AI Pawn Sense and Darkness

So my question is, how do I control the “sight radius” variable from the blueprints section? Or is this even a feature?
I am creating a stealth aspect in my game and need guards to not see me in the dark, that is, I need their vision to be more than halved. I have ideas on how to do this with triggers in the light, I just need something which will adjust the AI sight accordingly.

Thanks!