###### Abstract  
This study explores the application of Eye-Tracking technology for the ergonomic evaluation of assistive device usability. Sixty-four participants evaluated six jar-opening devices in a two-phase study. First, the participants' gaze was recorded while they viewed six rendered pictures of assistive devices, each shown in two different versions: with and without rubber in the grip area. Second, the participants physically interacted with the devices in a hands-on usability task. In both phases, participants rated the devices according to six usability affordances: robustness, comfort, easiness to grip, lid slippery, effort level, and easiness to use. Eye-Tracking metrics (fixation duration, number of fixations, and visit duration) correlated with the on-screen ratings, which aligned with ratings after using the physical devices. High ratings in comfort and effort level correlated with more visual attention to the grip area, where the rubber acted as key signifier. Heatmaps revealed the grip area as important for comfort and easiness to use and the lid area for robustness and slipperiness. These findings demonstrate the potential of Eye Tracking in usability studies, providing valuable insights for the ergonomic evaluation of assistive devices. Moreover, they highlight the suitability of Eye Tracking for early-stage design evaluation, offering objective metrics to guide design decisions and improve user experience. e 2025 23 June 2025 23 July 2025 25 July 2025 23 July 2025 23 July 2025 23 July 2025 23 July 2025 23 June 2  
must grasp how a product operates through clear, effective communication from the device itself. In other words, the use of an AD must be intuitive. Product communicative functions [19] include indicative functions (technical and practical) and symbolic functions (cultural and historical messages). [PERSON] [20] proposed a theoretical framework for designing products that clearly communicate their functionality, aligning with users' mental models and prior experiences. [PERSON]'s Fundamental Principles of Interaction emphasise concepts such as affordances, signifiers, constraints, mapping, and feedback, derived from [PERSON]'s [21] affordance theory but applied within product design contexts to ensure user understanding and usability. Affordances refer to the possible actions a product allows, enabling users to perform desired tasks. In the context of this study, we adopt a broader, operational use of the term affordance, referring to perceivable product characteristics that shape users' expectations about how easily and effectively a device can be used. To further justify our broader use of the term, the recent literature in product and environmental design recognises affordances as relational properties between product characteristics and user capabilities, extending beyond the original theoretical definitions [22; 23; 24]. In this sense, aspects such as comfort or ease of grip, when perceived as enabling or facilitating user action, can be interpreted as affordances within an application-oriented framework. When affordances are not immediately clear, signifiers--design elements capable of communicating opportunities for product use--should be employed. Using signifiers is the most effective way to reveal affordances and ensure users understand how to interact with the product [20]. Building on these principles, [PERSON] and [PERSON] [25] explored the inter-relationships between perceived product meanings, proposing an 'interactionist framework' in which product forms guide user responses along dimensions such as'repulsive or inviting for interaction' and'readiness for interaction.' Their study, using hard drive and soap dispenser prototypes, highlights how product meanings are interconnected and influence usability, suggesting that designers should strategically assign meanings to product forms to enhance user interaction and comprehension.