Explaining Self-Motion Perception using Virtual Reality in Patients with Ocular Disease

Safe mobility requires accurate object and self-motion perception. This involves processing retinal motion generated by optic flow (which change with eye and head movements) and correctly integrating this with vestibular and proprioceptive cues. Poor sensory feedback of self-motion can lead to increased risks of accidents which impacts quality of life. This is further problematic for those with visual deficits, such as central or peripheral vision loss or impaired binocular vision. The expansion of healthcare into using virtual reality (VR) has allowed the assessment of sensory and motor performance in a safe environment. An advantage of VR is its ability to generate vection (perceived illusory self-motion) and presence (sense of being ‘there’). However, a limitation is the potential to develop cybersickness. Initially, the project examined how binocular vision influences vection in a virtual environment. Observers with or without stereopsis (ability to judge depth binocularly) were asked to compare their perceptual experiences based on psychophysical judgements of magnitude estimation. The findings suggest that the absence of stereopsis impairs accurate judgement of self-motion and reduces perceived presence, however, it was protective for cybersickness. The project then examined the impact of central and peripheral vision loss on self-motion perception by comparing those with age-related macular degeneration (AMD) and glaucoma respectively. Effects of these visual deficits on sensory conflicts involving visual-vestibular interactions was then assessed. Sensory conflict was imposed by altering the gain of simulated head linear head position and angular orientation to be either compatible or incompatible with head movement in two separate experiments. Fixation was used to control gaze during changes in angular head orientation. Vection and presence was higher in those with AMD, compared with those with glaucoma, indicating the importance of regional specificity in visual deficits on self-motion perception. Across studies, vection and presence were predominantly visually mediated despite changes in visual-vestibular sensory conflict. The vestibular system, however, appeared to play a larger role in developing cybersickness. The altered perception of self-motion may worsen mobility, particularly with disease progression. We therefore provide a framework and recommendations for a multidisciplinary patient-centric model of care to maximise quality of life

Evaluation of Detecting Cybersickness via VR HMD Positional Measurements Under Realistic Usage Conditions.

With the resurgence of virtual reality, head-mounted displays (VR HMD) technologies since 2015, VR technology is becoming ever more present in people's day-to-day lives. However, one significant barrier to this progress is a condition called cybersickness, a form of motion sickness induced by the usage of VR HMD’s. It is often debilitating to sufferers, resulting in symptoms anywhere from mild discomfort to full-on vomiting. Much research effort focuses on identifying the cause of and solution to this problem, with many studies reporting various factors that influence cybersickness, such as vection and field of view. However, there is often disagreement in these studies' results and comparing the results is often complicated as stimuli used for the experiments vary wildly. This study theorised that these results' mismatch might partially be down to the different mental loads of these tasks, which may influence cybersickness and stability-based measurement methods such as postural stability captured by the centre of pressure (COP) measurements. One recurring desire in these research projects is the idea of using the HMD device itself to capture the stability of the users head. However, measuring the heads position via the VR HMD is known to have inaccuracies meaning a perfect representation of the heads position cannot be measured. This research took the HTC Vive headset and used it to capture the head position of multiple subjects experiencing two different VR environments under differing levels of cognitive load. The design of these test environments reflected normal VR usage. This research found that the VR HMD measurements in this scenario may be a suitable proxy for recording instability. However, the underlying method was greatly influenced by other factors, with cognitive load (5.4% instability increase between the low and high load conditions) and test order (2.4% instability decrease between first run and second run conditions) having a more significant impact on the instability recorded than the onset of cybersickness (2% instability increase between sick and well participants). Also, separating participants suffering from cybersickness from unaffected participants was not possible based upon the recorded motion alone. Additionally, attempts to capture stability data during actual VR gameplay in specific areas of possible head stability provided mixed results and failed to identify participants exhibiting symptoms of cybersickness successfully. In conclusion, this study finds that while a proxy measurement for head stability is obtainable from an HTC Vive headset, the results recorded in no way indicate cybersickness onset. Additionally, the study proves cognitive load and test order significantly impact stability measurements recorded in this way. As such, this approach would need calibration on a case-by-case basis if used to detect cybersickness

