I learned it to an unlighted runway. As soon as you see the runway (or just anything for the matter) in the beam of the landing light, flare. Worked like charm. Depth perception is the same as during the day. It stops more or less at 10m. From there on it is experience of the brain. Therefore the more night autos you do the more they give you the same sight picture you are comfortable with during the day. Except for a lot less details and in the peripheral vision there is just nothing (except the grinning face of that sadistic CFI). That makes judging the hight more difficult.
It is rather useless to do night autos to a lighted runway. There will never be one, when you need it the most. It is an emergency procedure after all.