During last lesson of multimedia we learnt about fovea, the small region of eye which has the highest concentration of cones, and therefore responsible for our better central vision.
The amount of space we can sharply recognize due to fovea is about four inches: very smaller than the computer screen itself.
Paraphrasing Sparks: "this is an awful waste of rendering time". So I thought that it could be brilliant to track the eye movement and render at high quality only what's displayed on the fovea.
Well, it's so brilliant that have been already developed. Damn.