinical inflammatory parameters, ultra-widefield (UWF) pseudocolour images, UWF fluorescein angiography (FA) and macular optical coherence tomography (OCT) cube. Qualitative and quantitative OCT and OCT-angiography (OCT-A) parameters at the fundus, superonasal and inferonasal fields were compared between active and inactive eyes. Thirty consecutive BSCR patients (60 eyes) were analysed. 28 eyes (46.66%) were from women and the overall mean age was 59.7 ± 12.3 years. Active eyes showed an abnormal retinal thickening at inferonasal field (nasal retinal thickness) and a higher averaged thickened retinal index (ATRI) (72.36 active vs. 20.12 inactive, p < 0.0001). A significant moderate correlation was observed between ATRI and FA scores (r = 0.259, p = 0.022). Macular vascular loops were more frequent in the superficial vascular plexus of OCT-A in the active eyes (p = 0.028). The vascular perfusion index tended to be higher in all subfields of active eyes but did not reach statistical significance. Multimodal imaging could be key to discerning activity in BSCR eyes. Higher ATRI and the presence of vascular loops in the superficial plexus are potential non-invasive activity biomarkers for the close monitoring of BSCR.