Your eyes use a convex lens to make images on your retina, but the image produced is upside-down. Of course we don’t see the world as upside down, so what happens to the upside-down image made on the retina? The image is transferred through the optic nerve and is interpreted by the brain. The brain understands how to turn the image over so that it looks like the real world.

Upside - Down World!

Once there was a man who volunteered to wear glasses that made everything seem upside-down to him...after a period of time, his brain figured out how to flip everything over so that he could see normally...guess what happened when he took the glasses off? The world was all upside-down again! His brain had to re-learn, again, how to see things correctly!

This picture below shows the process images go through.