Mind the Visual Discomfort: Assessing Event-Related Potentials as Indicators for Visual Strain in Head-Mounted Displays

TL;DR

The study addresses the challenge of objectively measuring visual discomfort in head-mounted displays by leveraging time-locked EEG markers. Using a within-subject design ($N=20$) with symmetrical and asymmetrical Gaussian blur across five stimulus conditions, the authors analyze ERP components $P1$, $N2$, and $P3$ at occipito-parietal sites to assess processing load and discomfort. The key finding is that $N2$ amplitude is sensitive to blur (reflecting increased cognitive effort), while $P1$ remains robust and $P3$ shows limited sensitivity, with aggregated blur conditions indicating higher processing load and reduced attentional resource allocation. The results support the feasibility of EEG-based automatic discomfort detection to enable real-time HMD adjustments, offering potential improvements in VR usability and user comfort.

Abstract

When using Head-Mounted Displays (HMDs), users may not always notice or report visual discomfort by blurred vision through unadjusted lenses, motion sickness, and increased eye strain. Current measures for visual discomfort rely on users' self-reports those susceptible to subjective differences and lack of real-time insights. In this work, we investigate if Electroencephalography (EEG) can objectively measure visual discomfort by sensing Event-Related Potentials (ERPs). In a user study (N=20), we compare four different levels of Gaussian blur in a user study while measuring ERPs at occipito-parietal EEG electrodes. The findings reveal that specific ERP components (i.e., P1, N2, and P3) discriminated discomfort-related visual stimuli and indexed increased load on visual processing and fatigue. We conclude that time-locked brain activity can be used to evaluate visual discomfort and propose EEG-based automatic discomfort detection and prevention tools.

Figures (8)

• Figure 1: Experimental Task. The task asked participants to interact with geometric stimuli. Initially, a primitive object appeared for 1.8 seconds and then disappeared. Subsequently, a sphere spawned at the center, and participants had to move it to where the object was last seen. This sequence was repeated with each new object appearing without any blur or with varying blur levels and symmetry (see \ref{['sec:ind_var']}).
• Figure 2: Experimental Stimuli for the Blur Level.
• Figure 3: Experimental Stimuli for the Symmetry Adjustment.
• Figure 4: Experimental Procedure. After obtaining informed consent, participants underwent various preliminary assessments, including stimulus sharpness evaluation, stereo vision test, and initial SSQ questionnaire. They then engaged in a series of rotation tasks divided into training (15 trials) and three main sessions (50 trials each), with trials randomized across conditions. Between sessions, participants evaluated stimuli, discomfort, and sharpness. The experiment concluded with a final SSQ questionnaire to reassess simulator sickness.
• Figure 5: ERP for all conditions. We display ERP waveforms from - .2 to 1.0 seconds relative to stimulus onset across different visual discomfort conditions, highlighting variations in P1, N2, and P3 components under various levels of blur and symmetry. The line plot illustrates differential impacts on ERP amplitudes: P1 (100-300 ms) shows minimal change across conditions, suggesting resilience in early visual processing; N2 (100-300 ms) amplitude decreases with increased blur, indicating enhanced conflict monitoring; P3 (300 - 600 ms) demonstrates varied responses, with subtle reductions suggesting a marginal impact on cognitive resource allocation under altered visual conditions.