One of the things I have learned from Dr. Paul Canali is that by watching the eyes of someone on the massage table, you can tell so much. When a person is deep in the subconscious (or hippocampus), the brain is processing information and neural connections and neural pathways. The eyes have a movement that when you see it, you will know exactly where they are. This movement also signals that the person has moved past the fears and into the processing stage. By working with this, you can help assist and provide safety to the person as they process things that they may not readily think about or things that are in the conscious mind. This work allows you help the person move through some very traumatic experiences without having to completely relive all the horror and pain of those events in a conscious manner. It is very powerful and amazing to work with.
Here's an article that talked about some of the studies being done in this area.