title: Measurements of vision function and quality of life in patients with cataracts in southern India. Report of instrument development.
abstract: OBJECTIVE
  To develop and validate vision function (VF) and quality of life (QOL) instruments in patients with cataracts in the context of large volume surgery in a developing country.
  
  
  METHODS
  The instruments were developed using a consensus approach. One hundred patients who were undergoing cataract surgery at Aravind Eye Hospital, Madurai, India, were interviewed preoperatively and 3 and 12 months postoperatively. Standard clinical procedures were followed, including measurement of visual acuity. Between-interviewer reproducibility was measured by repeated administration of the preoperative questionnaire. Within-interviewer reproducibility was measured preoperatively in a separate study of 50 patients.
  
  
  RESULTS
  Preoperative scores from the VF and QOL instruments were significantly associated with visual acuity (r = 0.4). Internal reliability (Cronbach alpha) was greater than .9. Both instruments showed large changes after surgery, with effect sizes of 3 or greater for most VF scales (range, 1.8-3.7) and 1 or greater for QOL scales (range, 1.0-2.2). Changes in visual acuity after surgery were correlated with changes in the VF (r = 0.44) and QOL (r = 0.41) scale scores. Between-interviewer reproducibility was acceptable (total VF scale, Spearman r = 0.7; total QOL scale; r = 0.74). The kappa values were lower for within-interviewer reproducibility.
  
  
  CONCLUSIONS
  The study provided strong evidence for the validity, reproducibility, and responsiveness of the instruments, and for the feasibility of using them in the setting of a large volume of cataract surgery in a developing country.
authors.affiliation: Department of Epidemiology and Population Sciences, London School of Hygiene and Tropical Medicine, England. afletche@lshtm.ac.uk
authors.forename: A E
authors.initials: AE
authors.lastname: Fletcher
authors.forename: L B
authors.initials: LB
authors.lastname: Ellwein
authors.forename: S
authors.initials: S
authors.lastname: Selvaraj
authors.forename: V
authors.initials: V
authors.lastname: Vijaykumar
authors.forename: R
authors.initials: R
authors.lastname: Rahmathullah
authors.forename: R D
authors.initials: RD
authors.lastname: Thulasiraj
mesh_terms: D002386:Cataract / Q000503:physiopathology*; D002387:Cataract Extraction; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011184:Postoperative Period; D011788:Quality of Life; D015203:Reproducibility of Results; D014785:Vision, Ocular; D014792:Visual Acuity