title: The Computer-Vision Symptom Scale (CVSS17): development and initial validation.
abstract: OBJECTIVE
  To develop a questionnaire (in Spanish) to measure computer-related visual and ocular symptoms (CRVOS).
  
  
  METHODS
  A pilot questionnaire was created by consulting the literature, clinicians, and video display terminal (VDT) workers. The replies of 636 subjects completing the questionnaire were assessed using the Rasch model and conventional statistics to generate a new scale, designated the Computer-Vision Symptom Scale (CVSS17). Validity and reliability were determined by Rasch fit statistics, principal components analysis (PCA), person separation, differential item functioning (DIF), and item-person targeting. To assess construct validity, the CVSS17 was correlated with a Rasch-based visual discomfort scale (VDS) in 163 VDT workers, this group completed the CVSS17 twice in order to assess test-retest reliability (two-way single-measure intraclass correlation coefficient [ICC] and their 95% confidence intervals, and the coefficient of repeatability [COR]).
  
  
  RESULTS
  The CVSS17 contains 17 items exploring 15 different symptoms. These items showed good reliability and internal consistency (mean square infit and outfit 0.88-1.17, eigenvalue for the first residual PCA component 1.37, person separation 2.85, and no DIF). Pearson's correlation with VDS scores was 0.60 (P < 0.001). Intraclass correlation coefficient for test-retest reliability was 0.849 (95% confidence interval [CI], 0.800-0.887), and COR was 8.14.
  
  
  CONCLUSIONS
  The Rasch-based linear-scale CVSS17 emerged as a useful tool to quantify CRVOS in computer workers. : Spanish Abstract.
authors.affiliation: Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Mariano
authors.initials: M
authors.lastname: González-Pérez
authors.affiliation: Faculty of Statistical Studies, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Susi
authors.affiliation: Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Antona
authors.affiliation: Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Barrio
authors.affiliation: Faculty of Optics and Optometry, Universidad Complutense de Madrid, Madrid, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: González
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001248:Asthenopia / Q000175:diagnosis; D016288:Computer Terminals; D004185:Disability Evaluation; D015352:Dry Eye Syndromes / Q000175:diagnosis; D005128:Eye Diseases / Q000175:diagnosis*; D005260:Female; D006304:Health Status; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: VDT; asthenopia; computer; questionnaire; scale