Background People with ViD report symptom (i.e. postural and/or gait instability, dizziness, disorientation) provocation or exacerbation in environments with busy or conflicting visual motion including crowds, supermarkets and scrolling computer screens. Visual dependence and impaired sensory re-weighting have been identified as main contributors to balance problems in persons with vestibular disorders and are frequently associated with high disability levels, prolonged illness, and poorer clinical outcome in adults with vestibular dysfunction including vestibular migraine.
Evidence suggests that ViD symptoms respond well to rehabilitation incorporating structured exposure to OKS. Treatment with gradual, progressive exposure to OKS in combination with static and dynamic functional balance exercises has been shown to improve visual dependency, functional balance and gait as well as symptoms provoked or exacerbated in busy visual environments, such as crowds, in persons with a vestibular disorder. It is believed that improvements in ViD following treatment with OKS is due to sensory-reweighting which is the ability of CNS to adapt its relative reliance on a specific sensory modality for purposes of orientation depending on environmental conditions, task demands and/ or pathology.
During neuroimaging studies, exposure to visual OKS, in the absence of vestibular stimulation, results in consistent activation of cortical regions involved in the control of visual motion processing and eye movement, and deactivation of parieto-insular vestibular cortices indicating a reciprocally inhibitory visual-vestibular interaction. Similarly, stimulation of multisensory vestibular cortex areas results in bilateral deactivation in visual and somatosensory cortex areas. These interactions may have a functional significance and indicate a sensor re-weighting process with greater weight given to the more reliable input thus suppressing the possible mismatch between contrasting sensory information. It is believed that the recurring exposure to conflicting visual input promotes reduced visual reliance and facilitates a more effective use of vestibule-proprioceptive cues through sensory re-weighting.
However, the exact mechanisms involved in sensory re-weighting in persons with visual induced dizziness remain poorly understood.
Finally, previous work has demonstrated that low tech OKS provided via a DVD produces the same level of improvement as a more expensive, full field stimulus. Findings for the effect of virtual reality (VR) on ViD are inconclusive. Furthermore, to date only VR provided via an immersive projection theatre, often referred to as a CAVE has been used to investigate its effect on ViD. This equipment is very expensive and available only within a specialist centre. No studies have investigated if 'lower-tech' VR such as VR headset and specifically, Oculus Quest headset, may be beneficial in treatment of ViD at a much lower cost. The use of 'lower-tech' OKS equipment is promising, more widely available to clinical practice and safe to be used at home by the patients for rehabilitation purposes. However, it is not known if one type of 'lower-tech' equipment may provide greater benefit compared to another.
Purpose of the study The proposed pilot study is a non-commercial-PhD student project. The purpose of this investigation is to compare two types of OKS based VRT for the improvement of ViD in persons with a chronic vestibular disorder.
Objectives/Aims of the study The primary objective of this study is to compare the effect of two types of optokinetic stimulation (OKS) based vestibular rehabilitation (VRT) programmes on Situational Characteristics Questionnaire (SCQ) scores in persons with a chronic vestibular disorder who experience ViD aged 18-50 years old.
The secondary objectives are to compare the pre-post treatment effect of two types of OKS based VRT on subjective dizziness, psychological state, balance confidence and objective gait, balance and ViD symptoms.
Primary Hypothesis Both types of OKS will provide significant improvement on SCQ scores, but improvement with VR will be greater.
Secondary Hypothesis VRT with VR Oculus Quest headset may provide greater treatment outcome on gait and balance control, participant's subjective symptoms, psychological state and cognitive function.
