Or maybe he didn't need peripheral vision because he could stop nearly any attack that hit him. At that point, he wouldn't need peripheral vision to kick the crap out of his "sneaky" attacker.
Just sayin... peripheral vision seems kind of pointless when you gain the ability to shrug off tank rounds.
As for how Horus is depicted (noble and graceful vs. hateful and maniacal like in that piece of artwork), I think it exaggeratedly symbolizes his transformation.
