What are the clinical features and treatment of optic neuritis?

Clinical Features of Optic Neuritis

Cardinal Clinical Presentation

Optic neuritis classically presents with the triad of subacute visual loss developing over hours to days, periocular pain worsening with eye movement, and red-green color desaturation (dyschromatopsia). 1

Visual Symptoms

• Visual field defects, particularly central scotomas, are characteristic and may persist permanently despite treatment 1
• Visual impairment develops subacutely over hours to days, distinguishing it from acute vascular events 1
• Photophobia commonly accompanies the acute presentation and may persist chronically 2, 1
• Contrast sensitivity, color vision, and visual field deficits often remain impaired even after visual acuity recovers 3

Pain Characteristics

• Periocular pain that worsens with eye movement is present in the majority of cases 1
• Pain typically precedes or accompanies visual loss 3

Physical Examination Findings

Pupillary Abnormalities

• In unilateral optic neuritis, the direct pupillary light reflex is weaker in the affected eye (relative afferent pupillary defect) 4

Optic Disc Appearance

• One-third of patients present with mild optic disc edema (papillitis) 4
• Two-thirds have a normal-appearing disc initially (retrobulbar optic neuritis) 4
• Chronic cases demonstrate optic nerve atrophy or pallor 1

Diagnostic Confirmation

MRI Findings

• T1-weighted post-contrast images with fat suppression identify abnormal optic nerve enhancement in 95% of optic neuritis cases 5, 6
• Typical acute lesions show T2 hyperintensity, optic nerve swelling, and contrast enhancement 1, 6
• Coronal fat-suppressed T2-weighted sequences are optimal for visualizing optic nerve lesions 1
• MRI of both head and orbits with and without IV contrast is the primary diagnostic study 5, 6

Neurophysiological Testing

• Delayed visual evoked potentials (VEPs) confirm optic nerve dysfunction with slowed conduction 1
• VEPs provide objective evidence even when imaging is equivocal 1

Optical Coherence Tomography

• Retinal nerve fiber layer (RNFL) thinning provides evidence of optic nerve damage 1
• OCT documents both acute changes and chronic sequelae 1

Red Flags for Atypical Optic Neuritis

The following features mandate urgent serologic testing for AQP4-IgG and MOG-IgG to identify neuromyelitis optica spectrum disorder (NMOSD) or MOG-antibody disease (MOGAD): 6

• Bilateral simultaneous involvement - strongly suggests NMOSD or MOGAD rather than MS 1, 6
• Posterior optic nerve involvement extending to the chiasm 1, 6
• Long optic nerve lesions on MRI 1, 6
• Severe vision loss with poor recovery after steroids or steroid dependence 6
• Prominent optic disc edema 6
• Soft tissue enhancement extrinsic to the nerve (affecting orbit, orbital apex, or cavernous sinus) - indicates MOG-IgG disease, granulomatous disease, tumor, or infection rather than MS 6

Multiple Sclerosis Risk Stratification

High-Risk Features

• The presence of even one clinically silent T2 hyperintense brain lesion on MRI is highly associated with eventual MS diagnosis 5, 2, 1
• CSF oligoclonal bands combined with brain MRI lesions dramatically reduce the likelihood of monophasic illness 5, 1
• Patients with brain MRI lesions have a hazard ratio of 5.1 for MS conversion with 1-3 lesions and 11.3 with ≥10 lesions 5

Low-Risk Features

• Absence of brain lesions on initial MRI strongly predicts a monophasic illness with lower MS risk 2, 1
• Negative brain MRI suggests non-MS etiology 6

Visual Prognosis

Typical Optic Neuritis (MS-Associated or Idiopathic)

• Visual disturbance resolves in 95% of cases 4
• Recovery of high-contrast visual acuity is common 7
• Residual deficits in contrast sensitivity, binocular vision, and motion perception may impair quality of life 7

Atypical Optic Neuritis

• SLE-related optic neuritis carries particularly poor visual prognosis, with only 30% maintaining visual acuity greater than 20/25 2, 6
• NMOSD-associated optic neuritis results in more severe vision loss and poorer recovery than MS-related cases 2, 6, 7
• MOG-IgG positive patients may have more severe optic nerve atrophy than typical MS-associated optic neuritis 7
• Bilateral simultaneous involvement generally portends worse visual outcomes 2, 6

Treatment Considerations

Acute Treatment

• High-dose intravenous methylprednisolone speeds recovery but does not improve final visual outcome 3, 4
• Early treatment (within hours to days) is associated with better outcomes, particularly in severe cases 2
• Treatment delay beyond 2 weeks is an unfavorable prognostic factor 2, 6

Critical FDA Warning

• The use of oral corticosteroids is not recommended in the treatment of optic neuritis and may lead to an increase in the risk of new episodes 8, 9
• Oral prednisolone alone is contraindicated due to increased risk of recurrence 3

Maintenance Therapy for Atypical Cases

• Relapses occur in 50-60% during corticosteroid dose reduction in NMOSD and MOGAD cases 2, 6
• Maintenance immunosuppressive therapy is essential for preventing relapses in NMOSD and certain autoimmune etiologies 2

Common Pitfalls to Avoid

• Do not use oral prednisone as monotherapy - this increases recurrence risk per FDA labeling and clinical trials 8, 9, 3
• Do not assume unilateral presentation excludes NMOSD or MOGAD - obtain antibody testing if any red flags present 6
• Do not skip brain MRI even in isolated optic neuritis - it is critical for MS risk stratification 1
• Do not delay antibody testing (AQP4-IgG, MOG-IgG) when bilateral involvement or other red flags are present - treatment approaches differ fundamentally 6