Smartglasses can provide safety-relevant information during tasks, e.g., by displaying warnings or important updates during search operations in crisis management, or about patients while treating them in healthcare. It is both necessary for the desired outcomes and frequently taken for granted that users perceive these messages reliably and in a timely manner. However, research on inattentional and change blindness has shown that visual stimuli—even “obvious” stimuli directly “in front of one’s eyes”—can be overlooked. Thus, in safety-critical situations, in which the user is focused on a task in the environment, instructions or warnings can be overlooked, despite being displayed in the user’s field of view—with potentially serious consequences. In this paper, we address the problem of taking perception of messages displayed on smartglasses for granted with respect to perceptual load theory. We present the results of a study comparing reaction times to smartglasses messages in conditions of low and high perceptual load with 24 participants in order to analyze how well users can notice messages in different load conditions. We also describe the implementation of an application to conduct these studies and possible designs for future studies.