Complex sentence: It doesn't mean that our vision becomes crippled due to saccadic masking--it becomes crippled due to saccadic movement itself; the masking is there to shield our limited brain processing capacity from being bothered with an otherwise useless blurred image.
Split into simpler sentences: It doesn't mean that our vision becomes crippled due to saccadic masking. Rather, it becomes crippled due to saccadic movement itself; the masking is there to shield our limited brain processing capacity from being bothered with an otherwise useless blurred image.