Limiting Cybersickness in eXtended Reality

This commentary is offered by Dr. Kay M. Stanney and Claire Hughes of Design Interactive.

eXtended reality (XR) technologies are transforming how many organizations train and operate. These technologies span the gamut from fully immersive virtual worlds to augmentation holograms overlaid onto the real-world to mixed-reality solutions that fuse digital and physical entities.

Within the military, as the Synthetic Training Environment (STE) continues to be developed and the Defense Health Agency (DHA) aims to provide joint services with a medically ready force, in part by adopting STE solutions to address readiness gaps, the continuum of XR solutions is poised to be a training tool of choice. The use of XR technologies across the STE and other military innovation efforts is critically important, as XR applications can address key pain points through provision of highly effective training solutions, augmentation of day-to-day operational activities, and redefining soldier experiences to provide a decisive overmatch. By implementing XR within the STE and beyond, commanders can significantly cut costs, engage their soldiers in new and empowering ways, improve safety, and improve overall soldier lethality and survivability.

The prospects for XR in the joint forces are endless. Well, they will be once we fully understand and deal with cybersickness.

What is Cybersickness?

Cybersickness is a form of motion sickness that soldiers may experience during immersive exposure to XR technologies. Depending on the content and technology, 20-95% of soldiers may experience some level of symptoms, including headache, eyestrain, disorientation, sweating, nausea, and beyond. These symptoms can last from minutes to hours after exposure, with problematic and persistent after-effects, including unstable posture, visual maladaptation, and altered hand-eye coordination.

Sounds a bit like intoxication, right? In fact, the adverse after-effects associated with XR exposure can mimic alcohol-related impairments. While cybersickness is most often associated with virtual reality (VR), it is something that may affect soldiers in all types of immersive environments. The potential for cybersickness could significantly impact the adoption of XR technologies for the DoD if not adequately addressed and mitigated.

Is Cybersickness a Problem in AR?

While cybersickness has been researched and well characterized in VR, little is known regarding the extent to which it is problematic in augmented reality (AR). Typically, VR users, be they military or civilian, have experienced more symptoms on the disorientation to nausea end of the cybersickness spectrum, whereas it appears AR users may be more likely to experience oculomotor disturbances such as headache and eyestrain.

Though these latter symptoms may not sound debilitating, when AR headsets are worn for extended periods of time these symptoms may have a significant impact. How would you feel if you wore glasses with the wrong prescription all day? That is what long-duration AR use may feel like for some users. In fact, as indicated by Hughes et al. (2020), the oculomotor symptomatology associated with long-duration AR exposure may produce cybersickness severity levels comparable to highly provocative VR systems.

Additionally, when users start to experience severe cybersickness in VR, they tend to become nauseous and abort their exposure; thus, VR is oftentimes self-limiting. On the other hand, the headache and visual fatigue symptoms associated with AR exposure are familiar to display users of all sorts, and thus, even when severe, may not serve as an impetus to curtail long-duration immersion. For this reason, increased post AR exposure maladaptation effects (e.g., blurry vision, altered depth perception) could become common place.

If AR technology poses risks to post-exposure visual functioning, this could affect postural stability or hand-eye coordination and present a safety risk to the soldier. It is thus critically important to understand the physiological impacts of long-duration AR exposure and mitigate them where possible, to ensure the safety of soldiers and all AR users.

What Can Be Done?

While more research is needed to determine how best to address the cybersickness associated with AR exposure, the following suggestions provide a place to start:

Implement Usage Protocols

Limit initial exposure durations and allow an intersession recovery period by providing a break between exposures. A place to start may be to reference guidelines for computer displays and be more prudent about following them. It is generally recommended that computer users follow the 20-20-20 rule: every 20 minutes, focus on a real-world object off the display screen at least 20 feet away for at least 20 seconds, as well as take a 15-minute break for every 2 hours spent focused on a screen. As conventional computer displays do not pose the vergence-accommodation conflicts and perceptual distortions imposed by AR devices, this threshold may prove to be insufficient to ensure safety of long-duration AR exposure. It is important to determine the exposure duration-break ratio that allows a soldier’s body to readjust and recalibrate to the real-world after immersion in an AR device. This will be particularly important if a soldier is performing close-up tasks (<12 inches) in the AR headset, as long-duration AR exposure while performing close-up tasks would be anticipated to cause post-exposure dexterity issues. Make sure to assess such symptoms for their severity, as this could prove important to soldier safety post exposure.

Minimize Perceptual Distortions

Use of focus or depth cues (texture gradients, occlusion, shading, binocular disparity, etc.) are common in XR applications to create three-dimensional (3D) views that convey depth, but these focus cues can be deceiving as they often cause vergence-accommodation mismatches for the soldier since they generally specify the depth of the display instead of the 3D scene. However, these perceptual distortions can be minimized by those developing XR applications. By matching the simulated distance in the display and the focal distance as closely as possible, developers can diminish soldier discomfort in the head-worn display (Hoffman et. al, 2010).

DHA and other military and industry leaders aim to revolutionize training and operational support paradigms with XR technologies. Understanding the associated cybersickness risks and ways to manage them can assist in the design and development of important application guidelines and usage protocols. This is of importance because early research focused on the latest-generation of AR headsets has found that cybersickness symptoms in long-duration AR exposure may be as severe as and persist as long as some of the most provocative VR systems. Further, even though the cybersickness symptoms expected with AR (visual fatigue, headaches) maybe be less overtly incapacitating than those associated with VR (gastrointestinal distress, disorientation), they may be just as apt to compromise soldier safety.

By following some simple guidelines and understanding associated risks, militaries and other organizations can successfully adopt these innovative technologies and revolutionize their training and operational support programs to increase productivity and create a decisive overmatch.

About the Authors

Kay Stanney, PhD is CEO and Founder of Design Interactive, a woman-owned, small business focused on human-systems integration. She is a recognized leader in eXtended Reality systems, especially as they relate to training and cybersickness. In 2019, she was inducted into the National Academy of Engineering (NAE) for her contributions to "human factors engineering through virtual reality technology and strategic leadership". She received the 2006 IEEE Virtual Reality Technical Achievement Award from the IEEE Computer Society, an award designed to honor individuals for their seminal technical achievement in virtual and augmented reality.

Claire Hughes, MSis a Research Associate II in the eXtended Reality Division at Design Interactive (Orlando, Florida). Her focus is on emerging technology delivery to diverse stakeholders, including the Joint Program Committee and the Army Futures Command. She holds a Master of Science in Human Factors and Systems Engineering from Embry-Riddle Aeronautical University and a Bachelor of Science in Mathematics from Hillsdale College.

References

Hoffman, D., Girschick, A., Akeley, K., Banks, M. (2010). Vergence-accommodation conflicts hinder visual performance and cause fatigue. J Vis. 8(3): 33.1-3330. Doi: 10-1167/8.3.33.

Hughes C., Fidopiastis C., Stanney K., Bailey, P., and Ruiz, E. (2020). The Psychometrics of Cybersickness in Augmented Reality. Frontiers in Virtual Reality. 1:602954. doi: 10.3389/frvir.2020.602954.

Editor’s Note: From time to time, MS&T magazine presents Guest Commentary on important issues facing the community. The opinions expressed are the author’s own.