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Qualitative and Quantitative Validation of Tools with Rating Scales Aimed at Assessing the Quality of University Service-Learning
Published on: August 29, 2025
Construct validation of the Amblyopia and Strabismus Questionnaire (A&SQ) by factor analysis
Elizabeth S van de Graaf1, Joost Felius, Hanneke van Kempen-du Saar
1Department of Ophthalmology, Erasmus MC, University Medical Center Rotterdam, NL-3000 CA Rotterdam, The Netherlands.
Summary
The Amblyopia and Strabismus Questionnaire (A&SQ) effectively measures quality of life (QoL) in patients with these conditions. Factor analysis confirmed the A&SQ
Area of Science:
- Ophthalmology
- Psychometrics
- Quality of Life Research
Background:
- The Amblyopia and Strabismus Questionnaire (A&SQ) was developed to assess quality of life (QoL) in patients with amblyopia and/or strabismus.
- Factor analysis was utilized to validate the underlying dimensions of the A&SQ.
Purpose of the Study:
- To confirm that the questions in the A&SQ correlate with established dimensions of quality of life (QoL).
- To validate the psychometric properties of the A&SQ using factor analysis.
Main Methods:
- Principal Component Analysis (PCA) and orthogonal Varimax rotation were applied to A&SQ responses from 296 participants (controls, patients, historic cohort).
- Correlations among 26 A&SQ items were analyzed to identify underlying factors.
- Factor loadings were examined to align with five a priori hypothesized dimensions.
Main Results:
- PCA identified six factors explaining 70.5% of the variance in A&SQ responses.
- Four factors aligned with hypothesized A&SQ dimensions (social contact/cosmetic, near distance estimation, diplopia, visual disorientation, fear of better eye loss).
- The identified factors accounted for substantial item variance, confirming the instrument's structure.
Conclusions:
- Factor analysis using PCA and Varimax rotation confirmed the a priori hypothesized dimensions of the A&SQ.
- The A&SQ is a validated instrument for assessing quality of life in amblyopia and strabismus patients.
