An autostereogram is a single-image stereogram - a two-dimensional image intended to trick people into believing a three-dimensional image is present, using the same techniques as a "magic eye" picture.
Autostereogram. The books are called MAGIC EYE, I remember them as a kid and was just thinking about them the other day. lol
The usual meaning of the phrase 'jumped out' is when an image or an idea suddenly becomes clear to you. Have you ever looked at an autostereogram (a 'magic eye' picture). You look and you look - and you see nothing but a blur of colour. And then suddenly the picture 'comes'.
I think you are referring to a random dot autostereogram. They look like random dots unless you diverge your eyes, at which point, a stereo picture of an object appears. Ssome people can find the image by just crossing their eyes, then letting them relax slowly. Others imagine different distances (pretend to look through the page) until they see the stereo image. At some point you will see a stereo image within the colors of the page (they don't have to be colored, but usually are). The colors will not be the colors of the object... There was a company called Magic Eye that published some books of these sort of images in the early to mid 1990's. Google for autostereogram and you should be able to find some examples.
If by uncomfortable you mean the way they sit on your face, and if your referring to movie theater glasses, its because they're a one size fits all template. They are they stiff and don't alight well with the contours of your face. If your referring to uncomfortable in terms of making you dizzy at times, its because when you watch 3D movies both of irises of your eyes must be at a fixed point causing your eyes to cross for pretty much the whole movie. Therefore, sometimes possibly making you feel kinda queasy.