9. Typical Optic Neuritis

What are the three most common optic neuropathies?

• Glaucoma

• Typical optic neuritis

• NA-AION (non-arteritic anterior ischemic optic neuropathy)

What is the key clinical approach when evaluating optic neuropathy?

• First, determine if it is one of the “big 3”

• If NOT (and no trauma):
  → Assume atypical optic neuropathy
  → Requires urgent further workup

What is the typical presentation of inflammatory optic neuritis?

• Acute vision loss (hours → days)

• Improves over weeks

• Unilateral episode (most common)

• Pain with eye movement

What visual function deficits are seen in typical optic neuritis?

• Decreased visual acuity

• Reduced color vision (classic early sign)

• Decreased contrast sensitivity

• Visual field defects

How do you clinically distinguish typical optic neuritis from atypical optic neuritis?

Typical (MS):

• Unilateral

• Pain with eye movement

• Improves in weeks

• Moderate severity

Atypical:

• Bilateral / severe

• Painless or persistent

• Poor recovery

• Unusual age or course

How is optic neuritis classified clinically?

• Typical vs. atypical (based on cause/course)

• Retrobulbar vs. papillitis (based on anatomy):

  • Retrobulbar: nerve behind eye → normal disc (“patient sees nothing, doctor sees nothing”)

  • Papillitis: optic disc swelling visible

What is the relationship between typical/atypical optic neuritis and retrobulbar/papillitis?

• Most cases:

  • Typical ON = retrobulbar (associated with demyelinating disease/MS)

  • Atypical ON = papillitis

→ BUT: mild disc swelling can still occur in typical ON

What is the typical epidemiology of MS-related (typical) optic neuritis?

• Age: 15–50 years (average ~32)

• Female predominance (≈3:1)

• More common in Caucasians (~85%)

What demographic + clinical profile should make you think “typical MS optic neuritis”?

• Young adult (20–40s)

• Female

• Unilateral, painful vision loss

• Retrobulbar (often normal disc)

• Improves over weeks

What are the presenting symptoms of typical optic neuritis?

• Acute monocular vision loss (hours → days)

• Periocular pain (often before or at onset)

• Pain worse with eye movement

What additional sensory symptoms can occur in typical optic neuritis?

• Photopsias (flashes of light, “sparks”)

• Uhthoff’s phenomenon: Worsening vision with heat/exertion

What are the key exam findings in typical optic neuritis?

• Decreased visual acuity (mild → severe)

• Relative afferent pupillary defect (RAPD)

• Decreased color vision (especially red desaturation)

• Reduced contrast sensitivity

What visual field defect is most characteristic of typical optic neuritis?

Central scotoma (most common), but other VF defects can occur

Why is the most common visual field defect in typical optic neuritis a central scotoma?

A central scotoma is common due to involvement of papillomacular bundle

What range of visual field defects can occur in typical optic neuritis?

• Central scotoma

• Diffuse vision loss

• Altitudinal defects

• Arcuate defects

• Hemianopic defects

• Cecocentral scotoma

What is a cecocentral scotoma?

Defect between MAC and ONH.

What is the natural history of visual field defects in typical optic neuritis?

• Often improve or resolve over time

• ONTT data:

  • ~56% normalize by 1 year

  • ~73% normalize by 10 years

What are the typical ophthalmoscopic findings in typical optic neuritis?

• Normal fundus (retrobulbar ON) → ~65%

• Optic disc swelling (papillitis) → ~35%

  • Blurred disc margins

  • Filling of cup

• Papillary hemorrhages may occur (~6%)

What fundus findings help distinguish typical optic neuritis from other causes like neuroretinitis?

No macular star in typical ON

What does optic disc pallor indicate in the setting of typical optic neuritis?

Optic nerve head pallor (~10%) indicates previous optic neuropathy / prior damage, not acute phase

What are the OCT findings in eyes with a history of optic neuritis?

Reduced RNFL (retinal nerve fiber layer) thickness, reflecting axonal loss after inflammation

How much RNFL thinning is typically seen after typical optic neuritis?

