Content validity of the NEI VFQ-25 in patients with geographic atrophy

Abstract

Purpose : The National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25) was developed to measure vision-related functioning and quality of life in patients with impaired vision. Content validity of the questionnaire in the context of use in geographic atrophy (GA) has not been previously documented. The purpose of this study was to conduct qualitative research in patients with GA secondary to age-related macular degeneration (AMD) to help establish content validity of the NEI VFQ-25.

Methods : Face-to-face, 1:1 interviews were conducted with 16 GA patients in the US (N=5), UK (N=6) and Germany (N=5) as part of an ethnography study. Patients were included if they had a definitive diagnosis of bilateral GA secondary to AMD and with GA lesion area of ≥ 1 disc diameter in the better seeing eye. Patients with choroidal neovascularization (CNV) or other eye conditions that could confound the diagnosis of GA or the impact of the disease on visual function were excluded. A trained interviewer administered the NEI VFQ-25 and questions from a semi-structured interview guide on relevance, comprehensiveness and clarity of the questionnaire. Interviews were conducted in the local language.

Results : The majority of respondents (N=14/16, 87.5%) indicated that the instructions, questions and response options of the NEI VFQ-25 were clear and understandable. The majority of respondents also indicated that items in the questionnaire were relevant (N=13/16, 81.3%) and that there were not important concepts missing from the questionnaire (N=13/16, 81.3%). Time required to complete the questionnaire was generally acceptable, although three patients stated it was a bit too long. No suggested alterations were made in the US or the UK. In Germany, four patients noted that some questions were repetitive, so the questionnaire and time for administration could be potentially shortened. Also in Germany, one patient suggested adding more questions on emotional impact; one patient suggested an item on seeing traffic light colors; and two patients who did not currently drive noted that driving questions were irrelevant.

Conclusions : Interviews with 16 patients with GA secondary to AMD in the US, UK and Germany indicate that the NEI VFQ-25 is generally considered clear and relevant. Some items were considered repetitive by German respondents. This research helps to establish the content validity of the NEI VFQ-25 in the context of use in GA.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.