Why Don't We See a Black Area When We Close One Eye?

[JPC]

Hey

In each eye there is a blind zone, and the eyes complete each others blind zone

But now

how come : when i close one eye, and open one
i don't have any black in the view i have
because the closed eye gives me a totally black image

so on the side of opened eye :
i should have a view with a black area

and on the side of the closed eye :
i should have a black view with an area where i can see a little

but how come that doesn't happen ?

 

[jim mcnamara]

Short answer - your brain is wired to get around the no see zone. It moves your eye (essentially involuntarily) to compensate. Your brain wants to use the fovea to see, if at all possible. It's not adaptive to try to see potential danger using the no see zone of your eye.

And it doesn't usually appear black, just ultra-blurry.

The esasiest way to see it it to get paper with a repeating intricate design, like wrapping paper.

Put it on a wall, stand about two feet away, stare with one eye at one fixed spot in the center of the paper, and you detect an area where you do not see much. That's it.