Adaptations and interpretation of Intelligence Tests for Adults with Visual Impairment: A Literature Review and Interviews with Healthcare Professionals

This mixed-method study reveals that no valid, standardized intelligence tests or norm-groups currently exist for adults with visual impairment, leading healthcare professionals to rely on verbal subtests and ad-hoc adaptations while highlighting an urgent need for tailored assessment tools.

The Gist

Imagine you are trying to judge how fast a car can drive. You have a standard speedometer that works perfectly for cars with big, clear windshields. But now, you need to measure the speed of a car that has a cracked windshield, or maybe no windshield at all, and is driving in thick fog.

If you just stick the standard speedometer on that car, the numbers might be wrong. The car isn't necessarily slow; the tool just can't "see" the road properly.

This is exactly the problem researchers Cynthia Lamper and her team investigated in their new paper. They looked at how doctors and psychologists try to measure the intelligence of adults who have visual impairments (people who are blind or have low vision).

Here is a simple breakdown of what they found, using some everyday analogies.

The Problem: The "One-Size-Fits-All" Tool Doesn't Fit

Standard intelligence tests (like the famous WAIS-IV) are like a visual puzzle box. They rely heavily on things you have to see: matching shapes, finding differences in pictures, or spotting patterns on a page.

For a person with perfect vision, this is easy. But for someone who is blind or has low vision, trying to solve a visual puzzle is like asking someone to read a book in a dark room. It's not that they can't read; the light just isn't there.

The researchers asked two questions:

1. What does the scientific literature say? (What are the textbooks telling us?)
2. What are the doctors actually doing? (What are the people in the field doing right now?)

What the Literature Said: The "Missing Manual"

The team looked at studies from the last 10 years. It was a bit like searching for a recipe for "Gluten-Free, Sugar-Free, Dairy-Free Chocolate Cake" and finding only eight recipes, none of which actually worked.

• The Findings: There are no new, perfect intelligence tests designed specifically for blind adults.
• The Workarounds: When doctors do test these adults, they usually just take the "visual puzzle box" and try to open it without the lid. They often skip the visual parts and only ask the verbal questions (the "talking" parts of the test).
• The Result: Because they are skipping half the puzzle, they can't calculate a "Total Intelligence Score" (TIQ). It's like trying to guess the total weight of a suitcase by only weighing the left side. You get a number, but you don't know if it's accurate.

What the Doctors Said: The "DIY Mechanics"

The researchers then interviewed nine healthcare professionals in the Netherlands who work with blind adults. These are the mechanics trying to fix the car in the fog.

Here is what they told the researchers:

1. "We have to improvise."
Since there is no perfect tool, doctors make up their own rules. Some use magnifying glasses; some describe pictures out loud; some give the patient extra time. But because everyone does it differently, it's hard to compare one person's results to another's. It's like if every mechanic used a different set of wrenches to fix the same engine.

2. "We are worried about the score."
The doctors admitted that when they skip the visual parts and only test the verbal parts, the final score might be misleading.

• The Risk: A person might be very smart but struggle with the test because they can't see the instructions. The test might say they have a "low" intelligence, when in reality, they just have a "low" vision score on a visual test.
• The Ceiling Effect: Sometimes, blind adults are so good at listening and remembering that they get the "perfect" score on the verbal parts, making it look like they are geniuses, even if we don't know how they handle other types of thinking.

3. "We need a new map."
The doctors are desperate for a standardized protocol. They want a manual that says: "If a patient has this level of vision, do these specific steps, and here is how you interpret the score." Right now, they are driving without a map, hoping they don't get lost.

The Big Takeaway: The "Missing Piece"

The main conclusion of the paper is simple but urgent: We cannot accurately measure the total intelligence of a blind adult right now.

It's not that blind people aren't intelligent. It's that our measuring tape is broken for them.

• Current Practice: Doctors are doing their best with verbal tests and careful observations, but they have to be very careful when writing their reports, adding big warnings like, "This score is an estimate because we couldn't test the visual parts."
• The Future: We need to invent a new "puzzle box" that doesn't rely on sight. We need tests that use touch (haptics) or sound, and we need a new set of "average" scores (norms) specifically for blind people to compare against.

Why Does This Matter?

Imagine you are applying for a job or need support for daily life. If the test says you have a "low" intelligence because the test was too visual, you might be denied the help you actually need. Or, if the test overestimates your skills, you might be put in a situation you can't handle.

The researchers are calling for a new era of testing where the tool matches the person. Until then, doctors must be honest, transparent, and careful, explaining clearly that the "score" is just a snapshot, not the whole picture.

In short: We are trying to weigh a fish using a ruler. It's time to build a scale that actually works for the fish.

Technical Summary

1. Problem Statement

Administering and interpreting intelligence tests for adults with Visual Impairment (VI) presents significant methodological and practical challenges. Standard intelligence test batteries (e.g., WAIS-IV) rely heavily on visual tasks and lack specific normative data (norm-groups) tailored to the VI population.

• The Gap: There is currently no standardized, validated intelligence test for adults with VI that allows for the accurate calculation of a Total Intelligence Quotient (TIQ).
• Consequence: Without tailored tools, healthcare professionals (HCPs) struggle to accurately assess cognitive functioning, which is essential for diagnosis, treatment planning, and determining support needs for daily living and employment.
• Context: While previous reviews exist, they often focus on children or outdated instruments. This study addresses the critical lack of current evidence regarding adult-specific adaptations and interpretation strategies.

