I see eye contact as sort of an approximation. I think it's less than "my left eye and your right are are staring on parallel lines, and my right eye and left eye are staring on parallel lines". I don't think anyone can truly be that perfect...
I think it wold still be eye contact for example, if two people were focusing on staring at the bridge of each other's noses, directly between each other's eyes...
I think perhaps it might be more than "our eyes are in each other's peripheral vision" which could merely reflect ONE eye seeing an eye, but without the other. Like when things are fuzzy and out of focus when they do not coincide with both eyes' fields-of-view.
The problem with that of course, is that is how everything looks to someone with one eye, which would make them immune to eye contact by that definition (needing 2 eyes' focus).
I wonder if one of the Fantasy-line books has any guidelines on how to cover a sort of Perseus v. Medusa sort of fight where "I can look at your body fine but I must avoid looking at your eyes as I try to decapitate your neck" is a requirement.
It seems like you could rate this in degrees where an Affliction requires:
1) target observes my hex (+4)
2) target observes my chest (-0)
3) target observes a limb (-2)
4) target observes an extremity (-4)
5) target observes my neck (-5)
6) target observes my nose (-6)
7) target observes my eye (-9)
The harder something is to observe, the easier it should be to intentionally (or even unintentionally) avoid observing it, so it should be a higher-value limitation.
Mechanically maybe if you want to avoid something the problem with a basic penalty to perception is it still makes more-perceptive characters more-vulnerable. That makes sense for accidental exposure (you don't know to avoid the Gorgon's Gaze) but not for intentional avoidance: you should actually be better at avoiding the gaze because you're more perceptive of other cues as to where her eyes might end up, like the movements of the torso+neck indicating that.