Do those who need to keep the backlight as low as possible get adequate natural daylight and sunlight? Personally, I go without sunglasses whenever possible and tolerate bright natural light much better than most others. I have some books on the topic of the benefits of unfiltered natural light on eye and brain health. Contrary to the dogma we're told, it's healthy and necessary for proper development and nurture of the vision system and the brain.
Edit: even normal eyeglasses act like sunglasses in terms of UV filtration: they just allow in more visible light. The eyes and brain are meant to receive unfiltered natural light that is impossible when any lenses are on the eyes except certain contact lenses.
When I wear contacts the ones I like are Dailies Total 1, and they have no UV filtration. They are very soft and very permeable while many traditional lenses have a tendency of suffocating the portion of the eyes they cover.
So in sum, I suspect one can tolerate backlight lighting better if they're used to being outdoors without lenses on.