Darkness Vision is a skill taught at Exillium. It is said that you focus on the light and let your brain enlarge it to create a much lighter environment. Sophie and her friends learn the skill while attending Exillium in Neverseen.
The trick is to remember that there is light everywhere, no matter how dark it seems, and to let your brain amplify those small amounts of light. Concentrating and thinking thoughts of the light opens your mind and lets you see.