Abstract
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Background: Optic neuritis (ON) and Ischaemic optic neuropathy both present with acute visual loss, and magnetic resonance imaging (MRI) may be helpful in distinguishing the two. Most studies linking MRI findings to clinical features and visual outcome are retrospective, and no Indian study has evaluated MRI in these conditions despite a distinct regional disease profile.
Objectives: To analyse MRI findings in acute ON and ischaemic optic neuropathy, to identify imaging patterns associated with specific clinical and serological presentations, and to correlate MRI findings with visual acuity at six months.
Methods: This prospective observational cohort study was conducted at the Dr. R. P. Centre for Ophthalmic Sciences and the Neurosciences Centre, AIIMS, New Delhi, from January 2025 to March 2026. Patients older than 16 years presenting within one month of a first episode of ON or ischaemic optic neuropathy underwent 3-Tesla contrast-enhanced MRI of the brain and orbits, serum AQP4 (NMO) and MOG antibody testing, and OCT, with follow-up at 2 weeks and 1, 3 and 6 months. Groups were compared using the Mann–Whitney U, Kruskal–Wallis, Wilcoxon signed-rank and Fisher’s exact tests.
Results: Sixty-five patients were enrolled: 54 with ON and 11 with NAION. ON patients were younger (median 30 vs 52 years, p < 0.0001), and NAION was predominantly male (82% vs 39%, p = 0.017). Within ON, 30 (55.6%) were seronegative non-MS, 14 (25.9%) MOG-positive, 6 (11.1%) had an MS pattern on brain MRI and 4 (7.4%) were NMO-positive. Optic nerve enhancement was the commonest finding (47/54, 87%) and involved the intraorbital segment in 46 of 47; more extensive enhancement was associated with worse presenting acuity (p = 0.04) but not with six-month acuity (p = 0.163). Long-segment involvement was seen in 83.3% of antibody-positive versus 27.8% of other patients (OR 13.0, 95% CI 3.1–54.8; p < 0.001; NPV 89.7%), the only feature significant after Bonferroni correction; MRI did not separate NMO from MOG. Both patients with chiasmal involvement had incomplete recovery (median six-month logMAR 1.50 vs 0.00, p = 0.017). At six months, 61.1% of ON patients logMAR 0.00, 27.8% logMAR 0.01-0.03and 11.1% REMAINED > logMAR 0.03; MOG-positive and seronegative groups improved significantly (p = 0.001 and p < 0.001), whereas NAION did not (p = 0.078). In NAION, orbital MRI was normal in 45% and showed optic nerve enhancement in 36%.
Conclusion: Optic nerve enhancement is the commonest MRI sign in acute ON, but its extent reflects presenting severity rather than final outcome. Long-segment involvement is the strongest MRI marker of antibody-positive disease; however, NMO and MOG optic neuritis overlap on imaging, so antibody testing remains essential. Visual prognosis in ON is generally good, chiasmal involvement signals incomplete recovery, andthere may be a overlap between the two groups.
Keywords: Optic neuritis; Non-arteritic anterior ischaemic optic neuropathy; Magnetic resonance imaging; MOG antibody; Aquaporin-4; Visual outcome
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