User-Centered Formative Evaluation of Cognitive Rehabilitation Software: Cognitive Walkthrough and System Usability Scale Study.

BACKGROUND: The usability of software as a medical device plays a critical role in ensuring patient safety, clinical effectiveness, and treatment adherence. Particularly in tablet-based cognitive rehabilitation software, poor usability can increase the risk of user errors, cognitive overload, and low engagement, which may diminish therapeutic outcomes. Despite the growing integration of cognitive rehabilitation software in clinical settings, few studies have systematically evaluated its usability using structured human factor methodologies. OBJECTIVE: This study aimed to conduct a formative evaluation of a tablet-based cognitive rehabilitation software by identifying potential user errors, interface design issues, and opportunities for improving the user experience and user interface (UI). METHODS: Following the International Electrotechnical Commission (IEC) 62366-1 framework for usability engineering, a formative evaluation was conducted using a combination of cognitive walkthrough (CW) and the System Usability Scale (SUS). CW was used to identify interaction breakdowns and potential use-related problems through scenario-based expert evaluation. The SUS was administered to quantitatively assess perceived usability. Five occupational therapists with experience in cognitive rehabilitation participated in the formative evaluation. RESULTS: A total of 14 usability issues were identified across 6 task scenarios. Common problems included difficulty locating buttons, insufficient feedback during task completion, and inconsistent UI behavior. Key improvement areas included keypad layout, visibility of task progress, and accessibility of help content. The mean SUS score was 73.5 (SD 11.4), indicating an acceptable usability level (grade of B-). The lowest scores were related to system complexity and interface integration, suggesting a need to optimize UI flow and content hierarchy. CONCLUSIONS: The combined use of CW and the SUS enabled the identification of both objective and perceived usability challenges in the cognitive rehabilitation software. Findings emphasize the importance of user-centered design and formative evaluation in the early stages of software development. Recommendations such as improving information visibility, reducing unnecessary steps, and enhancing system feedback may contribute to safer and more effective digital cognitive interventions. However, given the small and homogeneous participant sample and the controlled test environment, these findings should be interpreted as preliminary. This study highlights the practical application of the IEC 62366-1 framework in evaluating software as a medical device and demonstrates its utility in guiding iterative user experience and UI improvements in cognitive rehabilitation contexts.