We propose a novel method to estimate the object that a user is focusing on by using the synchronization between the movements of objects and a user's eyes as a cue. We first design an event as a characteristic motion pattern, and we then embed it within the movement of each object. Since the user's ocular reactions to these events are easily detected using a passive camera-based eye tracker, we can successfully estimate the object that the user is focusing on as the one whose movement is most synchronized with the user's eye reaction. Experimental results obtained from the application of this system to dynamic content (consisting of scrolling images) demonstrate the effectiveness of the proposed method over existing methods. Keywords- event-based gaze estimation, synchronization, dynamic content, eye movement