I am very cross-eyed at the moment (surgery resulted in both my eyeballs moving) and require a little plastic "stickon" that goes on the left lens of my glasses; which has prisms to redirect the light so that both eyes are looking in the same direction (prisms are fairly normal; it's the _amount_ of correction I need that is abnormal).

The correction on the left lens is so bad that looking through it is completely blurry (with lots of rainbows if I'm looking towards a light). However, when looking through my glasses with both eyes, everything appears normal. I can see in stereo (which I cannot do w/o the correction) and everything is in focus. There is still _some_ rainbow effect.

So, my brain is taking the "clear image" from my right eye and overlaying it with the distance information that the left eye adds to that... but ignoring the blurry image from the left eye completely.

Honestly, I find it mind boggling.