Translation, cross-cultural adaptation, and psychometric evaluation of the colour blind quality of life scale into Vietnamese

This study successfully translated, culturally adapted, and validated the Colour Blind Quality of Life Scale into Vietnamese, demonstrating that the modified CBQoL-VN is a reliable and valid instrument for assessing quality of life in individuals with congenital colour vision deficiency in Vietnam.

The Gist

Imagine you have a very specific ruler designed to measure how much trouble a person has with a broken compass. The original ruler was made in English for people in Western countries. But now, researchers wanted to use this ruler in Vietnam, where the streets are chaotic, the markets are colorful, and the way people live is quite different.

This paper is the story of how they took that English ruler, rebuilt it piece by piece for Vietnamese people, and checked to make sure it still measures accurately.

Here is the breakdown of their journey:

1. The Problem: A Ruler That Doesn't Fit

The researchers started with a questionnaire called the CBQoL (Colour Blind Quality of Life Scale). Think of this as a "Life Difficulty Meter" for people who can't see colors well (color blindness). It asks questions like, "Is it hard to pick out ripe fruit?" or "Does it make you feel anxious?"

However, just translating the words from English to Vietnamese isn't enough. It's like trying to use a map of London to navigate the streets of Hanoi. The original map might mention "subway stations," but in Vietnam, the real challenge is navigating a sea of motorcycles and chaotic traffic lights. The researchers knew they needed to adapt the tool to fit the local "terrain."

2. The Translation Process: The "Back-and-Forth" Dance

To make sure the new Vietnamese version (called CBQoL-VN) was accurate, they didn't just ask one person to translate it. They used a rigorous "forward-backward" method:

• Step 1: An expert translated the English questions into Vietnamese.
• Step 2: A different expert, who hadn't seen the original, translated that Vietnamese version back into English.
• Step 3: They compared the new English version with the original. If the meaning had drifted, they fixed it.

3. The Expert Panel: The "Taste Testers"

Next, they brought in six experts (eye doctors and vision specialists) to taste-test the new questionnaire. They acted like editors checking a draft.

• The Redundancy Check: The experts noticed that two questions about "feeling anxious" were basically saying the same thing in Vietnamese. They decided to cut the duplicates to avoid boring the participants.
• The Clarity Check: They realized that "groceries" and "fruit" were too similar in the Vietnamese context. They tweaked the questions so one was about general shopping and the other was specifically about checking if flowers, fruits, and food were fresh or spoiled.
• The "Vietnam Special" Addition: This is the most creative part. The original English ruler didn't have a question about traffic. But in Vietnam, where 89% of people ride motorcycles, distinguishing traffic lights is a huge safety issue. The experts added a brand new question specifically about traffic lights and signs to make the ruler truly fit the Vietnamese experience.

4. The Final Product: A 22-Item Tool

After all the editing, the final Vietnamese ruler had 22 questions (down from the original 23, but with one new traffic question added). It covers three main areas:

1. Health & Lifestyle: (e.g., picking clothes, cooking, navigating traffic).
2. Emotions: (e.g., feeling embarrassed or anxious).
3. Work & Study: (e.g., limitations on career choices).

5. The Proof: Does It Work?

The researchers tested this new tool on two groups of people:

• Group A: 30 people with color blindness.
• Group B: 30 people with normal color vision.

The Results:

• Consistency: When the color-blind group answered the questions, their answers were very consistent with each other. It was like a choir singing in perfect harmony. The tool was reliable.
• Discrimination: The tool successfully told the two groups apart. The people with color blindness scored significantly lower (meaning they reported more difficulties) than the people with normal vision. This proved the tool is actually measuring the specific struggles of color blindness, not just general life stress.

The Bottom Line

The researchers successfully built a Vietnamese version of the Color Blind Quality of Life Scale. They didn't just translate words; they remodeled the questions to fit the local culture (like adding the traffic question) and removed confusing parts. The result is a tool that is now ready to help doctors and researchers in Vietnam understand exactly how color blindness affects the daily lives of their patients.

