Author’s Disclosure Block: Annie Lam-Nguyen, none; Anna Polosa, none; Mélanie Hébert, none; Marie-Josée Aubin, none

Abstract Body
Purpose: To review the literature on the value of the electrophysiological testing in patients with birdshot chorioretinopathy (BSCR). Study Design: Systematic review Methods: The EMBASE and Medline databases were screened from inception until June 2024, using relevant search terms, including “birdshot chorioretinopathy”, “birdshot retinochoroidopathy”, “electrophysiological examination”, “electroretinogram”, “electroretinography”, “electrooculogram”. Results: Electrophysiological examination of BSCR patients can achieve earlier diagnosis, better monitoring of the disease and of treatment response. The full-field electroretinogram (ffERG), the light-adapted flicker 30Hz electroretinogram, the multifocal electroretinogram (mfERG) and the pattern ERG (PERG) are most commonly used tests in clinical practice. BSCR patients typically present rod cone dysfunction indicated with a decrease of ffERG amplitudes and an increase in implicit times. A reduction of amplitudes of flicker ERG can also indicate cone dysfunction. Combined with Goldmann or Humphrey visual fields and optical coherence tomography (OCT), these ERG modalities provide an objective and accurate characterization of the extent of retinal damage and visual functional loss even in cases with no apparent fundus abnormalities and stable clinical symptoms. The flicker ERG implicit times, selective dark-adapted b-wave amplitudes as well as specific components of the ffERG known as the oscillatory potentials (OPs) seem to provide better sensitivity and specificity compared to the other parameters of the ffERG and suggest that the initial dysfunction in BSCR occurs within the inner retinal layers (affecting mostly the ON-pathways), but eventually progress to the outer retinal layers if inflammation is left untreated. PERG and mfERG appear to correlate with cystoid macular edema, a common complication in BSCR, and secondary foveal atrophy. Advancements in the field also show that portable ERGs are good alternative screening tools to rapidly assess the visual function in a clinical setting to prompt recognition and treatment of active inflammation. Conclusion: Electrophysiological examination combined with other imaging and clinical modalities is a useful and efficient tool to diagnose and monitor patients with BSCR.