2. Methodology

The study employed a mixed-methods design, integrating an exploratory literature review with qualitative interviews to triangulate findings between international research and Dutch clinical practice.

A. Literature Review

• Search Strategy: Conducted across PubMed, PsycINFO, Google Scholar, and Web of Science (Nov 2014 – Nov 2024).
• Inclusion Criteria: Studies addressing adaptations or interpretation of intelligence tests (defined as assessments calculating a TIQ) in adults with VI. Excluded studies focusing solely on children or dual sensory loss.
• Selection: From 3,006 initial records, 8 publications met inclusion criteria (1 review, 2 case-control, 2 cross-sectional, 2 cohort, 1 case report).
• Quality Assessment: Utilized Joanna Briggs Institute (JBI) critical appraisal tools. Quality scores ranged from 27% to 100% (Low to Good).

B. Qualitative Interviews

• Participants: 9 Healthcare Professionals (HCPs) from three Dutch Low Vision Service (LVS) organizations.
• Profile: Mix of psychologists and pedagogical scientists with an average of 16 years of experience in IQ testing and 13 years specifically with VI clients.
• Procedure: Semi-structured interviews conducted via secure platforms, transcribed verbatim, and analyzed using reflexive thematic analysis (double-coded by two researchers).
• Focus: Current practices, challenges in administration, test selection, interpretation of results, and needs for future development.

3. Key Contributions

• Methodological Triangulation: Successfully combined sparse international literature with rich, in-depth clinical insights from Dutch practitioners to provide a comprehensive view of the current landscape.
• Identification of the "TIQ Gap": Confirmed that despite various adaptations, no valid method exists to calculate a Total Intelligence Quotient (TIQ) for adults with VI in the current decade.
• Clinical Guidelines for Practice: Provided a framework for how HCPs currently navigate these limitations, emphasizing the shift toward verbal-only assessments and the critical importance of descriptive reporting over standardized scoring.
• Expert Validation: Validated the need for specific norm-groups and standardized protocols, moving beyond anecdotal adaptations to evidence-based requirements.

4. Key Results

A. Literature Findings

• Test Usage: The WAIS-IV (Wechsler Adult Intelligence Scale – Fourth Edition) is the most frequently used instrument.
• Adaptations: Six of the eight studies reported adaptations, including:
  • Administering only verbal subtests (e.g., Digit Span, Similarities).
  • Using enlarged materials, modified lighting, or auditory versions of tasks.
  • Utilizing tactile alternatives (e.g., Haptic Intelligence Scale for the Blind), though these are rarely implemented in practice.
• Interpretation: Only one study addressed the interpretation of scores for VI adults. None of the studies reported using adapted norm-groups.
• Quality: Methodological quality varied significantly; reviews and cohort studies generally scored lower than case-control and cross-sectional designs.

B. Interview Findings (Themes)

1. Administration Differences: HCPs noted that non-verbal components are often infeasible. They frequently rely on verbal subtests, extend time limits, and use verbal descriptions to replace visual cues. However, this creates fatigue and alters the nature of the test.
2. Test Selection: The WAIS-IV is the default. Specialized tests (e.g., ITVIK) are rarely used for adults due to child-specific norms. HCPs often supplement with adaptive behavior scales (e.g., ADAPT) to get a holistic view.
3. Administration & Norms: No standardized protocols exist within organizations. HCPs express skepticism about the feasibility of creating a single norm-group due to the heterogeneity of VI (congenital vs. acquired, severity levels).
4. Interpretation & Validity:
   • TIQ is Unattainable: Most HCPs agree a TIQ cannot be calculated when only verbal subtests are used.
   • Risk of Bias: There is a risk of underestimating abilities (if non-verbal strengths are missed) or overestimating them (if verbal scores are inflated in blind individuals).
   • Reporting: Reports must explicitly detail adaptations, environmental conditions, and the impact of VI on validity.
5. Needs & Wishes: HCPs urgently desire:
   • Tailored norm-groups for adults with VI.
   • Standardized protocols for administration and interpretation.
   • New tests that measure processing speed and non-verbal reasoning without visual dependence.

5. Significance and Implications

• Clinical Practice: The study concludes that accurate TIQ measurement is currently impossible for adults with VI. Practitioners must rely on predominantly verbal subtests, carefully observe performance, and provide explicit, descriptive reports that contextualize results rather than relying on standard scores.
• Research & Development: There is an urgent need to develop:
  • Specific intelligence tests for adults with VI.
  • Dedicated norm-groups for this population.
  • Standardized manuals outlining adaptation procedures.
• Policy: The findings highlight a critical gap in psychodiagnostics that affects the ability to provide appropriate support, education, and employment accommodations for the growing VI population.
• Future Directions: Research should focus on developing non-visual assessments for processing speed and working memory, and exploring "practical intelligence" (daily functioning) as a complementary metric to traditional IQ.

Conclusion: The paper serves as a definitive call to action for the psychometric community to move beyond ad-hoc adaptations and develop rigorous, validated tools specifically designed for adults with visual impairments to ensure fair and accurate cognitive assessment.