The identification of aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) antibodies (Abs) has transformed greatly the management of acute ON. Indeed, these auto-antibodies related disorders require different therapeutic management strategies than multiple sclerosis (MS), including early initiation of plasma exchange and steroids, maintenance oral corticosteroids therapy, or use of immunosuppressive agents as first line therapy (Ramanathan et al., 2018 Feb, Rode et al., 2022 Dec 13, Zéphir et al., 2015 Oct, Bonnan et al., 2018 Apr). However, auto-antibodies status is not available immediately, delaying the diagnosis with a risk of poor recovery.

Several cross sectional studies have described clinical and radiological features of the different ON aetiologies (Bennett et al., 2023 Jan). Nevertheless the prevalence of the ON aetiologies being different, it remains unclear what are the most useful features of an acute ON for distinguishing the different aetiologies in a real life setting.

Optical coherence tomography (OCT) is a non-invasive imaging technique that measure the thickness of the retinal layers, in particular the peripapillary retinal nerve fibre layer (pRNFL) and the composite macular ganglion cell and inner plexiform layers (mGCIPL). Several studies have recently analysed the potential role of OCT imaging to discriminate the different causes of ON (review in (Filippatou et al., 2020 Oct 8)). However, many previous OCT studies of ON were cross-sectional, and longitudinal studies are scarce.

The aim of the present monocentric prospective study was to determine the performance of clinical data, ophthalmological examination (including OCT), CSF and magnetic resonance images (MRI) results at baseline to discriminate between the different causes of ON. Visual function and OCT results at 1 and 12 months after ON were compared among optic neuritis aetiologies.