~27% average reduction in RNFL thickness (affected vs unaffected eye)

What is the clinical significance of OCT in typical optic neuritis and MS?

• Detects structural axonal loss (RNFL thinning)

• RNFL abnormalities can occur even without prior optic neuritis in MS

Useful for:

• Supporting MS diagnosis

• Monitoring disease activity/progression

Can the fellow (asymptomatic) eye show abnormalities in “unilateral” typical optic neuritis?

Yes, subclinical abnormalities are common

What types of abnormalities can be seen in the fellow eye in typical optic neuritis?

• Reduced visual acuity (~14%)

• Decreased contrast sensitivity (~15%)

• Color vision deficits (~21%)

• Visual field defects (~48%)

What is the typical timeline of vision loss in typical optic neuritis?

• Progressive vision loss over ~7–10 days

• Stabilizes by ~2 weeks

What is the typical recovery course in typical optic neuritis?

• ~90% improve over weeks

• Dramatic improvement in 2-8 weeks

What are the typical visual outcomes in optic neuritis?

Good prognosis overall

• 20/40 or better: ~87%

• <20/200: ~8%

What residual deficits can persist after recovery from optic neuritis?

Even with “good” acuity:

• Color vision deficits (↓ red perception)

• Reduced contrast sensitivity / brightness

• Stereo deficits

• RAPD

• Optic disc pallor

• Delayed VEP latency

Why do many patients report persistent visual issues despite “normal” visual acuity after optic neuritis?

• Subtle deficits (color, contrast, brightness) persist

• ~85% of patients with ≥20/30 acuity still perceive imperfect vision

What was the Optic Neuritis Treatment Trial (ONTT) and why is it important?

• Large RCT (~450 patients)

• Compared:

  • IV steroids → oral taper

  • Oral steroids alone

  • Placebo

What key clinical insights did the ONTT provide about optic neuritis?

Defined:

• Natural history (good recovery)

• Typical clinical course

• Visual outcomes

What is the standard steroid regimen for typical optic neuritis based on ONTT?

IV methylprednisolone x3days followed by Oral Prednisone for ~2 weeks. Then taper

How do IV steroids, oral steroids, and placebo compare in optic neuritis (ONTT)?

• IV steroids → faster recovery ONLY (no long-term benefit)

• Placebo → same final visual outcomes as IV

• Oral steroids alone → NO benefit + worse outcomes (↑ recurrence)

Which treatment increases recurrence risk in optic neuritis and by how much?

Oral prednisone alone: 44% vs 30% in placebo and IV steroid groups

What is the risk of developing optic neuritis in the fellow eye?

~17% risk of occurrence in the other eye

How do steroids affect the development of multiple sclerosis in ONTT?

• IV steroids may delay MS onset, especially in patients with MRI lesions

• BUT do not prevent MS long term

What is the initial workup for suspected typical optic neuritis?

MRI of the brain with contrast to evaluate for demyelinating lesions. LP, VEP, and labs are generally not necessary

How should patients with normal MRI be managed in typical optic neuritis?

• Often no treatment required

• Spontaneous recovery common

• Close follow-up over weeks to check for improvement

How should patients with abnormal MRI (white matter lesions) be managed?

• IV methylprednisolone → oral taper

• May reduce short-term risk of developing MS

• Also used for faster visual recovery in severe cases

• Consider beta-interferon treatment for those with white matter lesions

What is the risk of developing MS after optic neuritis (ONTT data)?

• ~50% at 15 years overall

• With MRI lesions: ~72%

• Without lesions: ~25%

What is the role of disease-modifying therapy after optic neuritis?

Consider beta-interferon if white matter lesions on MRI

What is the complete evaluation + management algorithm for typical optic neuritis?

1. Get brain MRI

2. If normal MRI → observe + follow-up

3. If abnormal MRI →

   • IV steroids with oral taper

   • Consider MS therapy (e.g., interferon)

4. Avoid oral steroids alone