Retinal image slip

Recall that eye movements contribute both to maintaining a target in a fixed location on the retina (smooth pursuit, VOR) and also to changing its location slightly to reduce perceptual fading (microsaccades). During ordinary activities (not VR), the eyes move and the image of a feature may move slightly on the retina due to motions and optical distortions. This is called retinal image slip. Once a VR headset is used, the motions of image features on the retina might not match what would happen in the real world. This is due to many factors already mentioned, such as optical distortions, tracking latency, and display scanout. Thus, the retinal image slip due to VR artifacts does not match the retinal image slip encountered in the real world. The consequences of this have barely been identified, much less characterized scientifically. They are likely to contribute to fatigue, and possibly VR sickness. As an example of the problem, there is evidence that microsaccades are triggered by the lack of retinal image slip [72]. This implies that differences in retinal image slip due to VR usage could interfere with microsaccade motions, which are already not fully understood.