According to a study published in July 2012 Archives of Surgery, only about 25% of eye institutions had a policy of informing patients that residents would be involved in their surgery! The reasoning of these teaching facilities is that it is critical that residents learn how to do surgeries and that if patients were offered the choice of not having a resident involved in their surgery, that most would not want them.
This is deceptive and unethical. Patients have the right to know if their doctor will be doing their surgery or if some trainee would be slipped in behind their back! These institutions have the obligation of informing patients when they are planning to use residents in surgical operations.