Visual overload after acquired brain damage: What it is and how we can measure it.

The experience of being visually overloaded is frequently reported after acquired brain damage (ABD). Patients suffering from visual overload commonly report to be overwhelmed by the amount and diversity of visual input that others may experience as normal. Despite common observations of visual overload complaints in clinical practice, there is still no clear definition of visual overload and underlying causes are currently unknown. This may be related to the variety of symptoms that patients typically report in clinical practice and the lack of knowledge about visual overload. Given that currently there are no diagnostic tools that can accurately measure visual overload symptoms or their underlying cause, patients face misunderstanding of their difficulties and a lack of sympathy for their situation in various settings. Moreover, the lack of diagnostic tools for visual overload, makes it hard for clinical workers and researchers to develop effective treatments. Supported by a multidisciplinary team of clinicians, researchers, and patient experts, the primary aim of the proposed study is to define visual overload and make the underlying causes measurable. Therefore, we will (1) develop diagnostic tools to measure visual overload symptoms and its potential causes, (2) perform a clinical study to validate the diagnostic tools and to get insights in the prevalence and the underlying causes of visual overload after ABD, and (3) design a directed plan for developing new interventions based on the results of the project. Due to the diversity of symptoms observed in clinical practice, we argue that visual overload complaints can have various underlying causes, each requiring a different diagnostic test. We hypothesize that some overload symptoms can result from damage to the visual system itself (ranging from basic to higher order visual function), which can be measured using clinical tests that are already available. For example, complaints in relation to light sensitivity can be measured in a light lab. However, we hypothesize that complaints such as difficulties with filtering information (e.g. attention) and/or processing both visual and auditory information at the same time can result from impairments in attention or the inability to combine sensory information (e.g. hearing and vision; multisensory integration), respectively. To define visual overload after ABD and identify the underlying causes, we will develop a sensory overload questionnaire, use objective visual tests, and develop tests to measure attention and multisensory integration. The results will give important insights into the definition of visual overload and moreover, it will give information about the prevalence and underlying causes of visual overload complaints. These findings will provide a basis for a better understanding, recognition, and acceptance of visual overload symptoms after ABD and health care providers could develop patient-tailored interventions.