Evaluation of cybersickness in virtual reality in driving simulator

Virtual reality (VR) devices are becoming a more popular and widespread tool for learning, gaming and entertainment purposes. One of familiar problems of emerging in VR is side effect known as cybersickness, which can be a nuisance for consumers of VR content. This occurrence can be explained as visual and vestibular conflict. The problem with cybersickness lies within the fact that the body is stationary, but eyes perceive motion in virtual reality, also known as vection. Cybersickness symptoms that often occur include blurred vision, headache, vertigo, upset stomach and other. Aim of this research is to observe changes in cybersickness symptoms in two tested conditions (2D display and VR). In this paper, subjective and objective metric of evaluation regarding cybersickness in VR driving simulation are used. Subjective metric is survey and objective metric is electroencephalogram (EEG). Results of the survey indicate which symptoms of cybersickness are more pronounced during driving in virtual environment compared with classic 2D screen experience. Statistically significant difference was found for 6 variables, which include vertigo, blurred vision and headache. Objective metric showed that highest average beta wave was in VR setting, as well as beta/alpha ratio, which is associated with stress and excitement

The effect of visual detail on cybersickness:predicting symptom severity using spatial velocity

Abstract. In this work, we examine the effect of visual realism on the severity of cybersickness symptoms experienced by users of virtual environments. We also seek to validate a metric called spatial velocity as a predictor of cybersickness. The proposed metric combines the visual complexity of a virtual scene with the amount of movement within the scene. To achieve this, we prepared two virtual scenes depicting the same environment with a variable level of detail. We recruited volunteers who were exposed to both scenes in two separate sessions. We obtained the sickness ratings after both sessions and saved the data required for spatial velocity calculations. After comparing the sickness ratings between the two scenes, we found no evidence of the visual realism playing any significant role in the generation of cybersickness symptoms. The spatial velocity also proved inadequate in characterizing the difference in visual complexity and correlated poorly with all the observed sickness scores.Visuaalisen yksityiskohtaisuuden vaikutus VR-pahoinvointiin : oireiden vakavuuden ennustaminen käyttäen SV-metriikkaa. Tiivistelmä. Tässä työssä tutkimme sitä, millainen vaikutus virtuaalisten ympäristöjen graafisella yksityiskohtaisuudella on VR-pahoinvointiin. Pyrimme myös validoimaan "spatial velocity" -nimisen mittasuureen kyvyn ennustaa VR-pahoinvoinnin oireiden vakavuutta. Kyseisen mittasuureen etuna on, että se yhdistää visuaalisen kompleksisuuden ja ympäristössä koetun liikkeen yhdeksi suureeksi. Tutkimusta varten valmistimme kaksi virtuaaliympäristöä, joissa mallinnettiin Oulun yliopiston kampusaluetta. Toinen ympäristö pyrki mahdollisimman realistiseen esitystapaan, kun taas toisessa yksityiskohtien määrä minimoitiin. Koetta varten värväsimme 18 vapaaehtoista. Vapaaehtoiset altistettiin kummallekin ympäristölle kahdessa noin kymmenen minuutin mittaisessa kokeessa. Vapaaehtoisten kokeman VR-pahoinvoinnin vakavuutta arvioitiin kunkin kokeen jälkeen täytetyillä kyselylomakkeilla. Kokeiden aikana tallensimme myös SV laskentaan tarvittavat tiedot. Verrattuamme koeolosuhteiden tuloksia, emme löytäneet todisteita siitä, että ympäristön graafisten yksityiskohtien määrällä olisi merkittävää vaikutusta koettuun pahoinvointiin. Käytetty SV metriikka ei myöskään kyennyt erottelemaan ympäristöjä oletetulla tavalla, eivätkä lasketut arvot korreloineet merkittävästi minkään mitatun pahoinvointisuureen kanssa

Vection in virtual reality modulates vestibular‐evoked myogenic potentials

The popularity of virtual reality (VR) has increased rapidly in recent years. While significant technological advancements are apparent, a troublesome problem with VR is that between 20% and 80% of users will experience unpleasant side effects such as nausea, disorientation, blurred vision and headaches—a malady known as Cybersickness. Cybersickness may be caused by a conflict between sensory signals for self-motion: while vision signals that the user is moving in a certain direction with certain acceleration, the vestibular organs provide no corroborating information. To resolve the sensory conflict, vestibular cues may be down-weighted leading to an alteration of how the brain interprets actual vestibular information. This may account for the frequently reported after-effects of VR exposure. Here, we investigated whether exposure to vection in VR modulates vestibular processing. We measured vestibular-evoked myogenic potentials (VEMPs) during brief immersion in a vection-inducing VR environment presented via head-mounted display. We found changes in VEMP asymmetry ratio, with a substantial increase in VEMP amplitude recorded on the left sternocleidomastoid muscle following just one minute of exposure to vection in VR. Our results suggest that exposure to vection in VR modulates vestibular processing, which may explain common after-effects of VR

