One major benefit of wearable computers is that users can naturally move and explore computer-mediated realities. However, researchers often observe that users' space and motion perception severely differ in such environments compared to the real world, an effect that is often attributed to slight discrepancies in sensory cues, for instance, caused by tracking inaccuracy or system latency. This is particularly true for virtual reality (VR), but such conflicts are also inherent to augmented reality (AR) technologies. Although, head-worn displays will become more and more available soon, the effects on motion perception have rarely been studied, and techniques to modify self-motion in AR environments have not been leveraged so far. In this paper we introduce the concept of computer-mediated optic flow, and analyze its effects on self-motion perception in AR environments. First, we introduce different techniques to modify optic flow patterns and velocity. We present a psychophysical experiment which reveals differences in self-motion perception with a video see-through head-worn display compared to the real-world viewing condition. We show that computer-mediated optic flow has the potential to make a user perceive self-motion as faster or slower than it actually is, and we discuss its potential for future AR setups.