Impaired Subjective Visual Vertical and Increased Visual Dependence in Older Adults With Falls

Subclinical variability in visual function modulates visual dependence - independent of age

Paradoxically visual dependence is reported to increase with age, contributing to falls risk, whereas visual function typically declines. This study assesses the relationship between age, objective and subjective measures of visual function and visual dependence, in healthy young and older adults. Forty-four healthy Young (YA; n = 32; 18 males, aged 26.2 ± 5.3 yrs.) and Older (OA; n = 12; 3 males, aged 62.4 ± 6.7 yrs.) adults were assessed for objective (visual acuity, contrast sensitivity, depth perception, and lower peripheral vision), and subjective visual function (VFQ-25) along with motion sickness susceptibility. Subjective Visual Vertical (SVV) and induced nausea and vection were assessed using the Rod and Disc Test (RDT). Groups were compared using Mann-Whitney U, whilst determinants of SVV variability were evaluated using Multiple regression modelling. Visual acuity (p < 0.01) and contrast sensitivity (p = 0.04) were lower in OA. Visual dependence (SVV tilt errors) was not associated with ageing (p = 0.46). YA experienced greater RDT-induced vection (p = 0.03). Visual acuity and contrast sensitivity accounted for modest proportions of variance in SVV tilt errors (VA; R2 = 0.14, F(1,42) = 8.00, p < 0.01; β = 6.37) and (CS; R2 = 0.06, F(1,42) = 3.93, p = 0.05; β = -4.97), respectively. Our findings suggest that subclinical differences in visual acuity and contrast sensitivity contribute to SVV tilt error variability, among both healthy young and older adults. Further studies are needed to define the inter-relationship between age-related visual function, non-visual factors (including vestibular and somatosensory fidelity, activity levels, fear of falling and cognitive function) and visual dependence.

Visual Field Dependence Persists in Age-Related Central Visual Field Loss

Purpose

To examine whether the age-related increase in visual field dependence persists in older adults with central field loss (CFL).

Methods

Twenty individuals with CFL were grouped into participants with age-related binocular CFL (CFL, n = 9), age-related monocular CFL/relative scotomata (mCFL, n = 8), and CFL occurring at a young age (yCFL, n = 3). Seventeen controls were age-matched to the older CFL groups (OA) and three to the yCFL group (yOA). Participants judged the tilt direction of a rod presented at various orientations under conditions with and without a visual reference. Visual field dependence was determined as the difference in judgment bias between trials with and without the visual reference. Visual field dependence was examined between groups and relative to visual acuity and contrast sensitivity.

Results

All older groups performed similarly without the visual reference. The CFL group showed greater visual field dependence than the OA group (Mann-Whitney U test; U = 39, P = 0.045). However, there was no group difference when considering all three older groups (Kruskal-Wallis ANOVA; H(2, N = 34) = 4.31, P = 0.116). Poorer contrast sensitivity correlated with greater visual field dependence (P = 0.017; ρ = -0.43).

Conclusions

Visual field dependence persists in older adults with CFL and seems exacerbated in those with dense binocular scotomata. This could be attributed to the sensitivity of the spared peripheral retina to orientation and motion cues. The relationship with contrast sensitivity further suggests that a decline in visual function is associated with an increase in visual field dependence beyond the effects of normal aging. These observations can guide tailored care and rehabilitation in older adults with CFL.

Concentrating to avoid falling: interaction between peripheral sensory and central attentional demands during a postural stability limit task in sedentary seniors

Evidence suggests falls and postural instabilities among seniors are attributed to a decline in both the processing of afferent signals (e.g., proprioceptive, vestibular) and attentional resources. We investigated the interaction between the non-visual and attentional demands of postural control in sedentary seniors. Old and young adults performed a postural stability limit task involving a maximal voluntary leaning movement with and without vision as well as a cognitive-attentional subtraction task. These tasks were performed alone (single-task) or simultaneously (dual-task) to vary the sensory-attentional demands. The functional limits of stability were quantified as the maximum center of pressure excursion during voluntary leaning. Seniors showed significantly smaller limits of postural stability compared to young adults in all sensory-attentional conditions. However, surprisingly, both groups of subjects reduced their stability limits by a similar amount when vision was removed. Furthermore, they similarly decreased their anterior-posterior stability limits when concurrently performing the postural and the cognitive-attentional tasks with vision. The overall average cognitive performance of young adults was higher than seniors and was only slightly affected during dual-tasking. In contrast, older adults markedly degraded their cognitive performance from the single- to the dual-task situations, especially when vision was unavailable. Thus, their dual-task costs were higher than those of young adults and increased in the eyes-closed condition, when postural control relied more heavily on non-visual sensory signals. Our findings provide the first evidence that as posture approaches its stability limits, sedentary seniors allot increasingly large cognitive attentional resources to process critical sensory inputs.

