A UI for a HMD system includes a HMD configured to be worn by a surgeon. A tracker is configured to track head gestures by the surgeon. A footswitch is configured to detect foot motion inputs by the surgeon. A computer couples to the HMD, the tracker, and the footswitch. A user interface includes the HMD, tracker, and footswitch. The use interface is configured to: provide to the computer the head gesture in association with the foot motion input, and display an image relating to a surgical procedure on the HMD. The computer is configured to: apply the head gesture received in association with the foot motion input to perform a first action on the HMD system when the HMD system is in a first system mode, and perform a second action on the HMD system when the HMD system is in a second system mode.