Ocular Surface Disease Index Questionnaire (OSDI-Q), Unidimensionality, and Differential Item Functioning

Objective The OSDI-Q is a 12-item scale used instrument for DED prevalence, assess symptom severity, and impact on vision-related functioning. The research analysis investigates the precision, separation index and reliability of unidimensionality, and DEF, stratified by age and gender. The reliability analysis is to assess the internal consistency of the scale using Cronbach's α coefficient and McDonald's ω coefficient with item-rest correlations. Method 634 respondents took part in the OSDI questionaire. Rasch analysis was conducted using precision, separation index, and reliability for items and person, item and person fit statistics, assessing unidimensionality stratified by age and gender, and the use of SPSS to conduct the reliability analysis of the scale using analytical coefficients. Results The OSDI-Q items displayed robust reliability, with high PSI values of 7.63 and 0.98, respectively. Infit and outfit statistics were within acceptable ranges, explaining 39.90 % of variance. Differential item functioning was observed among the age groups involved. Additionally, the contrast in the principal component analysis of the unexplained variance exhibited an eigenvalue of 2.80 and a proportion of variance of 14%. DIF analysis showed significant differences for age groups of (16-26 years) and (27-40 years). The coefficients of Cronbach's and McDonald's are 0.85 for OSDI-Q demonstrated strong internal consistency. Conclusions OSDI-Q displayed appropriate infit and outfits. DIF analysis results of OSDI-Q of age group (16-26 years) performed better in poor vision while age group (27-40 years) performed better in areas with low humidity. Furthermore, the results of DIF analysis in males group performed better in driving at night, while the female group showed better performance in the questinaire. The OSDI-Q items scale reliability data for Cronbach's scale show high internal consistency and reliability. This research can help the medical communities to begin a better surge for medically integrated research.