A-MIrror: Augmented Reality Mirror System for Enhanced Visual Illusion in Post-Stroke Upper-Limb Rehabilitation

Paper Title

A-MIrror: Augmented Reality Mirror System for Enhanced Visual Illusion in Post-Stroke Upper-Limb Rehabilitation

Publication Info

• Topic area: Augmented reality systems for post-stroke rehabilitation.
• Keywords: Mirror therapy, augmented reality, post-stroke rehabilitation, upper-limb recovery, embodiment, visual illusion, digital rehabilitation, motivation, user experience, gamification.

Background and Problem

• Problem / challenge: Traditional Mirror Therapy (MT) for post-stroke upper-limb rehabilitation requires professional supervision and often leads to low patient motivation. Digital MT systems address some limitations but compromise the sense of embodiment critical to MT’s effectiveness.
• Significance: Stroke is a leading cause of disability worldwide, and effective, independent rehabilitation solutions are crucial for long-term recovery, especially in home or community settings.
• Motivation and related work: Traditional MT is effective but limited by accessibility and monotony. Digital MT systems, such as Screen-Based Displays (SBDs) and Head-Mounted Displays (HMDs), improve engagement but reduce embodiment due to visual and sensory mismatches. Augmented reality mirrors, particularly Reflective Half-Mirror Displays (RMDs), have not been explored for MT despite their potential to combine embodiment and digital benefits.

Solution

• Proposed approach: A-MIrror, an augmented reality mirror system that integrates a semi-reflective mirror, digital screen, and dual cameras for eye and hand tracking, creating a visual illusion of real and mirrored hands interacting with virtual objects.
• Novelty:
  1. Combines traditional mirror embodiment benefits with digital guidance and gamification.
  2. Introduces "bimanual" tasks to enhance visual illusion and engagement.
  3. Provides training tasks based on Activities of Daily Living (ADLs) for practical rehabilitation.
  4. Demonstrates superior illusion latency and motivation compared to traditional and VR-based MT systems.
• Procedure and key techniques:
  • Eye and hand tracking using RealSense and Leap Motion sensors.
  • Real-time rendering of virtual objects aligned with user perspective and hand movements.
  • Gamified training tasks with visual progress indicators.
  • Iterative design informed by subject matter experts (SMEs) in rehabilitation, serious games, and human-computer interaction.

Results

• Concrete findings:
  • A-MIrror achieved comparable visual illusion frequency (92%) to traditional mirrors (88%) and significantly outperformed VR systems (55%).
  • Reduced illusion latency (4.79 seconds) compared to traditional mirrors (6.89 seconds) and VR systems (7.43 seconds).
  • Higher motivation scores (IMI: 5.28) compared to traditional mirrors (4.35) and VR systems (4.27).
  • Usability rated as "B" grade (SUS score: 70.71).
• Advantage over baselines:
  • Comparable embodiment benefits to traditional MT and superior to VR-based MT.
  • Enhanced motivation and user experience compared to both traditional and VR systems.
  • Faster illusion onset due to guided virtual objects and gamification.
• Experiments / evaluation:
  • Participants: 14 post-stroke patients and 8 therapists.
  • Design: Within-subject comparison of A-MIrror, traditional mirrors, and VR-based MT.
  • Metrics: Visual illusion frequency and latency, Embodiment Questionnaire (EQ), System Usability Scale (SUS), Intrinsic Motivation Inventory (IMI), and therapist credibility/expectancy ratings.
• Limitations and future work:
  • Small sample size and limited task variety.
  • Lack of long-term clinical trials for motor function recovery.
  • Higher hardware costs compared to traditional MT.
  • Future plans include using 3D monitors, expanding task sets, and conducting longitudinal studies.

Summary

A-MIrror is an augmented reality mirror system designed to enhance post-stroke upper-limb rehabilitation by combining the embodiment benefits of traditional mirror therapy with the engagement and guidance advantages of digital systems. It uses dual cameras for eye and hand tracking to create interactive visual illusions, supporting "bimanual" tasks and gamified ADL-based training. Evaluation with patients and therapists showed that A-MIrror achieves comparable embodiment to traditional mirrors, faster illusion onset, and higher motivation, making it a promising tool for independent rehabilitation. Future work will address scalability, task diversity, and long-term clinical validation.