Virtual Reality offers immersive depth perception experiences. Stereoscopic visual fatigue is a significant obstacle currently hampering the development of virtual reality applications.
A recently published study in brain science investigates the fundamental neural mechanism of stereoscopic visual fatigue in virtual reality. A Go/NoGo model based on disparity variations has been proposed to induce stereoscopic visual fatigue associated with depth perception. Researchers investigated the influence of disparity variations and stereoscopic visual fatigue on the temporal properties of visual evoked potentials. Disparities, repeated measures, and point-by-point statistical permutation analyzes affect posterior visual evoked potentials according to analysis of variance (ANOVA) results.
Impact of Stereoscopic Visual Fatigue on Virtual Reality Applications
The development of stereoscopic displays, especially virtual reality, shows applications for deep immersion.
The properties of virtual reality are drastically affected by stereoscopic visual fatigue, which is a state of weakness, easy exhaustion, and unsustainable vision of an organ associated with vision. It develops as a result of high exposure after viewing stereoscopic content and may present as diplopia, blurred vision, and other symptoms of binocular abnormalities.
Several important visual health problems, including decreased retinal vision, dry eyes, optic neurasthenia, cataracts, and glaucoma, are associated with prolonged exposure to electronics-induced visual fatigue.
Stereoscopic visual fatigue assessment is crucial to advance stereoscopic display technology for more comfortable viewing. Vergence-accommodation conflict (VAC) and high binocular disparity contribute to stereoscopic visual fatigue.
The efficiency of the visually evoked potential
Visually evoked potentials are one of the most valuable and dynamic methods to track the neural flow of information in real time. Visually evoked potentials are typically extracted from scalp-recorded electroencephalography (EEG) by signal averaging and temporally linked to perception and specific visual sensory events.
Visual evoked potentials are predicted to be used as an objective measure of response to visual stimuli. In recent years, they have therefore developed into one of the most efficient techniques for examining human visual cognitive function.
Variations in the properties of typical visually evoked potential components indicate functional changes in specific neural regions because they can be used as indicators to represent a specific process of visual information perception. Variations in disparity trigger visually evoked potentials.
Investigating the Neural Mechanisms of Stereoscopic Visual Fatigue
guo et al. developed an experimental model based on the Go/NoGo by a head-mounted display to study the brain mechanism of stereoscopic visual fatigue. Variations in disparity with vergence-accommodation conflict led to the induction of stereoscopic visual fatigue. The Go/NoGo model was developed to keep respondents’ attention levels high during the stereoscopic visual fatigue experiment, as it is typically used to assess participants’ ability for sustained attention and response control.
Random dot stereograms (RDSs) were used as visual stimuli to isolate the disparity variations, allowing the analysis to identify the time domain characteristics of visual evoked potentials. The association between disparities and the characteristics of the components of the visual evoked potentials, as well as the relationship between stereoscopic visual fatigue and these same qualities, were examined using point-by-point statistics and a one-way repeated measures analysis of variance (ANOVA).
Participants and research environment
Six men and eight women, a total of 14 healthy right-handed adults (aged 24 ± 1.1 years), were selected for the study from a group of graduate students at the Beijing Institute of Technology (Beijing, China). Participants had no degenerative, psychiatric, or neurological conditions known to affect cognition, normal corrected, or normal stereoscopic vision. Each participant signed an informed consent form after receiving the complete information.
Participants were accommodated in a quiet room with excellent air conditioning and a comfortable, height-adjustable chair. As a display unit, the HTC Vive Pro Head-Mounted Display (HMD) was used, which has two displays (one for each eye), each of which is a 3.5-inch AMOLED with a resolution of 1440 * 1600 pixels. The horizontal field of view (FOV) of the HMD was 110 and the refresh rate was 90 Hz. During the experiment, participants were required to wear a 64-electrode Compumedics NeuroScan EEG headgear. Instead of being worn on participants’ heads during EEG collection, the HMD was mounted on a movable mechanical arm to minimize interference.
In this study, Guo et al. developed a Go/NoGo paradigm to maintain focus and created the first experimental stereoscopic visual fatigue scenario caused by disparity variations in a visual reality environment. The temporal characteristics of visual evoked potentials induced by disparity shifts were measured using RDSs as the visual stimulus. Point-by-point statistics and one-way repeated measures ANOVA were used to examine the association between disparities/stereoscopic visual fatigue and the properties of the visual evoked potentials component.
Researchers found that disparity variations caused posterior visually evoked potential components to be triggered. This proved that posterior visual evoked potentials originating from the precuneus might be related to depth perception, reflecting the neural response to vergence during depth perception.
The main finding of this study is that posterior visual evoked potentials can be a valuable indicator for the assessment of stereoscopic visual fatigue as well as an indicator of the disparity variance separating comfort from pain in visual reality content.
Guo M, Yue K, Hu H, Lu K, Han Y, Chen S, & Liu Y (2022) Neural Research on Depth Perception and Stereoscopic Visual Fatigue in Virtual Reality . brain science, 12(9), 1231. https://www.mdpi.com/2076-3425/12/9/1231