What is the best way to assess vision impairment in Acquired Brain Injury (ABI) as an Occupational Therapist (OT)?

Comprehensive Assessment of Vision Impairment in ABI by Occupational Therapists

The most effective approach for occupational therapists to assess vision impairment in Acquired Brain Injury (ABI) is through a structured evaluation that includes standardized assessments of visual acuity, contrast sensitivity, central visual field, and functional vision performance in daily activities. 1

Core Assessment Components

1. Visual Acuity Assessment

• Use portable test charts that can be administered at closer distances for patients with significant visual impairments:
  • ETDRS chart at 1 meter
  • Colenbrander Chart
  • Berkeley Rudimentary Vision Test (at 25 cm)
• Document both distance and near visual acuity
• Note any head turns, deviated gaze, or searching eye movements during testing 1

2. Contrast Sensitivity Testing

• Essential for understanding functional vision performance
• Use printed tests (e.g., Pelli-Robson) or computer-based tests
• Include reading tests with varied contrast to demonstrate difficulties with low-contrast text 1

3. Central Visual Field Assessment

• Evaluate for scotomas (non-seeing areas surrounded by seeing areas)
• Assess fixation stability and preferred retinal locus (PRL)
• Document eccentric viewing patterns 1

4. Standardized Visual Perception Screening

• Use comprehensive screening tools such as:
  • Occupational Therapy Adult Perceptual Screening Test (OT-APST) 2
  • Brain Injury Visual Assessment Battery for Adults (biVABA) 3
• These tools assess for:
  • Visual agnosia
  • Visuospatial skills
  • Body scheme awareness
  • Neglect
  • Constructional skills
  • Apraxia
  • Acalculia 2

Functional Vision Assessment

1. Activities of Daily Living Observation

• Assess how vision impairment affects:
  • Self-care activities
  • Medication management
  • Reading performance
  • Visual search and scanning of the environment
  • Safe mobility 1

2. Environmental Factors Evaluation

• Assess patient's response to:
  • Different lighting conditions
  • Contrast levels
  • Patterns in the visual environment
  • Glare sensitivity 4

3. Specialized Assessments for Hemianopia and Neglect

• Evaluate reading limitations caused by field loss
• Assess scanning strategies during functional tasks
• Document awareness of visual deficits 1

Important Considerations

Objective vs. Subjective Assessment

• Combine both objective measurements and subjective reports
• Do not rely solely on patient self-reporting of visual symptoms, as research shows many patients with ABI have visual dysfunctions they may not be aware of 5
• The sensitivity and specificity of symptom questionnaires alone are only moderate 5

Interdisciplinary Collaboration

• Consider joint evaluation with ophthalmology when possible
• Ophthalmology can provide specialized assessments such as:
  • Macular perimetry
  • Scanning laser ophthalmoscope evaluation 6
• OT evaluation should focus on functional limitations and how the patient uses remaining vision 6

Common Pitfalls to Avoid

1. Relying solely on standard visual acuity testing, which may miss significant functional impairments
2. Failing to assess contrast sensitivity, which is crucial for daily function
3. Not documenting eccentric viewing patterns or compensatory strategies
4. Overlooking the need for specialized assessment tools designed for ABI population
5. Assuming patients are aware of all their visual deficits 5

Assessment Algorithm

1. Begin with standardized visual function tests (acuity, contrast, fields)
2. Proceed to comprehensive visual perception screening using validated tools
3. Conduct functional vision assessment during meaningful activities
4. Document environmental factors that improve or worsen performance
5. Integrate findings to develop targeted intervention strategies that address:
   • Environmental modifications
   • Task adaptations
   • Visual skills training
   • Use of optical and non-optical devices 1

By following this comprehensive assessment approach, occupational therapists can effectively identify vision impairments in ABI patients and develop appropriate intervention strategies to improve functional outcomes, safety, and quality of life.