title: Assessment of the impact of keratoconus on vision-related quality of life.
abstract: OBJECTIVE
  We determined if the Impact of Vision Impairment (IVI) is a valid questionnaire to measure the vision-related quality of life (VRQoL) in keratoconus patients, and investigated if the VRQoL varied with disease severity in this sample.
  
  
  METHODS
  WE RECRUITED 160 CONSECUTIVE BILATERAL KERATOCONUS PATIENTS (MEAN AGE 23.3 YEARS, 63% MALE) FROM AN INDIAN TERTIARY EYE CARE CENTER. PARTICIPANTS UNDERWENT A CLINICAL EXAMINATION AND COMPLETED THE IVI. PARTICIPANTS WERE DIVIDED INTO THREE GROUPS BASED ON THE AVERAGE OF THE STEEP KERATOMETRY (K) READINGS: mild (average Sim K < 45 diopters [D]), moderate (average Sim K 45-52 D), and severe (average Sim K > 52 D). Rasch analysis was used to validate the IVI and the VRQoL scores thus obtained were compared across the disease groups.
  
  
  RESULTS
  THE MAJORITY (63%) OF PATIENTS HAD SEVERE, WHILE THE REMAINDER (37%) HAD MODERATE KERATOCONUS. RASCH ANALYSIS DEMONSTRATED THE VALIDITY OF THE IVI TO ASSESS VRQOL THROUGH TWO SUBSCALES: vision-specific functioning (VF) and emotional well-being (EWB). There was no significant difference in VF (mean change -0.16, P = 0.55) and EWB scores (mean change -0.32, P = 0.23) between moderate and severe keratoconus groups.
  
  
  CONCLUSIONS
  The revised IVI subscales have interval-level measurement properties, which support their suitability to measure VRQoL in this keratoconus sample. Patients with moderate or severe keratoconus had similar, but higher VRQoL scores as assessed by the revised IVI subscales, indicating lack of impact of the disease on their VRQoL. However, this does not exclude the possibility of finding an impact in other populations.
authors.affiliation: Meera and L B Deshpande Centre for Sight Enhancement, Vision Rehabilitation Centres, L V Prasad Eye Institute, Hyderabad, India. vijayagothwal@gmail.com
authors.forename: Vijaya K
authors.initials: VK
authors.lastname: Gothwal
authors.forename: Shailaja P
authors.initials: SP
authors.lastname: Reddy
authors.forename: Asma
authors.initials: A
authors.lastname: Fathima
authors.forename: Seelam
authors.initials: S
authors.lastname: Bharani
authors.forename: Rebecca
authors.initials: R
authors.lastname: Sumalini
authors.forename: Deepak K
authors.initials: DK
authors.lastname: Bagga
authors.forename: Preeji M
authors.initials: PM
authors.lastname: Sudharman
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000150:complications / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D011594:Psychometrics / Q000379:methods / Q000592:standards*; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*; D014786:Vision Disorders / Q000209:etiology / Q000523:psychology*; D055815:Young Adult