Age-Related Vestibular Dysfunction; Vestibulo-Ocular Reflex, Dynamic Visual Acuity, Dizziness and Falls: A Review

Background: Vestibular and vision functions are important contributors to posture control and fall avoidance. This review examines how the vestibulo-ocular reflex can be rehabilitated to help restore postural control. Methods: PubMed searches (7th April 2021) using the terms ‘vestibulo-ocular reflex’, ‘imbalance and vestibular dysfunction’, ‘vestibular dysfunction and dizziness’, ‘dynamic visual acuity’, ‘vestibular dysfunction rehabilitation’, and ‘gaze stabilization exercises’ yielded 4986, 495, 3576,1830, 3312, and 137 potentially useful publications respectively. Selections of those which were found to be the most relevant and representative of a balanced and current account of these topics, as well as selections from the most relevant reports referenced in those publications, were included in this review. Results: Just as there are age-related losses of static visual acuity even when there are no specific visual pathologies diagnosed, patients may also present with age-related loss of vestibular functions in the absence of specific vestibular pathologies. For example, cases of dizziness which are diagnosed as idiopathic might be usefully classified as age-related as the basis for the initiation of rehabilitation exercises. Conclusions: Apart from age-related loss of vestibular functions, cases diagnosed as having a particular form of vestibular pathology may have that condition exacerbated by age-related losses of vestibular functions. The effects of vestibular rehabilitation gaze stability exercises in patients with vestibular dysfunction are well established and include both improved dynamic acuity and postural stability. Improvements in posture control following rehabilitation of the vestibulo-ocular reflex are apparently due to improved peripheral and/or central vestibular balance control which has occurred in conjunction with enhanced gaze stability. The complex nature of increased fall risk suggests that an interdisciplinary approach to rehabilitation that includes vestibulo-ocular reflex rehabilitation appears likely to be associated with optimum outcomes for both pathological and age-related cases.

Applications of dynamic visual acuity test in clinical ophthalmology

Dynamic visual acuity test (DVAT) plays a key role in the assessment of vestibular function, the visual function of athletes, as well as various ocular diseases. As the visual pathways conducting dynamic and static signals are different, DVATs may have potential advantages over the traditional visual acuity tests commonly used, such as static visual acuity, contrast sensitivity, and static perimetry. Here, we provide a review of commonly applied DVATs and their several uses in clinical ophthalmology. These data indicate that the DVAT has its unique clinical significance in the evaluation of several ocular disorders.

Leveraging virtual reality for vestibular testing: Clinical outcomes from tests of dynamic visual acuity

BACKGROUND: Virtual reality (VR) use as a platform for vestibular rehabilitation is widespread. However, the utility of VR based vestibular assessments remains unknown. OBJECTIVE: To compare dynamic visual acuity (DVA) scores, perceived balance, and perceived dizziness when using traditional versus VR environments for DVA testing among healthy individuals. METHODS: DVA testing occurred for both a traditional clinical protocol and in a VR variant. Horizontal, vertical, and no head motion conditions were conducted for both clinical and VR test protocols. DVA scores, balance ratings, and dizziness ratings were obtained per condition. Two-way ANOVAs with repeated measures were used to assess differences in DVA scores, balance, and dizziness ratings. RESULTS: No differences in DVA results, balance or dizziness ratings were observed when comparing traditional clinical protocol versus the VR variant. Differences across head motion conditions were observed, with no motion trials exhibiting significantly higher DVA scores and perceived balance, and lower perceived dizziness compared to vertical and horizontal head motion. Vertical head motion exhibited this same trend compared to horizontal. CONCLUSION: DVA testing conducted in VR demonstrated clinical utility for each measure. Effects of head motion were similar across test variants, indicating DVA testing in VR produces similar effects on vestibular function than traditional clinical testing. Additional research should be conducted to assess the feasibility of VR assessment in individuals with vestibular disorder.

Effects of caffeine ingestion on dynamic visual acuity: a placebo-controlled, double-blind, balanced-crossover study in low caffeine consumers

Background Acute caffeine ingestion has been associated with improvements in cognitive performance and visual functioning. The main objective of this study was to determine the effects of caffeine intake on dynamic visual acuity (DVA). Methods Twenty-one low caffeine consumers (22.5 ± 1.6 years) took part in this placebo-controlled, double-blind, and balanced crossover study. In two different days and following a random order, participants ingested either caffeine (4 mg/kg) or placebo, and DVA was measured after 60 min of ingesting the corresponding capsule. A recently developed and validated software (moV& test, V&mp Vision Suite, Waterloo, Canada) was used to assess DVA. Results We found a greater accuracy for both the horizontal and random motion paths of DVA after caffeine ingestion (p < 0.001 and p = 0.002, respectively). In regard to the speed of the response, our data revealed that caffeine intake was associated with a faster reaction time for horizontally (p = 0.012) but not for randomly (p = 0.846) moving targets. Also, participants reported higher levels of perceived activation after consuming caffeine in comparison to placebo (p < 0.001). Conclusions Our data suggest that caffeine intake (i.e., a capsule containing 4 mg/kg) has an ergogenic effect on DVA, which may be of special relevance in real-word contexts that require to accurately and rapidly detect moving targets (e.g., sports, driving, or piloting).

Clinical dynamic visual acuity in patients with cerebellar ataxia and vestibulopathy

Deterioration of dynamic visual acuity (DVA) as a result of impaired vestibulo-ocular reflex (VOR) has been well described in peripheral vestibulopathies, however, changes in DVA in patients with degenerative cerebellar ataxias (CA) and its relation to VOR impairment in these patients has not yet been evaluated. Our aim was to assess the alterations of DVA in CA and to evaluate its relation to vestibular function. 32 patients with CA and 3 control groups: 13 patients with unilateral and 13 with bilateral vestibulopathy and 21 age matched healthy volunteers were examined by clinical DVA test, VOR was assessed by video Head Impulse Test and caloric irrigation. The severity of ataxia in CA was assessed by Scale for the assessment and rating of ataxia (SARA). Relationship between DVA and vestibular function in CA patients was examined by linear regressions. DVA impairment was highly prevalent in CA patients (84%) and its severity did not differ between CA and bilateral vestibulopathy patients. The severity of DVA impairment in CA was linked mainly to VOR impairment and only marginally to the degree of ataxia. However, DVA impairment was present also in CA patients without significant vestibular lesion showing that central mechanisms such as impairment of central adaptation of VOR are involved. We suggest that the evaluation of DVA should be a standard part of clinical evaluation in patients with progressive CA, as this information can help to target vestibular and oculomotor rehabilitation.