I've personally experienced this decoupling of vision and second sight. When I've had bad migraines in the past, I typically experience scintillating scotoma, which isn't that unusual.

But the odd thing is: even though I can visually "see" certain objects, I don't feel like I'm observing them. For example, I can look directly at text on my screen, but have a difficult time reading the text. It's quite an odd experience.