Task Dynamics Modulate Discomfort from Vertical Misalignment in See-Through Augmented Reality

The rapid expansion of Augmented Reality (AR) technologies has increased the need to ensure visual comfort during extended, real-world use. In optical see-through AR systems (OST-AR), users perceive the real environment without mediation, whereas inaccuracies in the rendered virtual content can lead to perceptual conflicts with the real-world view. One such issue is Binocular Vertical Misalignment (BVM), which adds vertical disparity to augmented content while leaving the real-world view unaffected. Existing research on BVM relies on restricted stereoscopic displays and static stimuli, limiting ecological validity for real-world AR applications. In this study we investigate the effects of BVM directly on a see-through AR device, during prolonged (30-minute), interactive usage sessions. Our methodology incorporates individually calibrated BVM thresholds and evaluates discomfort across two distinct scenarios: a search and navigation task involving ego-motion and a stationary manipulation task. Visual discomfort was assessed using questionnaires and in-task Likert-scale ratings collected throughout the session. Experimental results indicate that perceived discomfort scales with a user's individual tolerance threshold rather than the absolute magnitude of misalignment. Notably, the navigation task significantly exacerbated discomfort compared to the manipulation task, highlighting the critical role of task dynamics in BVM perception. These findings suggest that visual comfort in AR is a multi-faceted interaction between hardware-induced disparity, user tolerance, and specific task demands. This work provides foundational insights for designing more comfortable, long-term wearable AR experiences and informs calibration requirements for OST-AR displays.