Advanced neovascular age related macular degeneration and other retinal exudative diseases, such as diabetic macular edema and cystoid macular edema due to retinal venous occlusion, are the leading causes of legal blindness and low vision in people aged over 50 in developed countries [1, 2]. In contrast to venous occlusion, abovementioned eye diseases often occur in both eyes.
Patients with exudative retinal diseases can experience severe central vision loss within a few days or weeks. Intraocular injections of anti-vascular endothelial growth factor (anti-VEGF) into the eye can be beneficial, i.e. several clinical studies assessing anti-VEGF have shown a significant gain in visual acuity and an increase of vision-related quality of life [3,4,5,6,7,8,9]. However, despite beneficial clinical outcomes, patients may find anti-VEGF injections a burden due to the treatment regimen involving the injections and clinical examinations that are often planned (bi-)monthly in the first period of treatment . The treatment focusses on reducing leakages and stabilization of the growth of new blood vessels. Despite these treatments, the loss of central vision affects the daily activities of many of these patients. The impact of visual impairment on quality of life and the psychological burden of vision loss is well known [11,12,13] .
Clinical measures and performance based measures, such as visual acuity, reading acuity or reading speed and the complications that are directly related to treatment, are routinely registered outcomes in clinical practice . Moreover, Patient Reported Outcome Measures (PROMs), such as quality of life questionnaires, have been developed to evaluate patients’ wellbeing, functioning or disability from their own perspectives, and for this reason are considered meaningful and of direct relevance to patients . Additionally, PROMs are considered a valuable source of information for evaluating health services, establishing treatment effectiveness, informing clinical decision-making and supporting patients in raising their concerns. Moreover, the routine clinical use of PROMs may positively influence doctor-patient communication, shared decision-making and satisfaction with care [12, 14]. The use of PROMs in addition to clinical measures has not gained common ground in ophthalmological practice , however, the PROM to evaluate cataract surgeries is being increasingly used.
A working Group, facilitated by the International Consortium for Health Outcomes Measurement (ICHOM), recommended the use of the Impact of Vision Impairment questionnaire (IVI) for patients with exudative retinal diseases . The IVI is a vision-related quality of life questionnaire (PROM) that contains 28 items and was developed to measure how vision impairment impacts on the ability to participate in daily activities.
To develop the IVI, the Centre of Eye Research Australia, conducted patient focus groups to identify all important activities that could result in a restriction of participation. In addition, existing instruments, such as the Bristol Vision-Related Quality of Life (VQOL), the National Eye Institute-Visual Function Questionnaire (NEI-VFQ), the Activities of Daily Vision Scale and the Visual Function (VF)14 questionnaire, were reviewed for relevant content. The first trial version of the IVI consisted of 76 items, of which 69 overlapped with items in the VQOL. Subsequently, the IVI was first developed as a 32-item version and later into a 28-item version and the Brief-IVI has 15 items. All versions contain the 10 core items of the VQOL [12, 15,16,17,18], which is known as the Vision Related Quality of Life Core Measure (VCM1). The IVI has been found to be reliable and is responsive to interventions such as anti-VEGF treatment.
The IVI has been translated into eight languages. The brief-IVI has been translated into the Dutch language. However, the full IVI, which is considered useful in creating a more comprehensive item bank for future use in a computer adaptive test, has not been translated yet. A sound translation approach should include qualitative pretesting of questionnaires using cognitive interviews, such as the Three-Step Test-Interview (TSTI) [19,20,21], to investigate the comprehensibility, relevance and comprehensiveness of the translated items, as evidence of content validity in a new population [22, 23]. The aim of our study was to translate the original full English-language IVI into Dutch and to evaluate its content validity in patients receiving anti-VEGF.