Measuring the quality of life of visually impaired children: First stage psychometric evaluation of the novel VQoL - CYP instrument

Abstract

Purpose To report piloting and initial validation of the VQoL-CYP, a novel age-appropriate visionrelated quality of life (VQoL) instrument for self-reporting by children with visual impairment (VI). Methods Participants were a random patient sample of children with VI aged 10-15 years. 69 patients, drawn from patient databases at Great Ormond Street Hospital and Moorfields Eye Hospital, United Kingdom, participated in piloting of the draft 47-item VQoL instrument, which enabled preliminary item reduction. Subsequent administration of the instrument, alongside functional vision (FV) and generic health-related quality of life (HRQoL) selfreport measures, to 101 children with VI comprising a nationally representative sample enabled further item reduction and evaluation of psychometric properties using Rasch analysis. Construct validity was assessed through Pearson correlation coefficients. Results Item reduction through piloting (8 items removed for skewness and individual item response pattern) and validation (1 item removed for skewness and 3 for misfit in Rasch) produced a 35-item scale, with fit values within acceptable limits, no notable differential item functioning, good measurement precision, ordered response categories and acceptable targeting in Rasch. The VQoL-CYP showed good construct validity, correlating strongly with HRQoL scores, moderately with FV scores but not with acuity. Conclusions Robust child-appropriate self-report VQoL measures for children with VI are necessary for understanding the broader impacts of living with a visual disability, distinguishing these from limited functioning per se. Future planned use in larger patient samples will allow further psychometric development of the VQoL-CYP as an adjunct to objective outcomes assessment.