What is nystagmus and how is it managed?

Nystagmus: Diagnosis and Management

Nystagmus is defined as rhythmic, involuntary eye movements that typically consist of a slow pathological drift followed by a fast compensatory refixation saccade, requiring comprehensive evaluation and targeted management based on the underlying cause to improve visual function and quality of life. 1

Types of Nystagmus

Classification by Onset

• Infantile nystagmus (onset in first 6 months of life)

  • Typically caused by albinism, retinal disease, low vision, and congenital cataracts 2
  • May be idiopathic or associated with FRMD7 gene mutations 3
  • Often horizontal, conjugate, and may dampen with convergence

• Acquired nystagmus (later onset)

  • May be caused by anterior optic pathway lesions, brainstem/cerebellar lesions, or metabolic diseases 2
  • Requires urgent neurological evaluation, especially if sudden onset

Classification by Presentation

• Spontaneous nystagmus - occurs in primary position (e.g., upbeat or downbeat nystagmus) 1

• Induced nystagmus - triggered by specific factors:

  • Gaze-evoked nystagmus
  • Head-shaking nystagmus
  • Positional nystagmus (e.g., BPPV-related)
  • Hyperventilation-induced nystagmus 1

• Manifest nystagmus - present constantly; may be horizontal, vertical, and/or torsional 4

• Latent nystagmus - appears only when one eye is occluded; reverses direction with change in fixation 4

• Manifest-latent nystagmus - present under binocular viewing but increases with monocular occlusion 4

Clinical Presentation and Symptoms

• Cardinal symptoms include:

  • Blurred vision
  • Jumping images (oscillopsia)
  • Reduced visual acuity
  • Sometimes double vision
  • Dizziness and postural imbalance (especially with downbeat/upbeat nystagmus)
  • Spinning vertigo with acute onset 1

• Children with nystagmus often present with:

  • Abnormal head postures (to find null point where nystagmus is minimized)
  • Reduced visual acuity
  • Strabismus (especially with latent nystagmus) 3, 5

Diagnostic Approach

1. Detailed ocular examination:

   • Assessment of visual acuity (both monocular and binocular)
   • Measurement of binocular near acuity at 40 cm and at preferred reading distance
   • Use of linear or crowded optotypes for visual acuity testing 2
   • Note: Monocular occlusion can increase nystagmus amplitude 2

2. Nystagmus characterization:

   • Direction (horizontal, vertical, torsional)
   • Amplitude and frequency
   • Effect of gaze position, convergence, and fixation
   • Waveform characteristics 1

3. Neurological red flags requiring urgent evaluation:

   • Asymmetrical or unilateral nystagmus
   • Vertical or torsional nystagmus
   • New onset nystagmus
   • Associated neurological symptoms
   • Progressive nystagmus 2, 3

4. Imaging:

   • MRI of the head without and with IV contrast is recommended for:
     • Late onset nystagmus
     • Concurrent neurological symptoms
     • Decreased visual acuity
     • Asymmetric/unilateral or progressive nystagmus 2
   • CT scans are inadequate and may lead to missed diagnoses 2

5. Additional testing:

   • Electrophysiology (ERG, VEP)
   • Hand-held spectral domain optical coherence tomography (HH SD-OCT) to assess foveal structure 5
   • Genetic testing (especially for FRMD7 gene in hereditary X-linked nystagmus) 5

Management Approaches

Optical Management

• Refractive correction:
  • Even minor refractive errors should be corrected
  • Contact lenses often offer advantages over glasses 3
• Prisms - may help in some cases to shift images to null point

Pharmacological Treatment

• For downbeat and upbeat nystagmus:
  • 4-aminopyridine 1, 6
• For infantile nystagmus, nystagmus in albinism, and sensory nystagmus:
  • Gabapentin
  • Memantine
  • Possibly carbonic anhydrase inhibitors 3, 5, 7
• For periodic alternating nystagmus:
  • Baclofen 1, 6
• For pendular fixation nystagmus:
  • Memantine or gabapentin 1, 6

Surgical Interventions

• For abnormal head posture:
  • Anderson procedure
  • Kestenbaum procedure 3
• For nystagmus that dampens with convergence:
  • "Artificial divergence" procedure of Cüppers 3
• Four-muscle-tenotomy:
  • Disinsertion and reinsertion of horizontal muscles at original insertion
  • Has proven but limited positive effect on visual acuity 3

Rehabilitative Management

• Low-vision rehabilitation is essential for children with visual impairment from nystagmus 2
• Referral to pediatric ophthalmologist for specialized care 2

Special Considerations

• Nystagmus in children requires careful evaluation to distinguish between benign forms and those indicating serious neurological disease
• A retrospective review found 15.5% of children who underwent MRI for isolated nystagmus had abnormal intracranial findings 2
• Children with nystagmus should be preferably managed by a pediatric ophthalmologist, particularly those with early-onset nystagmus or accompanying visual symptoms 2
• Documentation of preferred head posture is critical for surgical planning in patients with strabismus and/or nystagmus 4

Pitfalls to Avoid

• Failing to differentiate between infantile and acquired nystagmus
• Missing underlying neurological causes by inadequate imaging
• Overlooking associated conditions like albinism, retinal disease, or optic nerve abnormalities
• Not recognizing nystagmus blockage syndrome in children with infantile esotropia who use excessive convergence to dampen nystagmus 4