Different restaurants, it appears, take different approaches:
Some use waiters with night vision goggles and put masks over the eyes of the customers. Others set up a "light-lock" (such as Opaque, referred to in the previous post) and have visually handicapped waitstaff.
Most of my friends consider this a bit kitschy - they don't see the appeal - but I figure that it's worth a try (especially since the dark dining restaurants in the US will run $100+, compared to $50-75 in some places in Europe!)