OK, opticians on E2 will know that the area of what your eye sees that is actually in
focus at any one moment is about the size of a
quarter held at arms length. That said, try this next time you have a chance to do some '
grooming'.
Stand in fromt of the mirror, with your face about 35-40 cm away from the glass. Stare at the space between your reflection's eyes. Try not to let your eyes leave this spot, and blink as little as possible. After a few seconds you will start to notice that you reflection's features are dissapearing. The mouth goes first, followed by the nose and most of the eyes. It is similar in effect to those blind-spot tests, but much more drastic.
Quite fun when you're drunk too.