Mixed reality (MR) is a collective term for technologies that merge the real and the virtual. In medical applications of MR technologies, research is in progress for applications in surgical procedure simulation systems designed for therapy and medical training and increasing proficiency in fields such as ophthalmology, brain surgery, and orthopedic surgery. MR rehabilitation holds the potential for substantial advances and contributions in respect to therapeutic efficiency, recovery from psychosomatic disorders, and heightening of patient desire, motivation, and acceptance through the patient’s own appraisal of physical and mental disability. This study focused on the development of a medical device system using a head mounted display (HMD) for examination and treatment of the visuospatial cognitive disorder known as unilateral spatial neglect as an illustration of MR rehabilitation.