What are the visual field deficits in optic neuritis?

Visual Field Defects in Optic Neuritis

The most common visual field defect in optic neuritis is central scotoma, though a wide variety of visual field defects can occur including diffuse loss, nerve fiber bundle defects (arcuate, partial arcuate, paracentral), and altitudinal defects.

Primary Visual Field Defect Patterns

Common Patterns

• Central/Centrocecal Scotoma: Present in approximately 8-68% of optic neuritis cases 1, 2

  • Characterized by a scotoma centered on the fixation point with a sloping border
  • Highly characteristic of optic neuritis compared to other optic neuropathies 3

• Diffuse Visual Field Loss:

  • Present in 48-66% of affected eyes during acute phase 1, 2
  • Represents generalized depression of visual sensitivity across the field
  • More common in the acute phase than in later stages

• Nerve Fiber Bundle Defects:

  • Partial arcuate, paracentral, and complete arcuate defects
  • Become the predominant pattern during recovery and long-term follow-up 2
  • Present in approximately 35-40% of cases after the acute phase

• Altitudinal or Other Nerve Fiber Bundle Defects:

  • Present in approximately 20% of cases 1
  • Superior altitudinal defects seen in about 13% of optic neuritis cases 3
  • Inferior altitudinal defects seen in about 8% of optic neuritis cases 3

Evolution of Visual Field Defects

1. Acute Phase (at onset):

   • Predominantly diffuse visual field loss (66.2% of abnormalities) 2
   • Central scotoma often prominent

2. Recovery Phase (1-15 years):

   • Shift from diffuse to localized defects
   • Nerve fiber bundle defects become predominant (35-40% of abnormalities) 2
   • Foveal threshold highly correlates with visual acuity and contrast sensitivity

Diagnostic Considerations

Differentiating Features from Other Optic Neuropathies

• Optic Neuritis vs. Anterior Ischemic Optic Neuropathy (AION):
  • Central scotoma with sloping border is highly characteristic of optic neuritis (50% of cases) 3
  • Inferior altitudinal defect with sharp border along horizontal meridian is characteristic of AION 3
  • Visual field pattern alone has limited utility in distinguishing between conditions 1

Special Considerations in Different Etiologies

• Multiple Sclerosis-Associated Optic Neuritis:

  • Central scotoma is present in 90% of MS-associated optic neuritis cases 4
  • Visual field examination may show central or arcuate defects 5, 6

• Neuromyelitis Optica (NMO)-Associated Optic Neuritis:

  • Higher incidence of non-central scotoma patterns (47% of cases) 4
  • Altitudinal hemianopia is the most frequent non-central scotoma pattern
  • 13% of NMO patients may never experience central scotoma 4
  • May suggest an ischemic mechanism mediated by anti-aquaporin-4 antibody

Clinical Evaluation

• Visual Field Testing:

  • Full-field testing is essential as restricted perimetry (30 degrees) may miss diagnostic patterns 3
  • Goldmann perimetry or standard automated perimetry can be used
  • Visual-evoked potentials can detect bilateral optic nerve damage before clinically apparent 5, 6

• Fellow Eye Involvement:

  • Asymptomatic visual field defects in the fellow eye are common (68.8% of patients) 1
  • Evidence of chiasmal or retrochiasmal visual field defects present in 2.9% of patients 1

Prognostic Implications

• Visual Recovery:
  • Recovery of high-contrast visual acuity is common in idiopathic and MS-associated optic neuritis 7
  • Residual deficits in contrast sensitivity, binocular vision, and motion perception may persist
  • Recovery may be poorer in patients seropositive for antibodies to myelin oligodendrocyte glycoprotein, AQP4, and CRMP5 7

Treatment Considerations

• Acute Management:

  • High-dose intravenous methylprednisolone is recommended for optic neuritis 5, 6
  • Early treatment is essential, particularly in cases with severe visual field defects
  • Plasmapheresis may be considered in severe cases 5

• Long-term Management:

  • Maintenance immunosuppressive therapy may be needed to prevent relapses 5
  • Anticoagulation may be considered in antiphospholipid-positive patients not responding to immunosuppressive therapy 5

Understanding the pattern of visual field defects in optic neuritis is crucial for accurate diagnosis, determining etiology, and guiding appropriate treatment to preserve visual function.