Imagine having this
suddenly obscuring your vision.
Now imagine that every line in that zigzaggy bastard is flashing in different colours, and that around the edges of the whole thing is a blind spot.
And imagine that the whole thing is growing larger, moving from a tiny spot in the middle of your field of vision, till it occupies your entire peripheral vision.
I hate these damn things. But OH MY GOD I'm so grateful I don't get the accompanying migraines.