Background: Patient-reported outcomes, such as visual function and quality of life, are met with increasing interest in the assessment of medical interventions. To offer a greater availability of valid psychometric tools in Germany, the German versions of the Impact of Vision Impairment Profile (IVI) and the Low Luminance Questionnaire (LLQ) were evaluated in a sample of patients with geographic atrophy (GA) due to advanced age-related macular degeneration (AMD).

Methods: All questionnaires were translated, back translated and culturally adapted using feedback from patients. Subsequently, the 28-item IVI and 32-item LLQ were administered to 104 patients with GA due to AMD by telephone. Diagnosis had been confirmed within the FAM-study, which is a multi-centre natural history study of GA in Germany. All interviews were conducted by the same trained interviewer. The National Eye Institute Visual Functioning Questionnaire-25 (NEI-VFQ-25) was also administered in order to determine convergent validity of the IVI and LLQ. The study adhered to the tenets of the Declaration of Helsinki and ethical approval had been obtained prior to the commencement of the study.

Results: Mean ±SD age of patients was 78±6.7 yrs (40M, 64F), mean ±SD visual acuity of the better eye was LogMAR 0.4±0.29. Reliability was good for the overall score and subscales of the IVI (Cronbach’s alpha 0.82-0.83) and LLQ (Cronbach’s alpha 0.82-0.91), with a modest Cronbach’s alpha for the peripheral vision scale (0.42). Item-scale correlations ranged from 0.38-0.83 for the IVI and 0.48-0.93 for the LLQ. All scales of the IVI had fair to good correlations with matching subscales of the NEI-VFQ 25 (e.g. IVI scale emotional wellbeing to VFQ scale mental health; 0.48</=r</=0.93; p</=0.01). Similarly, all scales of the LLQ correlated to matching scales of the NEI-VFQ 25 ( 0.30</=r</=0.81; p</=0.04), showing good convergent validity for both questionnaires.

Conclusion: The psychometric evaluation of the German versions of the IVI and the LLQ showed good reliability and validity parameters in a sample of GA patients. Further validation of the two scales using Rasch analysis is currently being undertaken. Against the background of possible future interventions for GA in AMD, both questionnaires appear to be appropriate to assess the effectiveness of new therapies such as visual cycle modulators.