Beyond Symmetry: A Novel Asymmetric Interaction Strategy for Immersive VR-Based Mirror Therapy

Abstract-Virtual Reality (VR) has been widely applied in healthcare domain. Virtual Reality Mirror Therapy (VRMT) is one such clinical application for phantom limb pain management and post-stroke hemiparesis rehabilitation. However, the prevailing design of VRMT tasks typically follows the schema of traditional mirror therapy paradigm that prescribes strictly symmetric bilateral movements along the body's midline. While symmetry is not a requirement by the mirror neuron therapy where mirror therapies derive, this constraint imposes unnecessary limitations to both the development of diversified game-based rehabilitation tasks and portability of VR equipment and hardware. As a result, average patients using a conventional VR system may often find it difficult to perform certain exercises, such as arm abductions, or not possible to run a VRMT paradigm on affordable VR equipment for home-based rehabilitation. We therefore propose AsymmVRMT, an asymmetric strategy for mirrored affected limb mapping, and adopted it in our VRMT paradigm. We conducted a randomized controlled trial (RCT) on post-stroke hemiparetic patients, and examined their clinical outcome measures (FM-UE, BI & WMFT) along with their user experience data (SUS & VEQ). Results showed that patients demonstrated stronger adaptability and more positive perceptions toward using the AsymmVRMT model, while the therapeutic outcomes were as good as those using conventional VRMT. AsymmVRMT therefore appears to be an effective alternative for human-computer interaction in VR that may offer higher flexibility and diversity to address the hardware-related constraints in rehabilitation system development, facilitating convenient VR-based rehabilitation for patients, both at the hospital and at home.