What is the treatment for partial hemianopia that can progress to complete and bilateral vision loss?

Treatment for Partial Hemianopia with Risk of Progression to Complete and Bilateral Vision Loss

Compensatory scanning training is the recommended first-line treatment for hemianopia, with consideration of individual patient characteristics. 1

Understanding Hemianopia

Hemianopia is a visual field defect characterized by loss of vision in corresponding halves of the visual field in both eyes. It is commonly associated with:

• Stroke (most common cause)
• Traumatic brain injury
• Brain tumors
• Posterior cerebral artery insufficiency 2

The National Institutes of Health Stroke Scale (NIHSS) categorizes hemianopia as:

• Score 1: Partial hemianopia
• Score 2: Complete hemianopia
• Score 3: Bilateral hemianopia 1

Diagnostic Approach

When evaluating a patient with partial hemianopia:

1. Urgent neuroimaging is essential to identify the underlying cause:

   • MRI with gadolinium is preferred
   • MRA/CTA to rule out aneurysm or vascular causes 3

2. Visual field testing to document the extent of the deficit:

   • Formal perimetry (Humphrey automated visual field analyzer)
   • Web-based screening tools may be used for initial assessment 4

3. Assess for associated neurological deficits using standardized scales like NIHSS 1

Treatment Algorithm

1. Treat the Underlying Cause

• For acute ischemic stroke: Consider IV tPA if within treatment window (up to 4.5 hours from symptom onset)

  • tPA improves outcomes with a number needed to treat of 8.3 for minimal or no disability 1
  • Monitor for symptomatic intracerebral hemorrhage (6% risk with tPA) 1

• For compressive lesions: Urgent neurosurgical intervention may be required 3

• For vascular causes: Control risk factors including hypertension, diabetes, and hyperlipidemia 3

2. Vision Rehabilitation Strategies

After treating the underlying cause, implement the following rehabilitation approaches:

a. Compensatory Training (First-Line)

• Scanning training: Teaches patients to make systematic eye movements to compensate for field loss 1
• Reading strategies: For right hemianopia, focus on seeing the end of longer words; for left hemianopia, marking the left margin of text can assist 1
• Practice with laterally scrolling text to improve reading speed and accuracy 1

b. Substitution Approaches

• Peripheral prism eyeglasses: Can expand the visual field, though evidence for effectiveness is limited 1
• Optical devices: May help with specific visual tasks 1

c. Visual Restitution Therapy

• Aims to restore function in the damaged visual field
• Limited evidence for effectiveness compared to compensatory approaches 1, 5

3. Multidisciplinary Support

• Occupational therapy: Essential for addressing limitations in daily activities

  • Environmental and task modifications
  • Training to use assistive technology
  • Strategies for safe mobility 1

• Referral to specialized services:

  • State services for the visually impaired
  • Veteran's Administration services (if applicable)
  • Orientation and mobility specialists 1

Prognosis and Follow-up

• Spontaneous recovery may occur within the first few months after injury 6
• Regular follow-up is essential to monitor for:
  • Progression of visual field defects
  • Response to rehabilitation strategies
  • Development of complications

Common Pitfalls to Avoid

1. Delayed diagnosis: Hemianopia may be overlooked in patients with other neurological deficits

2. Inadequate rehabilitation: Many patients don't receive proper vision rehabilitation services

3. Overlooking functional impact: Hemianopia significantly affects:

   • Reading ability
   • Safe navigation
   • Driving capability
   • Overall quality of life 6

4. Insufficient training duration: Rehabilitation requires consistent practice over time to be effective 5

5. Focusing only on the visual deficit: Address associated cognitive and physical impairments that may affect rehabilitation outcomes

Early intervention with compensatory scanning training offers the best chance to improve functional outcomes and quality of life for patients with hemianopia at risk of progression.