[evolvingstuff]

Agreed. To elaborate:

Saccades to an unexpected stimulus normally take about 200 milliseconds (ms) to initiate, and then last from about 20–200 ms, depending on their amplitude (20–30 ms is typical in language reading).

Saccades of 20ms in duration are ones that are very near to the current center of focus (e.g. moving to the next chunk of letters while reading the words of this sentence). This just means that detailed rendering needs to extend to a slightly larger radius, but this is still significantly cheaper to render than an field of view. For larger jumps there is ~200ms during which the computer can attempt to predict the final destination of the saccade, and thus begin to do some preemptive computations. Once the saccade lands at the new location, assuming a rendering speed of 100fps, there would be at most 10ms before the high-res version kicked in, but again, with some degree of preemptive/predictive computation, perhaps a slightly better version could be available immediately.