Sensory Conflict: Effects on the Perceived Onset of Motion and Cybersickness in Virtual Reality

The perception of self-motion involves the integration of multisensory information, however there are scenarios in which the sensory feedback we receive from these different sources can conflict with one another. For example, when inside the cabin of a ship at sea or playing a game in virtual reality (VR), sensory signals for self-motion from the visual and vestibular systems may not be congruent. It has been well documented that such scenarios are associated with feelings of discomfort and alterations in our perception of motion, but the mechanisms leading to these perceptual consequences remain uncertain. The goal of this dissertation is to explore the effect of sensory conflict between vestibular and visual signals on the perception of self-motion and implications for cybersickness. Chapter Two examined the effect of sensory conflict on the perceived timing of a passive whole-body rotation paired with both congruent and incongruent visual feedback using VR. It was found that the visual signal only influenced the perception of movement onset when the direction of the visual motion did not match the expected equal and opposite response relative to physical rotation. In Chapter Three, the effect of sensory conflict between visual, vestibular and body cues on the perceived timing of visual motion was explored. The results revealed that changing the orientation of the body relative to gravity to dissociate the relationship between vestibular and body cues of upright delays the perceived onset of visual yaw rotation in VR by an additional 30ms compared to an upright posture. Lastly, Chapter Four investigated the relationship between sensory conflict and sensory reweighting through measures of cybersickness and sensory perception after exposure to VR gameplay. The results indicated that the perception of subjective vertical was significantly influenced by an intense VR experience and that sensory reweighting may play a role in this effect, along with providing a potential explanation for individual differences for cybersickness severity. Altogether, this dissertation highlights some of the perceptual consequences of sensory conflict between vestibular and visual signals and provides insights for the potential mechanisms that determine the perception of self-motion and cybersickness in VR

A Somatic Approach to Combating Cybersickness when using Head-Mounted Displays

This thesis presents a novel approach for reducing the risk of cybersickness during virtual reality locomotion in a 3D environment through the use of somatosensory feedback. This project looks directly at existing theories regarding the cause of cybersickness and describes the processes taken to develop, test and measure the efficacy of a solution. The solution proposed by this thesis builds on the concept of sensory misalignment, where the body struggles understand its state due to conflicting sensory feedback and consequently generates negative health symptoms and discomfort. As such, the studies in this project attempt to emulate the feedback of real movement during VR locomotion by artificially generating the passive airflow undergone whilst moving. To evaluate the work, two studies are carried out where users drive a simulated car around a virtual environment, which in one condition is accompanied by the solutions dynamic airflow emulation equipment. Primarily, studies examine for cybersickness, however on-going discussions in the research community regarding the nature of correlation between sickness and presence present interesting insights that this project could contribute to. The project’s pilot study failed to find conclusive results but provided a major amount of information about the correct strategies to use when investigating this exploratory area. A second study was far more successful, providing conclusive results showing that users felt less sickness and increased presence during the session supported by the somatic feedback extension. As such this work concludes suggesting somatosensory feedback has positive interactions with cybersickness, as per the project hypothesis regarding existing theories. Additionally, positive correlations with presence suggest somatic feedback can have an overall positive effect on VR locomotion

Movement Modalities in Virtual Reality: A Case Study from Ocean Rift Examining the Best Practices in Accessibility, Comfort, and Immersion

The visceral immersion of virtual reality (VR) requires that developers rethink how we design, model, and interact with virtual worlds. One of the most important considerations is how the user moves around, and this has led to several movement modalities with various levels of abstraction. In this article, we explore movement modalities in the VR and examine how the various systems differ in terms of accessibility, comfort, and immersion. We then provide a case study on how we used these best practices in developing our underwater safari park experience Ocean Rift, which is one of the most popular VR applications across personal computers and mobile VRs