Psychometric Validation of a Short-Form Spanish Low Vision Quality of Life Questionnaire (SF-SLVQOL) Using Rasch...

The Spanish Low Vision Quality of Life Questionnaire (SLVQOL) assesses vision-related quality of life effectively but requires significant administration time. This study aimed to develop and validate a psychometrically robust short-form version (SF-SLVQOL) using Rasch analysis to reduce respondent burden while maintaining measurement precision in Spanish-speaking populations with visual impairment.

Data from the original SLVQOL validation study (n = 365; 170 visually impaired, 195 controls) were reanalysed using Partial Credit Model analysis in WINSTEPS. Items were systematically reduced through iterative removal based on point-biserial correlations (< 0.4) and misfit statistics (infit/outfit outside 0.7-1.3). The resulting SF-SLVQOL was evaluated for structural validity (unidimensionality, local independence, monotonicity), internal consistency (Cronbach's alpha), criterion validity (correlation with original SLVQOL), construct validity (convergent validity with NEI VFQ-25, known-groups validity across ICD-11 visual impairment categories), differential item functioning by gender and test-retest reliability.

The 6-item SF-SLVQOL demonstrated excellent unidimensionality (essential unidimensionality = 93.6%, variance explained = 79.3%), optimal internal consistency (α = 1.00) and high criterion validity (r = 0.95 with original SLVQOL). Convergent validity with the NEI VFQ-25 was confirmed (r = 0.69). The known-groups analysis showed significant discrimination between visual impairment levels (H = 132.67, p < 0.001). Person reliability (0.91) indicated the ability to distinguish 4.3 performance levels. Test-retest reliability was acceptable (ICC = 0.753; 95% CI: 0.569-0.864) with a repeatability limit of 4.89 points.

The SF-SLVQOL successfully reduces administration time by 76% while maintaining robust psychometric properties, offering clinicians and researchers an efficient tool for assessing vision-related quality of life in Spanish-speaking populations.