The temporal precision of audiovisual integration is associated with longitudinal fall incidents but not sensorimotor fall risk in older adults

Sustained multisensory integration over long inter-stimulus time delays is typically found in older adults, particularly those with a history of falls. However, the extent to which the temporal precision of audio-visual integration is associated with longitudinal fall or fall risk trajectories is unknown. A large sample of older adults (N = 2319) were grouped into longitudinal trajectories of self-reported fall incidents (i.e., decrease, stable, or increase in number) and, separately, their performance on a standard, objective measure of fall risk, Timed Up and Go (TUG; stable, moderate decline, severe decline). Multisensory integration was measured once as susceptibility to the Sound-Induced Flash Illusion (SIFI) across three stimulus onset asynchronies (SOAs): 70 ms, 150 ms and 230 ms. Older adults with an increasing fall number showed a significantly different pattern of performance on the SIFI than non-fallers, depending on age: For adults with increasing incidents of falls, those aged 53-59 years showed a much smaller difference in illusion susceptibility at 70 ms versus 150 ms than those aged 70 + years. In contrast, non-fallers showed a more comparable difference between these SOA conditions across age groups. There was no association between TUG performance trajectories and SIFI susceptibility. These findings suggests that a fall event is associated with distinct temporal patterns of multisensory integration in ageing and have implications for our understanding of the mechanisms underpinning brain health in older age.

Perceptual visual dependence for spatial orientation in patients with schizophrenia

BACKGROUND

Patients with schizophrenia are reported to have vestibular dysfunction and to weigh vestibular input to a lesser extent compared to healthy controls. Such deficits may increase visual dependence (VD) for spatial orientation at a perceptual level in these patients. The aim of this study is to compare VD levels between healthy control and patients with schizophrenia and to explore associations between VD and clinical measures in these patients. Relation of VD to antipsychotic drug treatment is also discussed.

METHOD

18 patients with schizophrenia and 19 healthy controls participated in this study. The Rod and Disc Test (RDT) was used to create an optokinetic surround around a centrally located rod. Participants aligned the rod to their subjective visual vertical (SVV) in both static and dynamic disc conditions. VD was calculated as the difference in SVV between these two conditions.

RESULTS

There was no group difference or gender difference in static or dynamic SVV as well as VD. There was no correlation between VD and any of the Positive and Negative Syndrome Scale (PANSS) scores, however VD was significantly correlated to illness duration in the patient group.

CONCLUSIONS

Schizophrenia is not associated with greater VD levels at a perceptual level, compared to controls, indicating adequate visuo-vestibular integration for judging line verticality in these patients. Patients with greater chronicity of the disease are more visually dependent than those less chronically ill, consistent with previous reports of possible vestibular dysfunction in patients with schizophrenia. This may affect their daily functioning in dynamic visual environments.

[The effect of different rotation modes on testing resulting of the subjective visual vertical]

