Virtual-reality (VR) describes technologies trying to accurately simulate a virtual environment with the use of Virtual-Reality-Headsets or Virtual-Reality-Head-Mounted-Displays (VRHMDs). These devices typically consist of a screen with lenses mounted in front of the user’s eyes and additional motion sensors inside of the device. The headset is worn like a pair of ski-goggles and is often connected to a computer which renders a three-dimensional (3D) world to the user’s eyes. The main difference to “conventional” 3D movies is that the computer uses the input of the motion sensors – and in newer devices additional external tracking hardware – to continuously update the information on the user’s head position and orientation to adjust the displayed image. Modern devices like the HTC-Vive manage to do these updates about every 22ms (Luckett 2018). These factors combined allow the user to naturally look around, walk around and even interact with a virtual world and can create a feeling of being “present” in a different location, immersing the user in the displayed content.

While the most obvious use case for this technology is probably the entertainment and gaming sector, VR has gained significant traction in professional fields, such as medicine as well.

There are numerous use cases for VR in medicine, some of the most exciting are the usage of VR for realistic training of surgical procedures, to simulate more realistic 3D-imaging, in preoperative planning and even for remote surgical operations (Boedecker et al. 2021; Ghaednia et al. 2021; Mishra et al. 2022; Verhey et al. 2020).

Furthermore, VR can assist in phobia treatment by exposing patients to controlled anxiety-inducing scenarios(Park et al. 2019; Salehi et al. 2020). For example, patients with a fear of spiders can be exposed to virtual spiders(Hinze et al. 2021; Lindner et al. 2020). Patients with a fear of heights can virtually experience standing on the edge of a skyscraper to become more comfortable with the situation while still knowing that they are actually safe on the ground (Rimer et al. 2021). It has also been shown that VR can help to easier and more objectively diagnose specific phobias in patients by having them navigate an automated VR-program and analyzing their behavior (Binder et al. 2022; Lindner et al. 2020).

VR has also been shown to be beneficial in the rehabilitation of stroke patients, significantly increasing the balance of patients when including VR-therapy in the rehabilitation process.(Jung et al. 2012; Kim et al. 2015, 2016; Voinescu et al. 2021).

Apart from medical applications, other professional examples are construction companies that use the technology to visualize building concepts (Ashgan et al. 2023; Ghobadi & M.E. Sepasgozar, 2020), car manufacturers and designers who assess the overall impact of a planned car design without the need to construct expensive prototypes (de Clerk et al. 2019; Gong et al. 2020; Lawson et al. 2016) and much more.

As this exciting technology matures and becomes more broadly available, the use cases and therefore the adoption is expected to increase more and more. Recently Apple – one of the largest manufacturers of computers and largest company in the world (Randewich and Datta 2023; Statista 2023) - announced their first VRHMD with an obvious focus on productivity applications(Apple 2023; Nieva & Cai, 2023). With the adoption of this technology increasing, it becomes also more important to be aware of potential risks and problems based on this technology.

A key aspect of using virtual reality is movement: the ability to move around objects, look at them from different perspectives and possibly interact with them. This can quickly become a problem if the physical space available to a user is smaller than the simulated space needs to be to effectively experience the simulated environment. For example, if a surgical operation should be simulated but the user only has a small room available, the user would potentially not be able to walk around the virtual operating table without colliding with real life objects such as walls, a desk etc. without dedicating a large space solely for the purpose of VR-demonstration. In order to bypass this restriction, artificial movement (AM) is often used in VR, meaning the simulated viewpoint is moved in a way that does not correspond 1:1 to a physical movement in the real world.

There are many different approaches to implement AM in VR. The most common methods are floating movement and teleportation.

Floating movement describes a gradual transfer of the simulated viewpoint from one point to another while the user is standing still.

Teleportation on the other hand refers to an instantaneous change of the camera position from one point to another.

While solving the problem of limited space, AM can introduce new problems such as Simulator Sickness (SS).

SS is a complex of 16 symptoms such as nausea, headaches, vomiting and was originally described for users of flight simulators, but SS can also occur when using VR applications (Kennedy et al. 1993). Previous research suggests that the occurrence of SS in VR is the result of a variety of reasons, with one of the main factors being artificial movement (Bimberg et al. 2020; Christou and Aristidou 2017; Duzmanska et al. 2018; Kolasinski 1995; Rebenitsch and Owen 2016; Saredakis et al. 2020; So et al. 2001; Stanney et al. 2020; Vlahovic et al. 2018).

Previous research has also found, that the effects of SS can last well beyond the the initial exposure, especially if users experience high levels of SS. Notably Bos et al. reported in 2005 that some users took more than 2 h to recover from SS symptoms after being exposed to virtual ship movement (Bos et al. 2005).

The medical significance of VR lies therefore not only in its use cases in the medical field, but with the expected increase in adoption of VR and therefore its growing user base, it becomes increasingly important to be aware of potential adverse side effects the technology might bring to users.

Especially with VR being increasingly used in critical environments such as healthcare, it is important to conduct proper testing of the causes of SS in VR. For example, it would obviously be unfavorable if a surgeon were to use VR as a last-minute preparation for a surgery only to be impaired by symptoms of SS afterwards while attempting to perform the procedure.

The importance of avoiding SS in VR becomes even more critical when developing tools for patient intervention. For example as mentioned before, VR is being used in stroke patient rehabilitation (Kim et al. 2015; Montoya et al. 2022; Voinescu et al. 2021). However, it is well known that stroke patients often struggle with impaired balance (Bonan et al. 2013; Yelnik et al. 2006). While this might be a reason why VR-interventions benefit stroke patients in the first place, it is important to control the level of challenge to the vestibular system created by the VR software. This way the benefits for patients can be maximized while avoiding an unwanted occurrence of SS, which might reduce patient acceptance or the outcome of the treatment.

Consequently, this leads to the question what is the most suitable way to implement artificial movement without causing SS in users and how can it be properly evaluated?

Most of the research done on the topic of SS in VR uses commercially available games or assets intended to be used for action games (Farmani and Teather 2020; Saredakis et al. 2020; Yildirim 2020). This poses a potential source for errors in testing since games are meant to entertain and excite the user. The excitement or stress of playing a game however might skew the results since stress symptoms caused by the game content might be mistaken for symptoms of SS (Saredakis et al. 2020).

Saredakis et al. conducted a large study on the effects of content on the occurrence of SS in VR applications. They found that content which they classified as scenic or minimalistic produced significantly lower levels of SS than gaming content(Saredakis et al. 2020).

The aim of this study was to develop a software platform for VR testing that provides as little stimulation – apart from the actual movement – as possible to overcome the bias of testing based on entertainment software. Therefore, allowing to shed light on reasons leading to SS enabling to aid adoption of VR in the medical field. Furthermore, the design of the platform should be easy to modify to be adapted to the ongoing development in VR and to fit as many use cases as possible.