Hi bluesnowflake, fields is where they test to see if you can see properly over the whole visual field.
you stare into a sort of half globe thing (unless the one I was tested on was old fashioned LOL!) anyway, tiny bright, less bright and dim lights come on briefly one at a time all over the inner surface and you sit there with your chin on a rest staring into the thing, straight ahead, and trying not to blink
Every light you see, you press a button. They get a map of your visual field from this and can tell if there is an area you cant see or see dimly. good luck!
fields test 
Linear Mode
