Optic neuritis is an important cause of acute or subacute visual loss. In clinical practice, optic neuritis must often be distinguished from other optic neuropathies, retinal diseases, anterior-segment or ocular media disorders, non-organic visual loss, and other mimics. The 2022 International Criteria for Optic Neuritis were developed to standardize the diagnosis of optic neuritis, but their performance in Chinese clinical settings, where aquaporin-4 immunoglobulin G-positive and myelin oligodendrocyte glycoprotein immunoglobulin G-positive optic neuritis are relatively common, remains uncertain. This multicenter prospective observational study is enrolling patients with acute or subacute visual loss in whom optic neuritis is included in the differential diagnosis. The study is designed to evaluate the diagnostic performance of the 2022 International Criteria for Optic Neuritis alone and with an antibody-stratified adjunct. The index classifications will be compared with an expert-adjudicated reference-standard diagnosis. No experimental treatment is assigned by the study. All diagnostic tests and treatments are determined by the treating clinicians according to routine clinical care. Study data are collected using a structured protocol-defined case report form.
Inclusion Criteria: 1. Individuals presenting with a new acute or subacute episode of visual loss or optic nerve-related visual dysfunction in one or both eyes, for whom optic neuritis is considered a reasonable differential diagnosis by the treating clinical team at the initial clinical assessment and before final diagnostic adjudication. 2. Symptom onset of the current episode within 90 days before enrollment. Exclusion Criteria: 1\. The participant has previously been enrolled in this study. Each participant may be enrolled only once. A history of optic neuritis or recurrent optic neuropathy before the current episode is not an exclusion criterion.