Posted by Jocelyn on August 24, 1999 at 08:37:54:
The blind spot is an area on the retina without receptors.
Therefore any image that falls on this region will NOT be seen. In
this region, the optic nerves come together and exit the eye on
their way to the brain. The following demonstrates this effect:
Take a strip of paper, about 15cm long, and 3 can wide, use a
marker to mark a cross at one end, and a bold dot at the other
end.
Close your left eye. Then move about 20 inches away from your
paper.Look at the dot with your right eye. Slowly move your head
closer while looking at the dot. At a certain distance, the + will
disappear from sight.this is when the + falls on the blind spot of
your retina.
Note: Do not stare at the + sign deliberately