IUBio

Cross - Wired Eyes

Marielle Fois im99_foa at nada.kth.se
Sun May 13 11:56:05 EST 2001


On Sun, 13 May 2001, Karl Self wrote:

>     What is the difference between "eyes" and "halves of the visual field"?

The difference is simple. Wherever you look, what you look is your
visual field. Divide it by a vertical line in front of your nose, and
you will have the left and right visual hemifields. What is meant by
the eyes, is indeed the optical nerves. From each eye, two optical
nerves go to the brain, one of them carrying the information of the
left hemifield, and the other the information of the right hemifield.
So each eye captures information of both hemifields; that's how depth
sensation is achieved.

The retina is divided in two halves. It is easy to imagine, given the
curved disposition of the retina, that the left halves of the retina
perceive the right hemifield, and the right halves the left
hemifield. Physically it is impossible the contrary to happen, unless
we had the retina at the front of our eyes instead of at the back. In
addition, what is perceived by the left half of the retina of the
left eye and the right half of the retina of the right eye, is the
same.

Marielle




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