Objective:To investigate the effect of different rotations modes of control rod on testing results of the subjective visual vertical （SVV）. Methods:Twenty-four normal young volunteers were selected for this study, and the control rod of SVV was rotated in clockwise, counterclockwise and any direction at the head tilt-positions of 0°, 45° left and 45° right. The differences of SVV deflection angle values at different rotation modes were analyzed. Results:①The deviation angle values of SVV obtained by rotating the control rod in clockwise, counterclockwise and any direction at the head tilt-positions of 0° were 1.56°±0.21°, 3.05°±0.24°, and 2.16°±0.22°, respectively，and the difference was statistically significant （P<0.05）,the deviation angle value of SVV in clockwise direction was smaller; ②At head tilt-positions of 45° left, the SVV deviation angle values obtained by rotating the control rod in three rotation modes were 2.59°±0.53°, 4.03°±0.51°, and 3.49°±0.54°, respectively, and the difference was statistically significant（P<0.05）,the deviation angle value in the clockwise direction was also smaller; ③At the head tilt-positions of 45° right, the SVV deviation angle values in three modes were 4.68°±0.58°, 7.23°±0.72°, and 5.93°±0.96°, respectively, and the difference was statistically significant （P<0.05）,the deviation value of SVV was also smaller when rotated in the clockwise direction; ④Comparison of SVV deviation angle values in three rotation modes at the head tilt-positions of 45° left and 45° right showed that there was no statistical difference in clockwise and in any direction （P>0.05）, while the difference was statistically significant when rotated in the counterclockwise direction （P<0.05）. Conclusion:Different rotation modes of the control rod during SVV testing will affect the test results. Rotating the control rod in clockwise direction to make the SVV values more accurate is recommended.

A Cross-Sectional Study on the Effect of Chronic Noise Exposure on the Vestibular Function of Traffic Policemen and Automobile Drivers

Introduction

Noise is a preventable occupational hazard for certain professions like automobile drivers and traffic police personnel. The harmful auditory effects of noise are well known. However, little is known about the status of the vestibular function in chronic noise exposure without noise induced hearing loss. Our objective was to assess the vestibular function in chronic noise exposure.

Methodology

: The study was conducted with a sample size of 242 (chronic noise exposure group - 121, group without chronic noise exposure - 121). Noise estimation was carried out across various traffic intersections to assess the noise exposure levels of the exposed group. All participants underwent a detailed vestibular evaluation in the clinical vestibulometry laboratory.

Results

There was no difference in nystagmus, saccades, caloric function between the two groups. The latency and amplitude of vestibular evoked myogenic potentials (VEMP) were similar in both the groups. However, dynamic posturography showed a significant difference in the Adaptation test between the two groups (P < 0.05). We also found a statistically significant difference between the static and dynamic subjective visual vertical (SVV) and the dynamic visual acuity (DVA) between the two groups (P < 0.05).

Conclusion

We did not find any clinical evidence of vestibular dysfunction in the noise exposed group. However, the statistical significance of SVV and DVA as seen in this study needs to be evaluated further as an early marker for vestibular dysfunction. It remains to be seen whether the statistically significant prolongation is reversible after the noise exposure is withdrawn.

Subjective visual vertical imprecision during lateral head tilt in patients with chronic dizziness

Most prior studies of the subjective visual vertical (SVV) focus on inaccuracy of subjects' SVV responses with the head in an upright position. Here we investigated SVV imprecision during lateral head tilt in patients with chronic dizziness compared to healthy controls. Forty-five dizzy patients and 45 healthy controls underwent SVV testing wearing virtual reality (VR) goggles, sitting upright (0°) and during head tilt in the roll plane (± 30°). Ten trials were completed in each of three static head positions. The SVV inaccuracy and SVV imprecision were analyzed and compared between groups, along with systematic errors during head tilt, i.e., A-effect and E-effect (E-effect is a typical SVV response during head tilts of ± 30°). The SVV imprecision was found to be affected by head position (upright/right head tilt/left head tilt, p < 0.001) and underlying dizziness (dizzy patients/healthy controls, p = 0.005). The SVV imprecision during left head tilt was greater in dizzy patients compared to healthy controls (p = 0.04). With right head tilt, there was a trend towards greater SVV imprecision in dizzy patients (p = 0.08). Dizzy patients were more likely to have bilateral (6.7%) or unilateral (22.2%) A-effect during lateral head tilt than healthy controls (bilateral (0%) or unilateral (6.7%) A-effect, p < 0.01). Greater SVV imprecision in chronically dizzy patients during head tilts may be attributable to increased noise of vestibular sensory afferents or disturbances of multisensory integration. Our findings suggest that SVV imprecision may be a useful clinical parameter of underlying dizziness measurable with bedside SVV testing in VR.