Normal human vision is an unbelievably complex and sophisticated thing. Here is a special issue of Vision Research on one tiny component of vision - fixational eye movements and perception:
During viewing of a stationary scene, rapid gaze shifts, known as saccades, occur every few hundreds of milliseconds. Saccades separate fixations, the periods of apparent eye immobility in which visual information is acquired and processed. Close inspection of oculomotor activity in these periods reveals, however, that the very world “fixation” is misleading: small eye movements incessantly occur in the inter-saccadic intervals, suggesting an even deeper coupling between visual functions and oculomotor activity. These gaze shifts come in different varieties and are collectively known as fixational eye movements. Although humans are normally not aware of making them, they displace the retinal image at speeds that would be clearly visible had the motion originated from the visual scene rather than the observer.