What’s the meaning of “...”? “Seeing” is “vision” “Compromised” means weakened or not fully functioning.

It sounds like it's a philosophical book which talks deeply and the brain and mind. Therefore, it's quite difficult to interpret. However, it could mean that, when you see something, it is not actually what the brain thinks it is. Or, that the brain tells you that what you see isn't actually what you can actually see (reality).