The natural result of sense contact is feeling. This is the automatic response to each object which arises. Feeling is of three kinds; pleasant, unpleasant or neutral. It is the immediate judging quality which sorts all experience into categories in relation to the perceived interests of an ego. Put simply, each object which arises is either wanted, unwanted or indifferent.
Feeling is a very primitive level of mind. It is easy to see how this response is a necessary function for beings to survive in the world. All our more complex emotions are constructed on the foundation of these three fundamental feelings.
Feelings can vary in intensity from very subtle to overwhelming. The image here is of a man with an arrow in his eye, aptly illustrating how feeling enters through the door of the senses and can pierce us to the quick.