Darkvision only really functions properly in near complete darkess...which doesn't exist in too many places in Layonara. Most characters have light sources on their persons, like robes, swords and other items that give off a glow.
Darkvision (and to a lesser degree, low-light vision) will get interrupted/switched off if the light around the character, ambient and sourced light, is too bright...and for those abilities, "too bright" really isn't very bright at all.
You don't have to do anything really to have this work...except for be in a very dark place.