title: Rasch analysis in the development of a simplified version of the National Eye Institute Visual-Function Questionnaire-25 for utility estimation.
abstract: OBJECTIVE
  Preference-based health measures value how people feel about the desirability of a health state. Generic measures may not effectively capture the impact of vision loss from ocular diseases. Disease-targeted measures could address this limitation. This study developed a vision-targeted health state classification system based on the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25).
  
  
  METHODS
  Secondary analysis of NEI VFQ-25 data from studies of patients with central (n = 932)- and peripheral-vision loss (n = 2,451) were used to develop a health state classification system. Classical test theory and Rasch analyses were used to identify a smaller set of NEI VFQ-25 items suitable for the central- and peripheral-vision-loss groups.
  
  
  RESULTS
  Rasch analysis of the NEI VFQ-25 items using the peripheral vision-loss data indicated that 11 items fit a unidimensional model, while 14 NEI VFQ-25 items fit using the central-vision-loss data. Combining peripheral-vision-loss data and central-vision-loss data resulted in 9 items fitting a unidimensional model. Six items covering near vision, distance vision, social vision, role difficulties, vision dependency, and vision-related mental health were selected for the health-state classification.
  
  
  CONCLUSIONS
  The derived health-state classification system covers relevant domains of vision-related functioning and well-being.
authors.affiliation: Global Health Outcomes Strategy and Research, Allergan Inc, 2525 Dupont Drive, Irvine, CA 92612, USA. kowalski_jonathan@allergan.com
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Kowalski
authors.forename: Anne M
authors.initials: AM
authors.lastname: Rentz
authors.forename: John G
authors.initials: JG
authors.lastname: Walt
authors.forename: Andrew
authors.initials: A
authors.lastname: Lloyd
authors.forename: Jeff
authors.initials: J
authors.lastname: Lee
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Young
authors.forename: Wen-Hung
authors.initials: WH
authors.lastname: Chen
authors.forename: Neil M
authors.initials: NM
authors.lastname: Bressler
authors.forename: Paul
authors.initials: P
authors.lastname: Lee
authors.forename: John E
authors.initials: JE
authors.lastname: Brazier
authors.forename: Ron D
authors.initials: RD
authors.lastname: Hays
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Revicki
mesh_terms: D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D054554:National Eye Institute (U.S.); D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D014481:United States; D014786:Vision Disorders / Q000145:classification / Q000175:diagnosis*