Stephen Lang wore contact lenses that greatly restricted his vision, particularly in low light. The other actors, in the scene taking place in the dark, wore lenses that made them look like they had dilated pupils but also greatly restricted their vision.
In contrast to his previous work on Evil Dead, director Alvarez decided this movie would have less blood, an original storyline, more suspense, and no dependence on spooky supernatural elements - which he felt was currently overused.
The address for the house used to film the exterior shots of the Blind Man's home is actually 2488 Buena Vista St, Detroit, MI 48238. When looking at the street view on Google Maps, most of the neighboring houses appear to be abandoned, just like in the movie. In fact, it doesn't look like anything about this location was changed for the sake of filming.
The trivia items below may give away important plot points.
Throughout the movie you can see areas in the house where crosses used to be but have been taken down. Later in the film The Blind Man states that there is nothing men cannot do once they've accepted there is no god.
The creators of the film initially had an even darker ending in mind. Rocky (Jane Levy) was not supposed to make it out of the house. Instead, the Blind Man (Stephen Lang) locks her up in a cell, and even though the police come to investigate the burglary, they miss the door to her cell. The writers thought that this ending was too downbeat, so they changed it to Rocky escaping, but the Blind Man getting away with his crimes.
Christian lore tells of a devil sitting on your left shoulder, whispering evil, and an angel on your right shoulder, whispers good. Money, the bad influence, is standing on Rocky's left when he dies. Alex, who tried to get Rocky to walk away and later tries to save her, is standing on her right, when he dies.