Qualitative exploration of the visual function impairments and impacts on vision-dependent activities of daily living in Retinitis Pigmentosa and Leber Congenital Amaurosis: content validation of the ViSIO-PRO and ViSIO-ObsRO measures

BACKGROUND: Retinitis Pigmentosa (RP) and Leber Congenital Amaurosis (LCA) are rare inherited retinal degenerative disorders. The associated visual impairments have significant impacts on patients’ vision-dependent activities of daily living (ADL), mobility, and distal health-related quality of life (HRQoL). To adequately capture patient and caregiver perspectives in clinical trials, patient and observer-reported outcome instruments must demonstrate sufficient evidence of content validity in the target population. This study aimed to explore the patient experience of RP/LCA and assess the content validity of the Visual Symptom and Impact Outcomes PRO (ViSIO-PRO) and ObsRO (ViSIO-ObsRO) instruments in RP/LCA. METHODS: A total of 66 qualitative, combined concept elicitation (CE) and cognitive debriefing (CD) interviews were conducted (33 adults, 10 adolescents, 8 children and 15 caregivers of children) in the US, France, Germany, and Canada. Patients had a clinical and genetic diagnosis of RP/LCA from a range of genotypes. CE results were used to further inform the development of a conceptual model and CD interviews assessed the relevance and understanding of the 44-item ViSIO-PRO and 26-item ViSIO-ObsRO instruments. Interviews were conducted across two iterative rounds to allow item modifications. RESULTS: Findings were consistent across RP/LCA genotypes. Night blindness, reduced peripheral vision, vision in very bright lighting and light/dark adaptation were the most frequently reported visual function symptoms impacting vision-dependent ADL and mobility. Impacts on distal HRQoL domains were also reported. The ViSIO-PRO and ObsRO items were well understood by participants and relevant across genotypes. The instructions, 7-day recall period and response scales were well understood and endorsed. Participant and expert clinician feedback supported modifications to item wording, the addition of six new ViSIO-PRO items and one new ViSIO-ObsRO item, and the removal of one ViSIO-PRO item due to lack of relevance. CONCLUSIONS: Findings support the content validity of the ViSIO-PRO and ViSIO-ObsRO instruments for use across RP/LCA genotypes. Ongoing research to evaluate the psychometric validity of the instruments will support future use of the instruments as efficacy endpoints in clinical trials and in general clinical practice to track disease severity and impact of disease on functioning.