Conducting with your eyes

My college orchestra director could start a piece effectively without using a baton.  Every now and then, he would give the downbeat by raising his head slightly and taking a short breath.  The orchestra would always respond, partially out of fear.  To challenge his conducting students, he would sometimes ask them to put their hands in their pockets and figure out another way to conduct.  It was interesting watching aspiring conductors start a piece by nodding, blinking, and grimacing.  When you can't conduct with the baton, it challenges you to communicate with the orchestra in subtler ways and forces the orchestra to watch you and decipher your directions.