title: Psychometric properties of the NEI-RQL-42 questionnaire in keratoconus.
abstract: OBJECTIVE
  To assess the psychometric properties of the National Eye Institute Refractive Error Quality of Life (NEI-RQL-42) questionnaire in keratoconus and compare these findings to patients with refractive error correction alone.
  
  
  METHODS
  The Portuguese version of the NEI-RQL-42 Quality of Life questionnaire was completed by 44 patients who had keratoconus before and after implantation of intracorneal ring segments. Rasch analysis was used to assess the use of response categories, success in measuring a single trait per subscale (unidimensionality), ability to discriminate person ability (precision), and targeting of questions to person quality of life (QoL).
  
  
  RESULTS
  Rasch analysis was performed for the questionnaire subscales using stacked preoperative and postoperative data. Three subscales (Symptoms, Dependence on correction, and Suboptimal correction) contained response categories that were not used as intended. Six subscales contained misfitting items indicating multidimensionality. Eleven subscales exhibited inadequate measurement precision. Only the Near vision subscale demonstrated adequate precision with a person separation greater than 2.0. Targeting of items to person QoL was adequate in 11 of the 12 subscales with a mean item location of less than 1 logit.
  
  
  CONCLUSIONS
  Only one NEI-RQL-42 subscale (Near vision) performed adequately in keratoconus. Targeting was better in patients with keratoconus than in patients with refractive error correction alone, but 11 of the 12 subscales remain manifestly inadequate. Better instruments exist for measuring patient-reported outcomes in keratoconus.
authors.affiliation: National Health and Medical Research Council Centre for Clinical Eye Research, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, South Australia, Australia. colm.mcalinden@gmail.com
authors.forename: Colm
authors.initials: C
authors.lastname: McAlinden
authors.forename: Jyoti
authors.initials: J
authors.lastname: Khadka
authors.forename: Juliane
authors.initials: J
authors.lastname: de Freitas Santos Paranhos
authors.forename: Paulo
authors.initials: P
authors.lastname: Schor
authors.forename: Konrad
authors.initials: K
authors.lastname: Pesudovs
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000523:psychology*; D008297:Male; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life; D018434:Sickness Impact Profile; D013021:South Australia; D011795:Surveys and Questionnaires; D055815:Young Adult