Effect of the Oculus Rift Head Mounted Display on Postural Stability

IntroductionResearch exploring virtual reality (VR) in healthcare has increased over recent decades with widespread adoption in treatment by professionals evident. A recent development in this field is the Oculus Rift (OR) head mounted display (HMD) developed by the US company Oculus VR(TM). A main characteristic of the OR is its ability to track head movements to allow the user to seamlessly look around the virtual world. The difference between the HMDs mentioned in related work and the OR is that the latter blocks the peripheral vision completely. Furthermore, the OR offers a field-of-view of 90 degrees for each eye, almost twice as much as anything else on the market, resulting in a fully-immersive 3D experience (1). For this study, a developer kit OR unit with a resolution of 640 x 800 pixels per eye was used (2).The primary objective of this study was to investigate how a virtual reality environment (VE), displayed with an OR, impacted balance-impaired adults, aged 59-69, in a control group compared to non-balance-impaired adults, aged 18-28. The setup comprised of (a) a bespoke balance board that controls an animated virtual reality skiing game, especially designed for OR viewing; (b) Microsoft Kinect (camera-based motion sensing device) to measure the angle of sway; and (c) the OR.Balance and the sensory systemsAccording to (3), balance is a concept used to define the interaction between different domains (mechanics, physiology, anatomy, sociology, and psychology). The main points of interest are human stability and sensory systems.Human stability can be defined as the inherent ability of a person to maintain, achieve or restore a state of balance, associated to the sensory and motor systems. Postural control is a requirement to maintain a variety of postures and activities. As a consequence, the control of balance in humans has been acknowledged as three possible broad classes of activities, namely: the maintenance of a definite posture, for example sitting or standing; voluntary movement, for example moving between postures; and reaction to an external disturbance, for example a slip or a push (4).In order to determine the impact of using a HMD related to physical balance, it is necessary to investigate how the sensory systems affect balance. There are three major sensory systems involved in balance and posture: the visual sensory system, which is the main point of interest in this study; the vestibular system; and the somatosensory system (5). The postural control depends on the integration of information received from the proprioceptive, vestibular, and visual sensory systems. It has been shown that extremely low frequencies of sway are best stabilized by vision. Conflicts can also arise between the senses, especially when the visual and/or proprioceptive cues differ from vestibular information (6). Furthermore, Wing et al. (7) state that the variability in the rate of change of centre of pressure also increases during upright standing with eyes closed; the explanation being that loss of vision by closing the eyes usually results in increased sway.Studies in rehabilitation with VE through different HMDsDifferent research articles reveal contentious results regarding conflicts between the sensory systems that affect physical balance when exposed to a VE. For example, Peli (8) investigated the potentially harmful effects on the visual system due to HMD use. When investigating functional changes, experiments were conducted to see if there were any functional changes in binocular vision, accommodation, and resolution when using HMDs compared to monitor displays. The results showed that there were no changes in any of the outcomes. The only mentionable difference was that the HMD was less comfortable than the CRT monitor (difficulty in focusing and postural discomfort). However, subsequent research revealed the contrary as Wenzel et al. (9) found that aircraft workers, who used a HMD for training, testified that there were problems such as eyestrain, headache, nausea and dizziness. …