Technical Summary

Technical Summary: Translation, Cross-Cultural Adaptation, and Psychometric Evaluation of the Colour Blind Quality of Life Scale into Vietnamese

Problem Statement
Congenital colour vision deficiency (CVD) affects approximately 8% of men and 0.4% of women globally, imposing significant functional and psychosocial challenges. While diagnostic tools like Ishihara plates effectively identify the presence of CVD, they fail to capture the subjective burden of the condition on an individual's quality of life (QoL). The Colour Blind Quality of Life Scale (CBQoL) was developed to address this gap; however, direct translation of such instruments is often insufficient due to cultural and linguistic differences. Specifically, the Vietnamese context presents unique environmental factors—such as a high-density, mixed-traffic system dominated by motorcycles and a reliance on traditional open markets for food selection—that are not captured by Western-developed instruments. Prior to this study, no validated instrument existed in Vietnam to assess the QoL of individuals with congenital CVD.

Methodology
This study employed a two-phase design to translate, adapt, and validate the CBQoL for the Vietnamese population (CBQoL-VN).

• Phase I (Translation): The process followed World Health Organization (WHO) guidelines, utilizing forward-backward translation. A bilingual subject matter expert translated the original English CBQoL into Vietnamese, followed by a backward translation by a linguistic expert with medical experience. Discrepancies were resolved by a third linguistic expert to produce a pre-final version.
• Phase II (Validation and Reliability):
  • Content Validation: Six experts in eye health (three ophthalmologists, two academic optometrists, and one primary care optometrist) evaluated the draft. They assessed items for relevance, clarity, and understandability using a 4-point Likert scale. The Content Validity Index (CVI) was calculated at both the item (I-CVI) and scale (S-CVI) levels. Based on expert consensus, items were removed, rephrased, or added to ensure cultural equivalence.
  • Reliability Testing: 30 participants with confirmed congenital CVD (mean age 26.70 ± 9.34) completed the modified scale. Internal consistency was measured using Cronbach's Alpha.
  • Discriminant Validity: A control group of 30 individuals with normal colour vision (mean age 23.47 ± 2.30) was recruited. The Mann-Whitney U test was used to compare scores between the CVD and normal vision groups to assess the instrument's ability to distinguish between the two populations.

Key Contributions and Modifications
The study resulted in a modified 22-item instrument (CBQoL-VN), down from the original 23 items, with specific adaptations to the Vietnamese context:

• Item Reduction: Two items in the emotional domain (Original Items 16 and 17) were removed due to semantic overlap and redundancy in the Vietnamese translation.
• Item Refinement: Item 8 was revised to explicitly include "flowers, fruits, and food" to distinguish it from general grocery shopping (Item 2), reflecting local market practices. Items 3, 9, and 22 were rephrased for clarity and contextual relevance (e.g., updating map references to include electronic navigation and ride-hailing services).
• Item Addition: A new transportation-related item was added to the "Health and lifestyle" domain to address the specific safety risks associated with navigating Vietnam's chaotic, motorcycle-heavy traffic, a factor not present in the original scale.
• Structural Changes: The order of items within domains was rearranged to facilitate participant recall.

Results

• Content Validity: The modified CBQoL-VN achieved perfect agreement among experts, with I-CVI and S-CVI values of 1.0 for relevance, clarity, and understandability across all 22 items.
• Reliability: The full scale demonstrated excellent internal consistency with a Cronbach's alpha of 0.95. Subscale reliability was also high: "Health and lifestyle" (0.93), "Emotions" (0.90), and "Work and study" (0.89). All items showed positive corrected item-total correlations.
• Discriminant Validity: Participants with congenital CVD scored significantly lower (indicating greater difficulty and lower QoL) than the normal vision group across all domains and the full scale (p < 0.001).

Significance and Limitations
The authors conclude that the modified CBQoL-VN is a valid and reliable instrument for assessing the quality of life of individuals with congenital CVD in Vietnam. The study emphasizes that the adaptation process successfully moved beyond simple linguistic translation to achieve conceptual and experiential equivalence, particularly by incorporating local transportation and market challenges.

The paper modestly acknowledges specific limitations:

1. Sample Size: The small sample size (n=30) for the CVD group precluded the use of factor analysis to statistically confirm the structural domains, though internal consistency remained high.
2. Recruitment Bias: The inclusion criteria required participants to be currently studying or employed, potentially narrowing the demographic scope.
3. Diagnostic Scope: The reliance on Ishihara plates for diagnosis may have excluded individuals with tritan-type deficiencies, as these plates are designed primarily for protan and deutan defects.

Despite these limitations, the study provides a crucial tool for researchers and clinicians in Vietnam to identify specific QoL burdens, potentially enabling more targeted vocational counseling and support for individuals with colour vision deficiency.