In neuroinflammatory diseases of the central nervous system (CNS) such as multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD) and anti-MOG antibody-associated disorders (MOGAD), neuronal degeneration is the consequence of inflammatory and demyelinating lesions in the brain, optic nerve and spinal cord. Both white and grey matter are systematically affected. Lesions of the perivascular spaces containing cerebrospinal fluid (CSF) and meningeal inflammation seem to play an important role in the pathophysiology of these neuroinflammatory diseases. Currently, the interrelation of all these aspects is not clearly established in the pathophysiology of these diseases. In order to better understand the mechanisms that lead to and underlie the clinical disability of patients with these diseases, we need in vivo study models that allow the in-depth study of the neurodegenerative process and the identification of its causes. In this perspective, we make the hypothesis that the visual pathways model is very relevant to measure neuro-axonal loss and to explore the different mechanisms involved in neurodegeneration during MS and other CNS demyelinating diseases. Researchers have at their disposal many tools that allow them to analyse and quantify the neurodegenerative process in a reproducible and very precise manner from a structural and functional point of view, while taking into account possible vascular involvement (MRI, optical coherence tomography - angiography, etc…).

Inclusion Criteria:

• - Male or female
• Aged between 18 and 65 years
• Presenting a clinical picture of optic neuritis for less than 4 weeks, confirmed by neuro-ophthalmological assessment
• Patient having given written consent to participate in the study
• Patient with social insurance
• Patient willing to comply with all study procedures and duration

Exclusion Criteria:

• - history of optic neuritis on the same side as the recent episode for which the patient is being treated
• history of retinal pathology (retinal detachment, glaucoma, retinopathies, retinal surgery)
• diabetes
• chronic alcohol intoxication
• contraindications to MRI
• pregnant women
• persons under protective supervision (ex : guardianship)
• minors
• persons deprived of their liberty
• administrative reasons: inability to receive informed information, inability to participate in the entire study, lack of social security coverage, refusal to sign consent

A history of pre-existing CNS inflammatory demyelinating disease is not a criterion for non-inclusion.

Patients presenting an episode of acute optic neuritis with the objective of better understanding the pathophysiology of CNS inflammatory diseases and identifying prognostic biomarkers in imaging