All owls have large eyes and ears compared to the size of their faces. The round, disc shape of the face is used to capture sound, and the ear is the size of the disc on each side of the head, with a very large hole, compared to the size of the head, for the sound to enter into. These holes are set at slightly different angles on each side of the head which gives the bird stereo sound vision. If you imagine two lines of sound entering the ears at different angles, then follow the lines back to the sound maker, where the lines of sound cross is where the little mammal will be located. For this reason, they do not need a good light source to catch their prey.
Owls eyes are slightly conical in shape, spreading out at the back of the eye, and they are unable to move their eyes (but do have control on the movement of the iris), so to compensate for this they have extra vertebrae in their necks which allows them to see right behind them, plus a bit further. They are able to see better than we can in very poor light, but they cannot see in total darkness.