What a tracer should look like (before spazzing just look).

[Heliocon]

Ok I am not reading all this crap but first off no matter who says it - anyone claiming to have RL experience take with a grain of salt, it is the internet. That being said what winny is saying is up to page 9 (stopped there) is correct to an extent. As for the 2d the problem there is that you have 2 eyes that the brain uses to create a 3d image, even though each eye can only see in "2d" individually.
The effect of the trail being left in your eye WOULD occur if you stared at it/focued on it, it would "burn" an image into your retina (desensitizes or overloads certain receptors, cant remember the actual biology of it) just like staring at a lightbulb and then closing your eyes. But you would have to be focusing on the round for it to remain in your vision in that way.

Also wouldnt higher calibre rounds have a larger base and more area emitting light? I dont know (thats why I am asking lol).