Another thread made me read more about saccadic masking.

Every time you move your eyes (and they are moving all the time), your brain switches off the processing of retinal images. When the movement stops, the processing starts again. During that time you're effectively blind. It's called saccadic masking.

If this didn't happen, you'd see blurred images every time your eyes move.

Our field of vision seems to be continuous due to a phenomenom known as transsaccadic memory. The brain takes in the image obtained just before the saccadic mask sets in, and the image it gets when the mask is lifted. It then integrates these two images to fill in the gap.