Re-evaluating a vision-related quality of life questionnaire with item response theory (IRT) and differential item functioning (DIF) analyses

Table 1 Patient characteristics (N = 296)

Gender
Female	183	61.8%
Male	113	38.2%
Age
< 75 years	76	25.7%
≥75 years	220	74.3%
LogMAR visual acuity*
< 0.52 mild vision loss	97	32.9%
≥ 0.52 low vision/blindness	198	67.1%
Main cause of vision loss in best eye*
Age-related macular degeneration	154	52.6%
Other eye conditions	139	47.4%
Rehabilitation type
Optometric service	161	54.4%
Multidisciplinary service	135	45.6%
Administration type*
Self-report	108	37.1%
Assisted	183	62.9%

ISSN: 1471-2288